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Sample records for magnetic flux tubes

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Wave function properties of a single and a system of magnetic flux tube(s) oscillations

    NASA Astrophysics Data System (ADS)

    Esmaeili, Shahriar; Nasiri, Mojtaba; Dadashi, Neda; Safari, Hossein

    2016-10-01

    In this study, the properties of wave functions of the MHD oscillations for a single and a system of straight flux tubes are investigated. Magnetic flux tubes with a straight magnetic field and longitudinal density stratification were considered in zero-β approximation. A single three-dimensional wave equation (eigenvalue problem) is solved for longitudinal component of the perturbed magnetic field using the finite element method. Wave functions (eigenfunction of wave equation) of the MHD oscillations are categorized into sausage, kink, helical kink, and fluting modes. Exact recognition of the wave functions and the frequencies of oscillations can be used in coronal seismology and also helps to the future high-resolution instruments that would be designed for studying the properties of the solar loop oscillations in details. The properties of collective oscillations of nonidentical and identical system of flux tubes and their interactions are studied. The ratios of frequencies, the oscillation frequencies of a system of flux tubes to their equivalent monolithic tube (ω sys/ω mono), are obtained between 0.748 and 0.841 for a system of nonidentical tubes, whereas the related ratios of frequencies for a system of identical flux tubes are fluctuated around 0.761.

  12. 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.

  13. 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.

  14. Plasma dynamics on current-carrying magnetic flux tubes

    NASA Technical Reports Server (NTRS)

    Swift, Daniel W.

    1992-01-01

    A 1D numerical simulation is used to investigate the evolution of a plasma in a current-carrying magnetic flux tube of variable cross section. A large potential difference, parallel to the magnetic 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.

  15. 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.

  16. The equilibrium structure of thin magnetic flux tubes. II. [in sun and late stars

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    The thermal structure of the medium inside thin, vertical magnetic flux tubes embedded in a given external atmosphere is investigated, assuming cylindrical symmetry and a depth-independent plasma beta. The variation with tube radius of the temperature on the tube axis is computed and the temperature on the tube wall is estimated. The temperature variation across the flux tube is found to be due to the depth variation of the intensity and to the density stratification of the atmosphere. Since the temperature difference between the axis and the wall is small in thin flux tubes (of the order of 10 percent), the horizontal temperature gradient may often be neglected and the temperature in a tube of given radius may be described by a single function of depth. Thus, a more detailed numerical treatment of the radiative transfer within thin flux tubes can be substantially simplified by neglecting horizontal temperature differences within the flux tube proper.

  17. Propagation of nonlinear, radiatively damped longitudinal waves along magnetic flux tubes in the solar atmosphere

    NASA Technical Reports Server (NTRS)

    Herbold, G.; Ulmschneider, P.; Spruit, H. C.; Rosner, R.

    1985-01-01

    For solar magnetic flux tubes three types of waves are compared: longitudinal MHD tube waves, acoustic tube waves propagating in the same tube geometry but with rigid walls and ordinary acoustic waves in plane geometry. It is found that the effect of the distensibility of the tube is small and that longitudinal waves are essentially acoustic tube waves. Due to the tube geometry there is considerable difference between longitudinal waves or acoustic tube waves and ordinary acoustic waves. Longitudinal waves as well as acoustic tube waves show a smaller amplitude growth, larger shock formation heights, smaller mean chromospheric temperature but a steeper dependence of the temperature gradient on wave period.

  18. HOW MUCH DOES A MAGNETIC FLUX TUBE EMERGE INTO THE SOLAR ATMOSPHERE?

    SciTech Connect

    Magara, T.

    2012-03-20

    The emergence process of the magnetic field into the solar atmosphere plays an essential role in determining the configuration of the magnetic field and its activity on the Sun. This paper focuses on how much the magnetic flux contained by a flux 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 flux 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 magnetic field such as the radius of a flux tube, field strength, field-line twist, and wavelength of undulation assumed by the flux tube. We also discuss the relationship between magnetic configurations and their stability on the Sun.

  19. Sausage Instabilities on top of Kinking Lengthening Current-Carrying Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; You, Setthivoine

    2015-11-01

    Observations indicate that the dynamics of magnetic flux 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 magnetic flux tubes. Current driven flux tubes evolve over a wide range of aspect ratios k and current to magnetic flux ratios λ . An analytical stability criterion and numerical investigations, based on applying Newcomb's variational approach to idealized magnetic flux 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 flux tubes. A triple electrode planar plasma gun (Mochi.LabJet) is designed to generate flux tubes with discrete core and skin currents. Measurements from a fast-framing camera and a high resolution magnetic probe are being assembled into stability maps of the k - λ space of flux tubes. This work was sponsored in part by the US DOE Grant DE-SC0010340.

  20. Dynamics of Magnetic Flux Tubes in an Advective Flow around a Black Hole

    NASA Astrophysics Data System (ADS)

    Deb, Arnab; Chakrabarti, Sandip Kumar; Giri, Kinsuk

    2016-07-01

    Magnetic fields cannibalized by an accretion flow would very soon have a dominant toroidal component. Without changing the topology, we study the movements of these flux tubes inside a geometrically thick advective disk which undergo centrifugal pressure supported shocks. We also consider the effects of the flux tubes on the flow. We use a finite element method (Total Variation Diminishing) for this purpose and specifically focussed whether the flux tubes contribute to changes in outflow properties in terms of its collimation and outflow rates. It is seen that depending upon the cross sectional radius of the flux tubes (which control the drag force), these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surface). These interesting results obtained with and without flux tubes point to the role the flux tubes play in collimation of jets and outflows.

  1. Nonlinear fast sausage waves in homogeneous magnetic flux tubes

    NASA Astrophysics Data System (ADS)

    Mikhalyaev, Badma B.; Ruderman, Michael S.

    2015-12-01

    > We consider fast sausage waves in straight homogeneous magnetic tubes. The plasma motion is described by the ideal magnetohydrodynamic equations in the cold plasma approximation. We derive the nonlinear Schrödinger equation describing the nonlinear evolution of an envelope of a carrier wave. The coefficients of this equation are expressed in terms Bessel and modified Bessel functions. They are calculated numerically for various values of parameters. In particular, we show that the criterion for the onset of the modulational or Benjamin-Fair instability is satisfied. The implication of the obtained results for solar physics is discussed.

  2. Equilibrium structure of solar magnetic flux tubes: Energy transport with multistream radiative transfer

    NASA Technical Reports Server (NTRS)

    Hasan, S. S.; Kalkofen, W.

    1994-01-01

    We examine the equilibrium structure of vertical intense magnetic flux tubes on the Sun. Assuming cylindrical geometry, we solve the magnetohydrostatic equations in the thin flux-tube approximation, allowing for energy transport by radiation and convection. The radiative transfer equation is solved in the six-stream approximation, assuming gray opacity and local thermodynamic equilibrium. This constitutes a significant improvement over a previous study, in which the transfer was solved using the multidimensional generalization of the Eddington approximation. Convection in the flux tube is treated using mixing-length theory, with an additional parameter alpha, characterizing the suppression of convective energy transport in the tube by the strong magnetic field. The equations are solved using the method of partial linearization. We present results for tubes with different values of the magnetic field strength and radius at a fixed depth in the atmosphere. In general, we find that, at equal geometric heights, the temperature on the tube axis, compared to the ambient medium, is higher in the photosphere and lower in the convection zone, with the difference becoming larger for thicker tubes. At equal optical depths the tubes are generally hotter than their surroundings. The results are comparatively insensitive to alpha but depend upon whether radiative and convective energy transport operate simultaneously or in separate layers. A comparison of our results with semiempirical models shows that the temperature and intensity contrast are in broad agreement. However, the field strengths of the flux-tube models are somewhat lower than the values inferred from observations.

  3. 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.

  4. NUMERICAL EXPERIMENTS ON THE TWO-STEP EMERGENCE OF TWISTED MAGNETIC FLUX TUBES IN THE SUN

    SciTech Connect

    Toriumi, S.; Yokoyama, T.

    2011-07-10

    We present the new results of the two-dimensional numerical experiments on the cross-sectional evolution of a twisted magnetic flux tube rising from the deeper solar convection zone (-20,000 km) to the corona through the surface. The initial depth is 10 times deeper than most of the previous calculations focusing on the flux emergence from the uppermost convection zone. We find that the evolution is illustrated by the following two-step process. The initial tube rises due to its buoyancy, subject to aerodynamic drag due to the external flow. Because of the azimuthal component of the magnetic field, the tube maintains its coherency and does not deform to become a vortex roll pair. When the flux tube approaches the photosphere and expands sufficiently, the plasma on the rising tube accumulates to suppress the tube's emergence. Therefore, the flux decelerates and extends horizontally beneath the surface. This new finding owes to our large-scale simulation, which simultaneously calculates the dynamics within the interior as well as above the surface. As the magnetic pressure gradient increases around the surface, magnetic buoyancy instability is triggered locally and, as a result, the flux rises further into the solar corona. We also find that the deceleration occurs at a higher altitude than assumed in our previous experiment using magnetic flux sheets. By conducting parametric studies, we investigate the conditions for the two-step emergence of the rising flux tube: field strength {approx}> 1.5 x 10{sup 4} G and the twist {approx}> 5.0 x 10{sup -4} km{sup -1} at -20,000 km depth.

  5. Numerical simulations of magnetic Kelvin-Helmholtz instability at a twisted solar flux tube

    NASA Astrophysics Data System (ADS)

    Murawski, K.; Chmielewski, P.; Zaqarashvili, T. V.; Khomenko, E.

    2016-07-01

    The paper aims to study the response of a solar small-scale and weak magnetic flux tube to photospheric twisting motions. We numerically solve three-dimensional ideal magnetohydrodynamic equations to describe the evolution of the perturbation within the initially static flux tube, excited by twists in the azimuthal component of the velocity. These twists produce rotation of the magnetic field lines. Perturbation of magnetic field lines propagates upwardly, driving vertical and azimuthal flow as well as plasma compressions and rarefactions in the form of eddies. We conclude that these eddies result from the sheared azimuthal flow which seeds Kelvin-Helmholtz instability (KHI) between the flux tube and the ambient medium. Numerically obtained properties of the KHI confirm the analytical predictions for the occurrence of the instability.

  6. Axisymmetric and non-axisymmetric modulated MHD waves in magnetic flux tubes

    NASA Astrophysics Data System (ADS)

    Chargeishvili, B. B.; Japaridze, D. R.

    2016-02-01

    Nonlinear modulated both axisymmetric and non-axisymmetric MHD wave propagation in magnetic flux tubes is studied. In the cylindrical coordinates, ordinary differential equation with cubic nonlinearity is derived. In both cases of symmetry, the equation has solitary solutions. Modulation stability of the solutions is studied. The results of the study show that the propagation of axisymmetric soliton causes rising of plasma temperature in peripheral regions of a magnetic flux tube. In the non-axisymmetric case, it gives also temperature rising effect. Results of theoretical study are examined on idealized model of chromospheric spicule.

  7. Spectropolarimetric Evidence for a Siphon Flow along an Emerging Magnetic Flux Tube

    NASA Astrophysics Data System (ADS)

    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.

    2017-03-01

    We study the dynamics and topology of an emerging magnetic flux 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 magnetic 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 magnetic field is used to trace magnetic field lines. Two magnetic flux concentrations with different polarities and LOS velocities are found to be connected by a group of arch-shaped magnetic 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 magnetic flux tube.

  8. Numerical Simulations of Torsional Alfvén Waves in Axisymmetric Solar Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Wójcik, D.; Murawski, K.; Musielak, Z. E.; Konkol, P.; Mignone, A.

    2017-02-01

    We numerically investigate Alfvén waves propagating along an axisymmetric and non-isothermal solar flux tube embedded in the solar atmosphere. The tube magnetic field is current-free and diverges with height, and the waves are excited by a periodic driver along the tube magnetic field lines. The main results are that the two wave variables, the velocity and magnetic field perturbations in the azimuthal direction, behave differently as a result of gradients of the physical parameters along the tube. To explain these differences in the wave behavior, the time evolution of the wave variables and the resulting cutoff period for each wave variable are calculated and used to determine regions in the solar chromosphere where strong wave reflection may occur.

  9. The Role of Twisted Magnetic Flux Tubes in Topological Space Weather Forecasting

    NASA Astrophysics Data System (ADS)

    Nightingale, R. W.

    2008-12-01

    More and more twisted magnetic flux tubes are being identified in the solar active regions of solar cycle 23 utilizing imagery from high resolution satellite instrumentation, such as TRACE, Hinode, and SOHO/MDI. The twisted flux tubes carry energy and helicity via the Poynting Flux from below the photosphere up into the corona, where much of it is stored in the non-potentiality of the fields, many times visible in the form of sigmoidal and anti-sigmoidal shapes, until dissipation occurs mostly following eruptive events. The twisted flux tubes are easily observed and measured in TRACE whitelight in cross section as sunspots at the photosphere, which rotate about their umbral centers. The first results presented at the 2007 Fall AGU from a statistical study on the number of rotating sunspots showed that almost all of the measurable sunspots during the solar maximum year of 2000 were rotating. Here we extend the study to include halo coronal mass ejections (CMEs) observed by SOHO/LASCO, of which 80% are associated with rotating sunspots and twisted magnetic flux tubes in 2000. Many of the CMEs, consisting of very energetic particles normally captured within a magnetic cloud of twisted flux tubes, accelerate out into the heliosphere where the Earth and its magnetic fields can encounter them, causing large geomagnetic events, such as geomagnetic storms, Solar Particle Events (SPEs), and other space weather effects. The amount of twist, or helicity, and its directionality may play important roles in solar eruptions and in the CME's interaction with the magnetosphere. Within the next year the Solar Dynamics Observatory (SDO) will launch and the HMI and AIA instruments will be available to observe the rotating sunspots and twisted magnetic flux tubes in greater detail than is currently being done to improve our understanding of these processes. Examples of such events and topological features will be shown and discussed with respect to the role that twisted magnetic flux

  10. The stretching of magnetic flux tubes in the convective overshoot region

    NASA Technical Reports Server (NTRS)

    Fisher, George H.; Mcclymont, Alexander N.; Chou, Dean-Yi

    1991-01-01

    The present study examines the fate of a magnetic flux tube initially lying at the bottom of the solar convective overshoot region. Stretching of the flux tube, e.g., by differential rotation, reduces its density, causing it to rise quasi-statically (a process referred to as vertical flux drift) until it reaches the top of the overshoot region and enters the buoyantly unstable convection region, from which a portion of it may ultimately protrude to form an active region on the surface. It is suggested that vertical flux drift and flux destabilization are inevitable consequences of field amplification, and it is surmised that these phenomena should be considered in self-consistent models of solar and stellar dynamos operating in the overshoot region.

  11. Propagation of Long-Wavelength Nonlinear Slow Sausage Waves in Stratified Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Barbulescu, M.; Erdélyi, R.

    2016-05-01

    The propagation of nonlinear, long-wavelength, slow sausage waves in an expanding magnetic flux tube, embedded in a non-magnetic stratified environment, is discussed. The governing equation for surface waves, which is akin to the Leibovich-Roberts equation, is derived using the method of multiple scales. The solitary wave solution of the equation is obtained numerically. The results obtained are illustrative of a solitary wave whose properties are highly dependent on the degree of stratification.

  12. 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.

  13. Magnetic Reconnection in a Solar Eruption -Formation of the Flux Tube and its Eruption-

    NASA Astrophysics Data System (ADS)

    Inoue, Satoshi; Büchner, Jörg

    2016-07-01

    A solar eruption is one of a dramatic phenomenon observed in the solar corona. The flux tube, which is a bundle of highly twisted lines, is widely believed as a driver source of the eruption. Although the magnetic reconnection is a key process of the formation of the flux tube as well as the eruptive process, these dynamics are still open to be solved. In order to clarify these dynamics, we first perform a magnetohydrodynamic (MHD) simulation using a force-free field extrapolated from the photospheric magnetic field. Our simulation successfully produced the typical eruptive processes in which the twisted flux tube slowly ascends in the beginning of the eruption; afterwards, it shows the fast ascending. We found that the reconnection is a key process to break the force-free field initially constructed, and highly twisted flux tube formation during the slow rising phase and even after the fast eruption. Next we compare with Büchner + Skala simulations and compressively discuss the play of the reconnection in the solar eruption.

  14. Propagation and Dispersion of Sausage Wave Trains in Magnetic Flux Tubes

    NASA Astrophysics Data System (ADS)

    Oliver, R.; Ruderman, M. S.; Terradas, J.

    2015-06-01

    A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75-1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

  15. PROPAGATION AND DISPERSION OF SAUSAGE WAVE TRAINS IN MAGNETIC FLUX TUBES

    SciTech Connect

    Oliver, R.; Terradas, J.; Ruderman, M. S.

    2015-06-10

    A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75–1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

  16. Numerical simulation of filling a magnetic flux tube with a cold plasma: Anomalous plasma effects

    NASA Technical Reports Server (NTRS)

    Singh, Nagendra; Leung, W. C.

    1995-01-01

    Large-scale models of plasmaspheric refilling have revealed that during the early stage of the refilling counterstreaming ion beams are a common feature. However, the instability of such ion beams and its effect on refilling remain unexplored. In order to learn the basic effects of ion beam instabilities on refilling, we have performed numerical simulations of the refilling of an artificial magnetic flux tube. (The shape and size of the tube are assumed so that the essential features of the refilling problem are kept in the simulation and at the same time the small scale processes driven by the ion beams are sufficiently resolved.) We have also studied the effect of commonly found equatorially trapped warm and/or hot plasma on the filling of a flux tube with a cold plasma. Three types of simulation runs have been performed.

  17. Fast Solar Wind from Slowly Expanding Magnetic Flux Tubes (P54)

    NASA Astrophysics Data System (ADS)

    Srivastava, A. K.; Dwivedi, B. N.

    2006-11-01

    aks.astro.itbhu@gmail.com We present an empirical model of the fast solar wind, emanating from radially oriented slowly expanding magnetic flux tubes. We consider a single-fluid, steady state model in which the flow is driven by thermal and non-thermal pressure gradients. We apply a non-Alfvénic energy correction at the coronal base and find that specific relations correlate solar wind speed and non-thermal energy flux with the aerial expansion factor. The results are compared with the previously reported ones.

  18. FULLY RESOLVED QUIET-SUN MAGNETIC FLUX TUBE OBSERVED WITH THE SUNRISE/IMAX INSTRUMENT

    SciTech Connect

    Lagg, A.; Solanki, S. K.; Riethmueller, T. L.; Schuessler, M.; Hirzberger, J.; Feller, A.; Borrero, J. M.; Barthol, P.; Gandorfer, A.; MartInez Pillet, V.; Bonet, J. A.; Del Toro Iniesta, J. C.; Domingo, V.; Knoelker, M.; Title, A. M.

    2010-11-10

    Until today, the small size of magnetic elements in quiet-Sun areas has required the application of indirect methods, such as the line-ratio technique or multi-component inversions, to infer their physical properties. A consistent match to the observed Stokes profiles could only be obtained by introducing a magnetic filling factor that specifies the fraction of the observed pixel filled with magnetic field. Here, we investigate the properties of a small magnetic patch in the quiet Sun observed with the IMaX magnetograph on board the balloon-borne telescope SUNRISE with unprecedented spatial resolution and low instrumental stray light. We apply an inversion technique based on the numerical solution of the radiative transfer equation to retrieve the temperature stratification and the field strength in the magnetic patch. The observations can be well reproduced with a one-component, fully magnetized atmosphere with a field strength exceeding 1 kG and a significantly enhanced temperature in the mid to upper photosphere with respect to its surroundings, consistent with semi-empirical flux tube models for plage regions. We therefore conclude that, within the framework of a simple atmospheric model, the IMaX measurements resolve the observed quiet-Sun flux tube.

  19. Distortions of Magnetic Flux Tubes in the Presence of Electric Currents

    NASA Astrophysics Data System (ADS)

    Malanushenko, Anna; Rempel, Matthias; Cheung, Mark

    2016-05-01

    Solar coronal loops possess several peculiar properties, which have been a subject of intensive research for a long time. These in particular include the lack of apparent expansion of coronal loops and the increased pressure scale height in loops compared to the diffuse background. Previously, Malanushenko & Schrijver (2013) proposed that these could be explained by the fact that magnetic flux tubes expand with height in a highly anisotropic manner. They used potential field models to demonstrate that flux tubes that have circular cross section at the photosphere, in the corona turn into a highly elongates structures, more resembling thick ribbons. Such ribbons, viewed along the expanding edge, would appear as thin, crisp structures of a constant cross-section with an increased pressure scale height, and when viewed along the non-expanding side, would appear as faint, wide and underdense features. This may also introduce a selection bias,when a set of loops is collected for a further study, towards those viewed along the expanding edge.However, some of the past studies have indicated that strong electric currents flowing in a given flux tube may result in the tube maintaining a relatively constant cross-sectional shape along its length. Given that Malanushenko & Schrijver (2013) focused on a potential, or current-free, field model of an active region, the extend to which their analysis could be applied to the real solar fields, was unclear.In the present study, we use a magnetic field created by MURaM, a highly realistic state-of-the-art radiative MHD code (Vogler et al, 2005; Rempel et al, 2009b). MURaM was shown to reproduce a wide variety of observed features of the solar corona (e.g., Hansteen et al, 2010; Cheung et al. 2007, 2008; Rempel 2009a,b). We analyze the distortions of magnetic flux tubes in a MURaM simulation of an active region corona. We quantify such distortions and correlate them with a number of relevant parameters of flux tubes, with a

  20. KELVIN-HELMHOLTZ INSTABILITY IN CORONAL MAGNETIC FLUX TUBES DUE TO AZIMUTHAL SHEAR FLOWS

    SciTech Connect

    Soler, R.; Terradas, J.; Oliver, R.; Ballester, J. L.; Goossens, M.

    2010-04-01

    Transverse oscillations of coronal loops are often observed and have been theoretically interpreted as kink magnetohydrodynamic (MHD) modes. Numerical simulations by Terradas et al. suggest that shear flows generated at the loop boundary during kink oscillations could give rise to a Kelvin-Helmholtz instability (KHI). Here, we investigate the linear stage of the KHI in a cylindrical magnetic flux tube in the presence of azimuthal shear motions. We consider the basic, linearized MHD equations in the beta = 0 approximation and apply them to a straight and homogeneous cylindrical flux tube model embedded in a coronal environment. Azimuthal shear flows with a sharp jump of the velocity at the cylinder boundary are included in the model. We obtain an analytical expression for the dispersion relation of the unstable MHD modes supported by the configuration, and compute analytical approximations of the critical velocity shear and the KHI growth rate in the thin tube limit. A parametric study of the KHI growth rates is performed by numerically solving the full dispersion relation. We find that fluting-like modes can develop a KHI in timescales comparable to the period of kink oscillations of the flux tube. The KHI growth rates increase with the value of the azimuthal wavenumber and decrease with the longitudinal wavenumber. However, the presence of a small azimuthal component of the magnetic field can suppress the KHI. Azimuthal motions related to kink oscillations of untwisted coronal loops may trigger a KHI, but this phenomenon has not been observed to date. We propose that the azimuthal component of the magnetic field is responsible for suppressing the KHI in a stable coronal loop. The required twist is small enough to prevent the development of the pinch instability.

  1. Peculiarities of Alfven wave propagation along a nonuniform magnetic flux tube

    SciTech Connect

    Erkaev, N.V.; Shaidurov, V.A.; Semenov, V.S.; Langmayr, D.; Biernat, H.K.

    2005-01-01

    Within the framework of the assumption of large azimuthal wave numbers, the equations for Alfven and slow magnetosonic waves are obtained using frozen-in material coordinates. These equations are specified for the case of a nonuniform magnetic field with axial symmetry. Assuming a meridional polarization of the magnetic field and velocity perturbations, the effects of Alfven wave propagation are analyzed which are related to geometric characteristics of a nonuniform magnetic field: (a) A finite curvature radius of the magnetic field lines and (b) convergence of magnetic field lines. The interaction between the Alfven and magnetosonic waves is found to be strongly dependent on the curvature radius of the magnetic tube and the local plasma {beta} parameter. The electric field amplitude and the length scale of a wave front are found to increase very strongly in the course of the Alfven wave propagation along a converging magnetic flux tube. Also studied is a temporal decrease of the wave perturbations which is caused by dissipation at the conducting boundary.

  2. First Reconnected Flux Tubes

    NASA Astrophysics Data System (ADS)

    Andersson, L.; Lapenta, G.; Newman, D. L.; Markidis, S.; Spanswick, E. L.; Baker, J. B.; Clausen, L. B.; Larson, D. E.; Ergun, R. E.; Frey, H. U.; Singer, H. J.; Angelopoulos, V.; Bonnell, J. W.; McFadden, J. P.; Glassmeier, K.; Wolfgang, B.

    2011-12-01

    THEMIS observations from the magnetic equator (the equatorial plane) in the near-earth tail reveal a great amount of information regarding the plasma environment in the vicinity of the first reconnected flux tubes (a subgroup of dipolarization fronts). Two sequential observations of dipolarization fronts are analyzed in detail using three of the THEMIS spacecraft. Particle acceleration to high energies (>50 keV) is observed together with a void region interpreted as a region to which the full electron distribution has incomplete access. Whistler waves, which are observed, could be driven by one of the two electron populations located in the wake of the first reconnected flux tubes. The detailed observations are compared with 2D and 3D implicit kinetic simulation of reconnection events. This presentation focuses on the similarity between observation and simulation. One key aspect of this presentation is a demonstration of how different the signature is when observing at vs off the magnetic equator, since most observations in the literature (unlike the observations presented here) are from off the equator. For this event, additional spacecraft and ground observations have been analyzed, which demonstrate that a reconfiguration of the magnetosphere is taking place. However, the focus of this presentation is on the small scale (<~10 di), rather than the large scale (~20 Re).

  3. The dynamic evolution of active-region-scale magnetic flux tubes in the turbulent solar convective envelope

    NASA Astrophysics Data System (ADS)

    Weber, Maria Ann

    2014-12-01

    The Sun exhibits cyclic properties of its large-scale magnetic field on the order of sigma22 years, with a ˜11 year frequency of sunspot occurrence. These sunspots, or active regions, are the centers of magnetically driven phenomena such as flares and coronal mass ejections. Volatile solar magnetic events directed toward the Earth pose a threat to human activities and our increasingly technological society. As such, the origin and nature of solar magnetic flux emergence is a topic of global concern. Sunspots are observable manifestations of solar magnetic fields, thus providing a photospheric link to the deep-seated dynamo mechanism. However, the manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. The convective velocity field interacts with the flux tube through the drag force it experiences as it traverses through the convecting medium. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective

  4. Observations on Characterization of Defects in Coiled Tubing From Magnetic-Flux-Leakage Data

    SciTech Connect

    Timothy R. McJunkin; Karen S. Miller; Charles R. Tolle

    2006-04-01

    This paper presents observations on the sizing of automatically detected artificial flaws in coiled tubing samples using magnetic-flux-leakage data. Sixty-six artificial flaws of various shapes and types, ranging from 0.30 mm deep pits to slots with length of 9.5 mm, in 44.45 mm outer diameter pipe were analyzed. The detection algorithm and the information automatically extracted from the data are described. Observations on the capabilities and limitations for determining the size and shape of the flaws are discussed.

  5. The motion of magnetic flux tube at the dayside magnetopause under the influence of solar wind flow

    SciTech Connect

    Liu, Z.X.; Hu, Y.D.; Li, F. ); Pu, Z.Y. )

    1990-05-01

    The authors propose that flux transfer events (FTEs) at the dayside magnetopause are formed by fluid vortices in the flow field. According to the view of vortex-induced reconnection a FTE tube is a magnetic fluid vortex tube (MF vortex tube). The motion of a FTE tube can be represented by that of a MF vortex in the formation region located in the dayside magnetopause region. This study deals with the internal and external influences governing the motion of MF vortex tubes. The equations of motion of a vortex tube are established and solved. It is found that a FTE tube moves frm low latitude to high latitude with a certain speed. However, the motional path is not a straight line but oscillates about the northward direction for the northern hemisphere. The motional velocity, amplitude and period of the oscillation depend on the flow field and magnetic field in the magnetosheath and magnetosphere as well as the size of the FTE tube.

  6. Propagation and dispersion of transverse wave trains in magnetic flux tubes

    SciTech Connect

    Oliver, R.; Terradas, J.; Ruderman, M. S.

    2014-07-01

    The dispersion of small-amplitude, impulsively excited wave trains propagating along a magnetic flux tube is investigated. The initial disturbance is a localized transverse displacement of the tube that excites a fast kink wave packet. The spatial and temporal evolution of the perturbed variables (density, plasma displacement, velocity, ...) is given by an analytical expression containing an integral that is computed numerically. We find that the dispersion of fast kink wave trains is more important for shorter initial disturbances (i.e., more concentrated in the longitudinal direction) and for larger density ratios (i.e., for larger contrasts of the tube density with respect to the environment density). This type of excitation generates a wave train whose signature at a fixed position along a coronal loop is a short event (duration ≅ 20 s) in which the velocity and density oscillate very rapidly with typical periods of the order of a few seconds. The oscillatory period is not constant but gradually declines during the course of this event. Peak values of the velocity are of the order of 10 km s{sup –1} and are accompanied by maximum density variations of the order of 10%-15% the unperturbed loop density.

  7. Structural properties of the solar flare-producing coronal current system developed in an emerging magnetic flux tube

    NASA Astrophysics Data System (ADS)

    Magara, Tetsuya

    2017-02-01

    The activity of a magnetic structure formed in the solar corona depends on a coronal current system developed in the structure, which determines how an electric current flows in the corona. To investigate structural properties of the coronal current system responsible for producing a solar flare, we perform magnetohydrodynamic simulation of an emerging magnetic flux tube which forms a coronal magnetic structure. Investigation using fractal dimensional analysis and electric current streamlines reveals that the flare-producing coronal current system relies on a specific coronal current structure of two-dimensional spatiality, which has a sub-region where a nearly anti-parallel magnetic field configuration is spontaneously generated. We discuss the role of this locally generated anti-parallel magnetic field configuration in causing the reconnection of a three-dimensional magnetic field, which is a possible mechanism for producing a flare. We also discuss how the twist of a magnetic flux tube affects structural properties of a coronal current system, showing how much volume current flux is carried into the corona by an emerging flux tube. This gives a way to evaluate the activity of a coronal magnetic structure.

  8. Magnetic-flux-driven topological quantum phase transition and manipulation of perfect edge states in graphene tube

    PubMed Central

    Lin, S.; Zhang, G.; Li, C.; Song, Z.

    2016-01-01

    We study the tight-binding model for a graphene tube with perimeter N threaded by a magnetic field. We show exactly that this model has different nontrivial topological phases as the flux changes. The winding number, as an indicator of topological quantum phase transition (QPT) fixes at N/3 if N/3 equals to its integer part [N/3], otherwise it jumps between [N/3] and [N/3] + 1 periodically as the flux varies a flux quantum. For an open tube with zigzag boundary condition, exact edge states are obtained. There exist two perfect midgap edge states, in which the particle is completely located at the boundary, even for a tube with finite length. The threading flux can be employed to control the quantum states: transferring the perfect edge state from one end to the other, or generating maximal entanglement between them. PMID:27554930

  9. Magnetic-flux-driven topological quantum phase transition and manipulation of perfect edge states in graphene tube.

    PubMed

    Lin, S; Zhang, G; Li, C; Song, Z

    2016-08-24

    We study the tight-binding model for a graphene tube with perimeter N threaded by a magnetic field. We show exactly that this model has different nontrivial topological phases as the flux changes. The winding number, as an indicator of topological quantum phase transition (QPT) fixes at N/3 if N/3 equals to its integer part [N/3], otherwise it jumps between [N/3] and [N/3] + 1 periodically as the flux varies a flux quantum. For an open tube with zigzag boundary condition, exact edge states are obtained. There exist two perfect midgap edge states, in which the particle is completely located at the boundary, even for a tube with finite length. The threading flux can be employed to control the quantum states: transferring the perfect edge state from one end to the other, or generating maximal entanglement between them.

  10. On the area expansion of magnetic flux tubes in solar active regions

    SciTech Connect

    Dudík, Jaroslav; Dzifčáková, Elena; Cirtain, Jonathan W. E-mail: elena@asu.cas.cz

    2014-11-20

    We calculated the three-dimensional (3D) distribution of the area expansion factors in a potential magnetic 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 distribution 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 flux tubes have squashed cross-sections and expand with height. The distribution 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 flux distribution in the observed magnetogram, but removes the small-scale structure in both the approximated magnetogram and the 3D distribution 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.

  11. Flux Tube Model

    NASA Astrophysics Data System (ADS)

    Steiner, O.

    2011-05-01

    This Fortran code computes magnetohydrostatic flux tubes and sheets according to the method of Steiner, Pneuman, & Stenflo (1986) A&A 170, 126-137. The code has many parameters contained in one input file that are easily modified. Extensive documentation is provided in README files.

  12. The Scattering of f- and p-modes from Ensembles of Thin Magnetic Flux Tubes: An Analytical Approach

    NASA Astrophysics Data System (ADS)

    Hanson, Chris S.; Cally, Paul S.

    2014-08-01

    Motivated by the observational results of Braun, we extend the model of Hanson & Cally to address the effect of multiple scattering of f and p modes by an ensemble of thin vertical magnetic flux tubes in the surface layers of the Sun. As in the observational Hankel analysis, we measure the scatter and phase shift from an incident cylindrical wave in a coordinate system roughly centered in the core of the ensemble. It is demonstrated that although thin flux tubes are unable to interact with high-order fluting modes individually, they can indirectly absorb energy from these waves through the scatters of kink and sausage components. It is also shown how the distribution of absorption and phase shift across the azimuthal order m depends strongly on the tube position as well as on the individual tube characteristics. This is the first analytical study into an ensembles multiple-scattering regime that is embedded within a stratified atmosphere.

  13. Investigating the Dynamics of Canonical Flux Tubes

    NASA Astrophysics Data System (ADS)

    von der Linden, Jens; Sears, Jason; Intrator, Thomas; You, Setthivoine

    2016-10-01

    Canonical flux tubes are flux tubes of the circulation of a species' canonical momentum. They provide a convenient generalization of magnetic flux tubes to regimes beyond magnetohydrodynamics (MHD). We hypothesize that hierarchies of instabilities which couple disparate scales could transfer magnetic pitch into helical flows and vice versa while conserving the total canonical helicity. This work first explores the possibility of a sausage instability existing on top of a kink as mechanism for coupling scales, then presents the evolution of canonical helicity in a gyrating kinked flux rope. Analytical and numerical stability spaces derived for magnetic flux tubes with core and skin currents indicate that, as a flux tube lengthens and collimates, it may become kink unstable with a sausage instability developing on top of the kink. A new analysis of 3D magnetic field and ion flow data on gyrating kinked magnetic flux ropes from the Reconnection Scaling Experiment tracks the evolution of canonical flux tubes and their helicity. These results and methodology are being developed as part of the Mochi experiment specifically designed to observe the dynamics of canonical flux tubes. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-697161.

  14. Dynamics of flux tubes in accretion disks

    NASA Technical Reports Server (NTRS)

    Vishniac, E. T.; Duncan, R. C.

    1994-01-01

    The study of magnetized plasmas in astrophysics is complicated by a number of factors, not the least of which is that in considering magnetic fields in stars or accretion disks, we are considering plasmas with densities well above those we can study in the laboratory. In particular, whereas laboratory plasmas are dominated by the confining magnetic field pressure, stars, and probably accretion disks, have magnetic fields whose beta (ratio of gas pressure to magnetic field pressure) is much greater than 1. Observations of the Sun suggest that under such circumstances the magnetic field breaks apart into discrete flux tubes with a small filling factor. On the other hand, theoretical treatments of MHD turbulence in high-beta plasmas tend to assume that the field is more or less homogeneously distributed throughout the plasma. Here we consider a simple model for the distribution of magnetic flux tubes in a turbulent medium. We discuss the mechanism by which small inhomogeneities evolve into discrete flux tubes and the size and distribution of such flux tubes. We then apply the model to accretion disks. We find that the fibrilation of the magnetic field does not enhance magnetic buoyancy. We also note that the evolution of an initially diffuse field in a turbulent medium, e.g., any uniform field in a shearing flow, will initially show exponential growth as the flux tubes form. This growth saturates when the flux tube formation is complete and cannot be used as the basis for a self-sustaining dynamo effect. Since the typical state of the magnetic field is a collection of intense flux tubes, this effect is of limited interest. However, it may be important early in the evolution of the galactic magnetic field, and it will play a large role in numerical simulations. Finally, we note that the formation of flux tubes is an essential ingredient in any successful dynamo model for stars or accretion disks.

  15. The Topology of Canonical Flux Tubes in Flared Jet Geometry

    NASA Astrophysics Data System (ADS)

    Sander Lavine, Eric; You, Setthivoine

    2017-01-01

    Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). We outline here a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of the species’ canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. A flared, current-carrying magnetic flux tube in an ion-electron plasma with finite ion momentum is thus equivalent to either a pair of electron and ion flow flux tubes, a pair of electron and ion canonical momentum flux tubes, or a pair of electron and ion canonical vorticity flux tubes. We examine the morphology of all these flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, axisymmetric magnetic geometry. Calculations of gauge-invariant relative canonical helicities track the evolution of magnetic, cross, and kinetic helicities in the system, and show that ion flow fields can unwind to compensate for an increasing magnetic twist. The results demonstrate that including a species’ finite momentum can result in a very long collimated canonical vorticity flux tube even if the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities, not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes.

  16. On magnetohydrodynamic thermal instabilities in magnetic flux tubes. [in plane parallel stellar atmosphere in LTE and hydrostatic equilibrium

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    The stability of current-driven filamentary modes in magnetic flux tubes embedded in a plane-parallel atmosphere in LTE and in hydrostatic equilibrium is discussed. Within the tube, energy transport by radiation only is considered. The dominant contribution to the opacity is due to H- ions and H atoms (in the Paschen continuum). A region in the parameter space of the equilibrium configuration in which the instability is effective is delimited, and the relevance of this process for the formation of structured coronae in late-type stars and accretion disks is discussed.

  17. Evolution of a magnetic flux tube in two-dimensional penetrative convection

    NASA Technical Reports Server (NTRS)

    Jennings, R. L.; Brandenburg, A.; Nordlund, A.; Stein, R. F.

    1992-01-01

    Highly supercritical compressible convection is simulated in a two-dimensional domain in which the upper half is unstable to convection while the lower half is stably stratified. This configuration is an idealization of the layers near the base of the solar convection zone. Once the turbulent flow is well developed, a toroidal magnetic field B sub tor is introduced to the stable layer. The field's evolution is governed by an advection-diffusion-type equation, and the Lorentz force does not significantly affect the flow. After many turnover times the field is stratified such that the absolute value of B sub tor/rho is approximately constant in the convective layer, where rho is density, while in the stable layer this ratio decreases linearly with depth. Consequently most of the magnetic flux is stored in the overshoot layer. The inclusion of rotation leads to travelling waves which transport magnetic flux latitudinally in a manner reminiscent of the migrations seen during the solar cycle.

  18. Charm production in flux tubes

    NASA Astrophysics Data System (ADS)

    Aguiar, C. E.; Kodama, T.; Nazareth, R. A. M. S.; Pech, G.

    1996-01-01

    We argue that the nonperturbative Schwinger mechanism may play an important role in the hadronic production of charm. We present a flux tube model which assumes that the colliding hadrons become color charged because of gluon exchange, and that a single nonelementary flux tube is built up as they recede. The strong chromoelectric field inside this tube creates quark pairs (including charmed ones) and the ensuing color screening breaks the tube into excited hadronic clusters. In their turn these clusters, or ``fireballs,'' decay statistically into the final hadrons. The model is able to account for the soft production of charmed, strange, and lighter hadrons within a unified framework.

  19. Diamagnetic force on a flux tube

    NASA Technical Reports Server (NTRS)

    Yeh, T.

    1983-01-01

    The diamagnetic force on a straight flux tube is elucidated. The case when the flux tube has a circular cross section is considered, and the result is generalized to the case of noncircular cross section. The result shows that when the external magnetic field is uniform, the diamagnetic force is simply equal to the vector multiplication of the internal conduction current and the external magnetic field. It is independent of the size and shape of the cross section of the flux tube. This is analogous to the Kutta-Joukowski theorem that the aerodynamic lift force is proportional to the vector multiplication of the unperturbed flow velocity and the circulation around the airfoil. When the external magnetic field is nonuniform, the diamagnetic force has an additional contribution which is proportional to the gradient of magnetic pressure and to the volume of the flux tube. The constant of proportionality, which is shown to be equal to two for a circular cross section, indicates the enhancement of the nonuniformity of the external magnetic field in the vicinity of the periphery by the polarization current.

  20. Self-organized criticality in a two-dimensional cellular automaton model of a magnetic flux tube with background flow

    NASA Astrophysics Data System (ADS)

    Dănilă, B.; Harko, T.; Mocanu, G.

    2015-11-01

    We investigate the transition to self-organized criticality in a two-dimensional model of a flux tube with a background flow. The magnetic induction equation, represented by a partial differential equation with a stochastic source term, is discretized and implemented on a two-dimensional cellular automaton. The energy released by the automaton during one relaxation event is the magnetic energy. As a result of the simulations, we obtain the time evolution of the energy release, of the system control parameter, of the event lifetime distribution and of the event size distribution, respectively, and we establish that a self-organized critical state is indeed reached by the system. Moreover, energetic initial impulses in the magnetohydrodynamic flow can lead to one-dimensional signatures in the magnetic two-dimensional system, once the self-organized critical regime is established. The applications of the model for the study of gamma-ray bursts (GRBs) is briefly considered, and it is shown that some astrophysical parameters of the bursts, like the light curves, the maximum released energy and the number of peaks in the light curve can be reproduced and explained, at least on a qualitative level, by working in a framework in which the systems settles in a self-organized critical state via magnetic reconnection processes in the magnetized GRB fireball.

  1. The Topology of Canonical Flux Tubes in Flared Jet Geometry

    NASA Astrophysics Data System (ADS)

    Lavine, Eric Sander; You, Setthivoine

    2016-10-01

    Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by MHD. We outline here a more fundamental approach based on flux tubes of canonical vorticity. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. We examine the morphology of these canonical flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, dipole magnetic field. Calculations of gauge-invariant relative canonical helicity track the evolution of magnetic, cross, and kinetic helicities in the system and show that ion flow fields can unwind to compensate for increasing magnetic twist. The results demonstrate that including a species' finite momentum can result in long, collimated canonical vorticity flux tubes even when the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes. This work is supported by DOE Grant DE-SC0010340.

  2. 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.

  3. 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.

  4. Resonant behaviour of MHD waves on magnetic flux tubes. III - Effect of equilibrium flow

    NASA Technical Reports Server (NTRS)

    Goossens, Marcel; Hollweg, Joseph V.; Sakurai, Takashi

    1992-01-01

    The Hollweg et al. (1990) analysis of MHD surface waves in a stationary equilibrium is extended. The conservation laws and jump conditions at Alfven and slow resonance points obtained by Sakurai et al. (1990) are generalized to include an equilibrium flow, and the assumption that the Eulerian perturbation of total pressure is constant is recovered as the special case of the conservation law for an equilibrium with straight magnetic field lines and flow along the magnetic field lines. It is shown that the conclusions formulated by Hollweg et al. are still valid for the straight cylindrical case. The effect of curvature is examined.

  5. Laboratory Experiment of Magnetic Reconnection between Merging Flux Tubes with Strong Guide FIeld

    NASA Astrophysics Data System (ADS)

    Inomoto, M.; Kamio, S.; Kuwahata, A.; Ono, Y.

    2013-12-01

    Magnetic reconnection governs variety of energy release events in the universe, such as solar flares, geomagnetic substorms, and sawtooth crash in laboratory nuclear fusion experiments. Differently from the classical steady reconnection models, non-steady behavior of magnetic reconnection is often observed. In solar flares, intermittent enhancement of HXR emission is observed synchronously with multiple ejection of plammoids [1]. In laboratory reconnection experiments, the existence of the guide field, that is perpendicular to the reconnection field, makes significant changes on reconnection process. Generally the guide field will slow down the reconnection rate due to the increased magnetic pressure inside the current sheet. It also brings about asymmetric structure of the separatrices or effective particle acceleration in collisionless conditions. We have conducted laboratory experiments to study the behavior of the guide-field magnetic reconnection using plasma merging technique (push reconnection). Under substantial guide field even larger than the reconnection field, the reconnection generally exhibits non-steady feature which involves intermittent detachment of X-point and reconnection current center[2]. Transient enhancement of reconnection rate is observed simultaneously with the X-point motion[3]. We found two distinct phenomena associated with the guide-field non-steady reconnection. The one is the temporal and localized He II emission from X-point region, suggesting the production of energetic electrons which could excite the He ions in the vicinity of the X-point. The other is the excitation of large-amplitude electromagnetic waves which have similar properties with kinetic Alfven waves, whose amplitude show positive correlation with the enhancement of the reconnection electric field[4]. Electron beam instability caused by the energetic electrons accelerated to more than twice of the electron thermal velocity could be a potential driver of the

  6. Dynamic phenomena in coronal flux tubes

    NASA Technical Reports Server (NTRS)

    Mariska, J. T.; Boris, J. P.

    1981-01-01

    The study of stellar atmospheres and the determination of specific physical mechanisms, geometries, and magnetic structures by which coronae are maintained is examined. Ultraviolet and soft X-ray components observed in the radiative output of cool stars and the Sun require counterentropic temperature gradients for their explanation. The existence of a hot corona is recognized as a result of mechanical or fluid dynamic effects and the importance of the magnetic field in the heating is accepted. Magnetohydrodynamic energy release associated with the emergence of magnetic flux through the chromosphere and its dynamic readjustment in the corona are major counterentropic phenomena which are considered as primary candidates for corona heating. Systematic plows in coronal flux tubes result from asymmetric heating and systematic flows can exist without substantial chromospheric pressure differences.

  7. Interaction of twisted curved flux tubes

    NASA Astrophysics Data System (ADS)

    Selwa, Malgorzata; Parnell, Clare; Priest, Eric

    Most solar eruptions are initiated from sigmoidal structures. We perform 3D MHD numerical experiments of the interaction of force-free dipolar flux tubes. The magnetic configuration is initialized as either a potential or a force-free dipole with a constant density. Next we perturb the dipoles by twisting or rotating them leading to reconnection in a resistive MHD regime. We compare the connectivity, energetics and topological features in both models, vary the contact angle of the dipoles and check if the initial configuration (sigmoidal or not) affects flares and eruption initiation leading to faster and stronger reconnection.

  8. Benchmarking gyrokinetic simulations in a toroidal flux-tube

    SciTech Connect

    Chen, Y.; Parker, S. E.; Wan, W.; Bravenec, R.

    2013-09-15

    A flux-tube model is implemented in the global turbulence code GEM [Y. Chen and S. E. Parker, J. Comput. Phys. 220, 839 (2007)] in order to facilitate benchmarking with Eulerian codes. The global GEM assumes the magnetic equilibrium to be completely given. The initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, etc.) to be equal to the values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. This implementation shows disagreement with Eulerian codes in linear simulations. An alternative flux-tube model based on a complete local equilibrium solution of the Grad-Shafranov equation [J. Candy, Plasma Phys. Controlled Fusion 51, 105009 (2009)] is then implemented. This results in better agreement between Eulerian codes and the particle-in-cell (PIC) method. The PIC algorithm based on the v{sub ||}-formalism [J. Reynders, Ph.D. dissertation, Princeton University, 1992] and the gyrokinetic ion/fluid electron hybrid model with kinetic electron closure [Y. Chan and S. E. Parker, Phys. Plasmas 18, 055703 (2011)] are also implemented in the flux-tube geometry and compared with the direct method for both the ion temperature gradient driven modes and the kinetic ballooning modes.

  9. 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.

  10. Dissipationless Damping of Compressive MHD Modes in Twisted Flux Tubes

    NASA Astrophysics Data System (ADS)

    Giagkiozis, I.; Fedun, V.; Verth, G.; Goossens, M. L.; Van Doorsselaere, T.

    2015-12-01

    Axisymmetric modes in straight magentic flux tubes exhibit a cutoff in the long wavelength limit and no damping is predicted. However, as soon as weak magnetic twist is introduced inside as well as outside the magnetic flux tube the cutoff recedes. Furthermore, when density variations are also incomporated within the modelresonant absorption appears. In this work we explore analytically the expected damping times for waves within the Alfven continuum for different solar atmospheric conditions. Based on the results in this work we offer insight on recent observations of sausage wave damping in the chromosphere.

  11. Monte Carlo simulation of false alarms and detection reliability in magnetic flux leakage inspection of steel tubes

    SciTech Connect

    Altschuler, E.; Pignotti, A.; Paiuk, J.

    1996-09-01

    The same flaw gives rise to different signals when inspected by the same nondestructive testing (NDT) equipment under closely similar circumstances. A laboratory example involving six identical cracks is shown. This is a consequence of unavoidable fluctuations in the parameters that influence the detection process and is illustrated using a Monte Carlo simulation based on a numerical model of crack detection in steel pipes by magnetic flux leakage. The effects of these uncertainties on the fault detection reliability and on the appearance of false alarms are analyzed. The occurrence of Type I errors (lack of detection of unacceptable defects) and Type II errors (false alarms) is studied as a function of the detection threshold, and guidelines for improving detection efficiency are suggested.

  12. Effective string description of confining flux tubes

    NASA Astrophysics Data System (ADS)

    Brandt, Bastian B.; Meineri, Marco

    2016-08-01

    We review the current knowledge about the theoretical foundations of the effective string theory for confining flux tubes and the comparison of the predictions to pure gauge lattice data. A concise presentation of the effective string theory is provided, incorporating recent developments. We summarize the predictions for the spectrum and the profile/width of the flux tube and their comparison to lattice data. The review closes with a short summary of open questions for future research.

  13. Flux tube analysis of L-band ionospheric scintillation

    NASA Astrophysics Data System (ADS)

    Shume, E. B.; Mannucci, A. J.; Butala, M. D.; Pi, X.; Valladares, C. E.

    2013-06-01

    This manuscript presents magnetic flux tube analysis of L-band signal scintillation in the nighttime equatorial and low-latitude ionosphere. Residues of the scintillation index S4 estimated from the L-band signals received from Geostationary Earth Orbit (GEO) satellites are employed in the analysis. The S4 estimates have been shown to be associated with simultaneous GPS VTEC variations derived from JPL's GIPSY-GIM package. We have applied the wavelet decomposition technique simultaneously on the S4 time series in a flux tube over the equatorial and low-latitude regions. The technique decomposes the S4 signal to identify the dominant mode of variabilities and the temporal variations of scintillation-producing irregularities in the context of a flux tube. Statistically significant regions of the wavelet power spectra considered in our study have mainly shown that (a) dominant plasma irregularities associated with S4 variabilities in a flux tube have periods of about 4 to 15 minutes (horizontal irregularity scales of about 24 to 90 km). These periods match short period gravity waves, (b) scintillation-producing irregularities are anisotropic along the flux tube and in the east-west direction, and (c) the occurrences of scintillation-producing irregularities along the flux tube indicate that the entire flux tube became unstable. However, plasma instability occurrences were not simultaneous in most cases along the flux tube, there were time delays of various orders. Understanding the attributes of L-band scintillation-producing irregularities could be important for developing measures to mitigate L-band signal degradation.

  14. Evidence of Twisted Flux-Tube Emergence in Active Regions

    NASA Astrophysics Data System (ADS)

    Poisson, M.; Mandrini, C. H.; Démoulin, P.; López Fuentes, M.

    2015-03-01

    Elongated magnetic polarities are observed during the emergence phase of bipolar active regions (ARs). These extended features, called magnetic tongues, are interpreted as a consequence of the azimuthal component of the magnetic flux in the toroidal flux-tubes that form ARs. We develop a new systematic and user-independent method to identify AR tongues. Our method is based on determining and analyzing the evolution of the AR main polarity inversion line (PIL). The effect of the tongues is quantified by measuring the acute angle [ τ] between the orientation of the PIL and the direction orthogonal to the AR main bipolar axis. We apply a simple model to simulate the emergence of a bipolar AR. This model lets us interpret the effect of magnetic tongues on parameters that characterize ARs ( e.g. the PIL inclination and the tilt angles, and their evolution). In this idealized kinematic emergence model, τ is a monotonically increasing function of the twist and has the same sign as the magnetic helicity. We systematically apply our procedure to a set of bipolar ARs (41 ARs) that were observed emerging in line-of-sight magnetograms over eight years. For most of the cases studied, the tongues only have a small influence on the AR tilt angle since tongues have a much lower magnetic flux than the more concentrated main polarities. From the observed evolution of τ, corrected for the temporal evolution of the tilt angle and its final value when the AR is fully emerged, we estimate the average number of turns in the subphotospherically emerging flux-rope. These values for the 41 observed ARs are below unity, except for one. This indicates that subphotospheric flux-ropes typically have a low amount of twist, i.e. highly twisted flux-tubes are rare. Our results demonstrate that the evolution of the PIL is a robust indicator of the presence of tongues and constrains the amount of twist in emerging flux-tubes.

  15. 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):

  16. Empty Flux Tubes and Plasmasphere Refilling as Seen by IMAGE

    NASA Technical Reports Server (NTRS)

    Adrian, M. L.; Gallagher, D. L.; Sandel, B. R.; Green, J. L.; Reinish, B.; Goldstein, J.; Huegrich, T.

    2002-01-01

    When a plasmaspheric flux tube is empty, what plasma is actually missing? When a flux tube refills, where does the plasma accumulate first? How long does it take to refill a flux tube to a level that is essentially saturated? Owing to the observational difficulties of measuring the distribution of plasmaspheric plasma along a flux tube, these questions have remained unanswered over many decades of study since discovery of the plasmasphere. They are important questions, because of the role that plasmaspheric plasma plays in collisional losses of higher energy populations, in modifying instabilities for wave-particle interactions, and in influencing the transport of energy through plasma waves. The Extreme Ultraviolet Imager and the Radio Plasma Imager on the IMAGE Mission are providing new, critical observations of the dynamic outer plasmasphere where convective erosion and refilling dominate. Latitudinal density profiles along a single L-shell from BPI confirm earlier indications of a mid-latitude transition between the altitude organized structure of the ionosphere and L-shell organized plasmasphere. Emptied flux tubes often mean empty only above about 1 Re in altitude or below plus or minus 40 degrees in magnetic latitude. Refilling to nearly saturated levels is found to take much less than that previously found necessary to complete the process. The observations behind these conclusions and the new light brought to plasmaspheric refilling will be discussed.

  17. High-energy X-Ray Detection of G359.89-0.08 (Sgr A-E): Magnetic Flux Tube Emission Powered by Cosmic Rays?

    NASA Astrophysics Data System (ADS)

    Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A.; Zhang, William W.

    2014-03-01

    We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ~50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is FX = (2.0 ± 0.1) × 10-12 erg cm-2 s-1, corresponding to an unabsorbed X-ray luminosity LX = (2.6 ± 0.8) × 1034 erg s-1 assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A-E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ~100 kyr) with low surface brightness and radii up to ~30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  18. High-Energy X-Ray Detection of G359.89-0.08 (SGR A-E): Magnetic Flux Tube Emission Powered by Cosmic Rays?

    NASA Technical Reports Server (NTRS)

    Zhang, Shuo; Hailey, Charles J.; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Christensen, Finn E.; Gotthelf, Eric V.; Harrison, Fiona A.; Mori, Kaya; Nynka, Melania; Stern, Daniel; Tomsick, John A; Zhang, Will

    2014-01-01

    We report the first detection of high-energy X-ray (E (is) greater than 10 keV) emission from the Galactic center non-thermal filament G359.89-0.08 (Sgr A-E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to approximately 50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index gamma approximately equals 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F(sub X) = (2.0 +/- 0.1) × 10(exp -12)erg cm(-2) s(-1) , corresponding to an unabsorbed X-ray luminosity L(sub X) = (2.6+/-0.8)×10(exp 34) erg s(-1) assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A-E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to (is) approximately 100 kyr) with low surface brightness and radii up to (is) approximately 30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  19. Supersymmetric quantum mechanics of the flux tube

    NASA Astrophysics Data System (ADS)

    Belitsky, A. V.

    2016-12-01

    The Operator Product Expansion approach to scattering amplitudes in maximally supersymmetric gauge theory operates in terms of pentagon transitions for excitations propagating on a color flux tube. These obey a set of axioms which allow one to determine them to all orders in 't Hooft coupling and confront against explicit calculations. One of the simplifying features of the formalism is the factorizability of multiparticle transitions in terms of single-particle ones. In this paper we extend an earlier consideration of a sector populated by one kind of excitations to the case of a system with fermionic as well as bosonic degrees of freedom to address the origin of the factorization. While the purely bosonic case was analyzed within an integrable noncompact open-spin chain model, the current case is solved in the framework of a supersymmetric sl (2 | 1) magnet. We find the eigenfunctions for the multiparticle system making use of the R-matrix approach. Constructing resulting pentagon transitions, we prove their factorized form. The discussion corresponds to leading order of perturbation theory.

  20. Reconnection Between Twisted Flux Tubes - Implications for Coronal Heating

    NASA Astrophysics Data System (ADS)

    Knizhnik, K. J.; Antiochos, S. K.; DeVore, C. R.; Klimchuk, J. A.; Wyper, P. F.

    2015-12-01

    The nature of the heating of the Sun's corona has been a long-standing unanswered problem in solar physics. Beginning with the work of Parker (1972), many authors have argued that the corona is continuously heated through numerous small-scale reconnection events known as nanoflares. In these nanoflare models, stressing of magnetic flux tubes by photospheric motions causes the field to become misaligned, producing current sheets in the corona. These current sheets then reconnect, converting the free energy stored in the magnetic field into heat. In this work, we use the Adaptively Refined MHD Solver (ARMS) to perform 3D MHD simulations that dynamically resolve regions of strong current to study the reconnection between twisted flux tubes in a plane-parallel Parker configuration. We investigate the energetics of the process, and show that the flux tubes accumulate stress gradually before undergoing impulsive reconnection. We study the motion of the individual field lines during reconnection, and demonstrate that the connectivity of the configuration becomes extremely complex, with multiple current sheets being formed, which could lead to enhanced heating. In addition, we show that there is considerable interaction between the twisted flux tubes and the surrounding untwisted field, which contributes further to the formation of current sheets. The implications for observations will be discussed. This work was funded by a NASA Earth and Space Science Fellowship, and by the NASA TR&T Program.

  1. 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.

  2. Modeling the Subsurface Evolution of Active-Region Flux Tubes

    NASA Astrophysics Data System (ADS)

    Fan, Y.

    2009-12-01

    I present results from a set of 3-D spherical-shell MHD simulations of the buoyant rise of active region flux tubes in the solar interior that put new constraints on the initial twist of the subsurface tubes in order for them to emerge with tilt angles consistent with the observed Joy's law for the mean tilt of solar active regions. Due to asymmetric stretching of the Ω-shaped tube by the Coriolis force, a field strength asymmetry develops with the leading side having a greater field strength and thus being more cohesive compared to the following side. Furthermore, the magnetic flux in the leading leg shows more coherent values of local twist α ≡ JB / B2, whereas the values in the following leg show large fluctuations and are of mixed signs.

  3. CURRENT BUILDUP IN EMERGING SERPENTINE FLUX TUBES

    SciTech Connect

    Pariat, E.; Masson, S.; Aulanier, G.

    2009-08-20

    The increase of magnetic flux in the solar atmosphere during active-region formation involves the transport of the magnetic field from the solar convection zone through the lowest layers of the solar atmosphere, through which the plasma {beta} changes from >1 to <1 with altitude. The crossing of this magnetic transition zone requires the magnetic field to adopt a serpentine shape also known as the sea-serpent topology. In the frame of the resistive flux-emergence model, the rising of the magnetic flux is believed to be dynamically driven by a succession of magnetic reconnections which are commonly observed in emerging flux regions as Ellerman bombs. Using a data-driven, three-dimensional (3D) magnetohydrodynamic numerical simulation of flux emergence occurring in active region 10191 on 2002 November 16-17, we study the development of 3D electric current sheets. We show that these currents buildup along the 3D serpentine magnetic-field structure as a result of photospheric diverging horizontal line-tied motions that emulate the observed photospheric evolution. We observe that reconnection can not only develop following a pinching evolution of the serpentine field line, as usually assumed in two-dimensional geometry, but can also result from 3D shearing deformation of the magnetic structure. In addition, we report for the first time on the observation in the UV domain with the Transition Region and Coronal Explorer (TRACE) of extremely transient loop-like features, appearing within the emerging flux domain, which link several Ellermam bombs with one another. We argue that these loop transients can be explained as a consequence of the currents that build up along the serpentine magnetic field.

  4. Doppler displacements in kink MHD waves in solar flux tubes

    NASA Astrophysics Data System (ADS)

    Goossens, Marcel; Van Doorsselaere, Tom; Terradas, Jaume; Verth, Gary; Soler, Roberto

    Doppler displacements in kink MHD waves in solar flux tubes Presenting author: M. Goossens Co-authors: R. Soler, J. Terradas, T. Van Doorsselaere, G. Verth The standard interpretation of the transverse MHD waves observed in the solar atmosphere is that they are non-axisymmetric kink m=1) waves on magnetic flux tubes. This interpretation is based on the fact that axisymmetric and non-axisymmetric fluting waves do not displace the axis of the loop and the loop as a whole while kink waves indeed do so. A uniform transverse motion produces a Doppler displacement that is constant across the magnetic flux tube. A recent development is the observation of Doppler displacements that vary across the loop. The aim of the present contribution is to show that spatial variations of the Doppler displacements across the loop can be caused by kink waves. The motion associated with a kink wave is purely transverse only when the flux tube is uniform and sufficiently thin. Only in that case do the radial and azimuthal components of displacement have the same amplitude and is the azimuthal component a quarter of a period ahead of the radial component. This results in a unidirectional or transverse displacement. When the flux tube is non-uniform and has a non-zero radius the conditions for the generation of a purely transverse motion are not any longer met. In that case the motion in a kink wave is the sum of a transverse motion and a non-axisymmetric rotational motion that depends on the azimuthal angle. It can produce complicated variations of the Doppler displacement across the loop. I shall discuss the various cases of possible Doppler displacenents that can occur depending on the relative sizes of the amplitudes of the radial and azimuthal components of the displacement in the kink wave and on the orientation of the line of sight.

  5. Pair creation in an electric flux tube and chiral anomaly

    SciTech Connect

    Iwazaki, Aiichi

    2009-11-15

    Using the chiral anomaly, we discuss the pair creation of massless fermions under the effect of a magnetic field B-vector when an electric flux tube E-vector parallel to B-vector is switched on. The tube is axially symmetric and infinitely long. For the constraint B>>E, we can analytically obtain the spatial and temporal behaviors of the number density of the fermions, the azimuthal magnetic field generated by the fermions, and so on. We find that the lifetime t{sub c} of the electric field becomes shorter as the width of the tube becomes narrower. Applying it to the plasma in high-energy heavy-ion collisions, we find that the color electric field decays quickly such that t{sub c}{approx_equal}Q{sub s}{sup -1}, in which Q{sub s} is the saturation momentum.

  6. High-energy X-ray detection of G359.89–0.08 (SGR A–E): Magnetic flux tube emission powered by cosmic rays?

    SciTech Connect

    Zhang, Shuo; Hailey, Charles J.; Gotthelf, Eric V.; Mori, Kaya; Nynka, Melania; Baganoff, Frederick K.; Bauer, Franz E.; Boggs, Steven E.; Craig, William W.; Tomsick, John A.; Christensen, Finn E.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

    2014-03-20

    We report the first detection of high-energy X-ray (E > 10 keV) emission from the Galactic center non-thermal filament G359.89–0.08 (Sgr A–E) using data acquired with the Nuclear Spectroscopic Telescope Array (NuSTAR). The bright filament was detected up to ∼50 keV during a NuSTAR Galactic center monitoring campaign. The featureless power-law spectrum with a photon index Γ ≈ 2.3 confirms a non-thermal emission mechanism. The observed flux in the 3-79 keV band is F{sub X} = (2.0 ± 0.1) × 10{sup –12} erg cm{sup –2} s{sup –1}, corresponding to an unabsorbed X-ray luminosity L{sub X} = (2.6 ± 0.8) × 10{sup 34} erg s{sup –1} assuming a distance of 8.0 kpc. Based on theoretical predictions and observations, we conclude that Sgr A–E is unlikely to be a pulsar wind nebula (PWN) or supernova remnant-molecular cloud (SNR-MC) interaction, as previously hypothesized. Instead, the emission could be due to a magnetic flux tube which traps TeV electrons. We propose two possible TeV electron sources: old PWNe (up to ∼100 kyr) with low surface brightness and radii up to ∼30 pc or MCs illuminated by cosmic rays (CRs) from CR accelerators such as SNRs or Sgr A*.

  7. Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Moore, R. L.

    2003-01-01

    We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from AR10030 on 2002 July 15. The TRACE CIV observations clearly show a flux tube that is helical and that is erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption starts 25 seconds after the peak of the flare s strongest impulsive spike of microwave gryosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double CME. The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection heats the two-ribbon flare and might or might not produce the helix. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is associated with rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel, and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation. However, the observations are compatible with internal reconnection in a sheared magnetic arcade in the formation and eruption of the helix.

  8. Pentaquark in the flux tube model

    NASA Astrophysics Data System (ADS)

    Iwasaki, M.; Takagi, F.

    2008-03-01

    We propose a model for pentaquarks in an excited state in the flux tube picture. The pentaquark is assumed to be composed of two diquarks and an antiquark connected by a color flux tube with a junction. If the pentaquark is rotating rapidly, it is polarized into two clusters: one is a diquark and the other is an antiquark plus another diquark. Excited energy of this quasilinear system is calculated with the use of the WKB approximation. It is predicted that there exist quasistable excited pentaquarks: 1690MeV(3/2+), 2000MeV(5/2-), 2250MeV(7/2+) etc., which decay mainly through three-body modes.

  9. 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.

  10. Eruption of a Multiple-Turn Helical Magnetic Flux Tube in a Large Flare: Evidence for External and Internal Reconnection that Fits the Breakout Model of Solar Magnetic Eruptions

    NASA Technical Reports Server (NTRS)

    Gary, G. Allen; Moore, R. L.

    2004-01-01

    We present observations and an interpretation of a unique multiple-turn spiral flux tube eruption from active region 10030 on 2002 July 15. The TRACE C IV observations clearly show a flux tube that is helical and erupting from within a sheared magnetic field. These observations are interpreted in the context of the breakout model for magnetic field explosions. The initiation of the helix eruption. as determined by a linear backward extrapolation, starts 25 s after the peak of the flare's strongest impulsive spike of microwave gyrosynchrotron radiation early in the flare s explosive phase, implying that the sheared core field is not the site of the initial reconnection. Within the quadrupolar configuration of the active region, the external and internal reconnection sites are identified in each of two consecutive eruptive flares that produce a double coronal mass ejection (CME). The first external breakout reconnection apparently releases an underlying sheared core field and allows it to erupt, leading to internal reconnection in the wake of the erupting helix. This internal reconnection releases the helix and heats the two-ribbon flare. These events lead to the first CME and are followed by a second breakout that initiates a second and larger halo CME. The strong magnetic shear in the region is compatible with the observed rapid proper motion and evolution of the active region. The multiple-turn helix originates from above a sheared-field magnetic inversion line within a filament channel. and starts to erupt only after fast breakout reconnection has started. These observations are counter to the standard flare model and support the breakout model for eruptive flare initiation.

  11. A Multiple Flux-tube Solar Wind Model

    NASA Astrophysics Data System (ADS)

    Pinto, Rui F.; Rouillard, Alexis P.

    2017-04-01

    We present a new model, MULTI-VP, which computes the three-dimensional structure of the solar wind and includes the chromosphere, the transition region, and the corona and low heliosphere. MULTI-VP calculates a large ensemble of wind profiles flowing along open magnetic field lines that sample the entire three-dimensional atmosphere or, alternatively, a given region of interest. The radial domain starts from the photosphere and typically extends to about 30 {R}ȯ . The elementary uni-dimensional wind solutions are based on a mature numerical scheme that was adapted in order to accept any flux-tube geometry. We discuss here the first results obtained with this model. We use Potential Field Source-surface extrapolations of magnetograms from the Wilcox Solar Observatory to determine the structure of the background magnetic field. Our results support the hypothesis that the geometry of the magnetic flux-tubes in the lower corona controls the distribution of slow and fast wind flows. The inverse correlation between density and speed far away from the Sun is a global effect resulting from small readjustments of the flux-tube cross-sections in the high corona (necessary to achieve global pressure balance and a uniform open flux distribution). In comparison to current global MHD models, MULTI-VP performs much faster and does not suffer from spurious cross-field diffusion effects. We show that MULTI-VP has the capability to predict correctly the dynamical and thermal properties of the background solar wind (wind speed, density, temperature, magnetic field amplitude, and other derived quantities) and to approach real-time operation requirements.

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Long-lived auroral structures and atmospheric losses through auroral flux tubes on Mars

    NASA Astrophysics Data System (ADS)

    Dubinin, E.; Fraenz, M.; Woch, J.; Barabash, S.; Lundin, R.

    2009-04-01

    The ASPERA-3 observations of electron and ion fluxes over the regions dominated by crustal magnetic fields show the existence of long-lived and active aurora-type magnetic flux tubes with a width of 20-150 km. The activity manifests itself by large electron energy fluxes (≥10-4 W/m2) and strong distortions in the upper (350-400 km) ionosphere. In some events the peaked electron energy distributions typical for Earth aurora are so pronounced that they are present in velocity distribution functions. A significant depletion of such auroral flux tubes is accompanied by the appearance of oxygen beams and a heating of the ions of ionospheric origin. Auroral activity was observed on several subsequent orbits of the Mars Express spacecraft during more than two weeks implying a stable existence of aurora on Mars. Atmospheric loss driven by energy deposition in the auroral flux tubes is estimated as ˜1023 s-1.

  17. Investigating the Dynamics of Canonical Flux Tubes in Jet Geometry

    NASA Astrophysics Data System (ADS)

    Lavine, Eric; You, Setthivoine

    2014-10-01

    Highly collimated plasma jets are frequently observed at galactic, stellar, and laboratory scales. Some models suppose these jets are magnetohydrodynamically-driven magnetic flux tubes filled with flowing plasma, but they do not agree on a collimation process. Some evidence supporting a universal MHD pumping mechanism has been obtained from planar electrode experiments with aspect ratios of ~10:1 however, these jets are subject to kink instabilities beyond a certain length and are unable to replicate the remarkable aspect ratios (10-1000:1) seen in astrophysical systems. Other models suppose these jets are flowing Z-pinch plasmas and experiments that use stabilizing shear flows have achieved aspect ratios of ~30:1, but are line tied at both ends. Can both collimation and stabilization mechanisms work together to produce long jets without kink instabilities and only one end tied to the central object? This question is evaluated from the point of view of canonical flux tubes and canonical helicity transport, indicating that jets can become long and collimated due to a combination of strong helical shear flows and conversion of magnetic helicity into kinetic helicity. The MOCHI LabJet experiment is designed to study this in the laboratory. Supported by US DoE Early Career Grant DE-SC0010340.

  18. Force-free thin flux tubes: Basic equations and stability

    NASA Astrophysics Data System (ADS)

    Zhugzhda, Y. D.

    1996-01-01

    The thin flux tube approximation is considered for a straight, symmetrical, force-free, rigidly rotating flux tube. The derived set of equations describes tube, body sausage, and Alfvén wave modes and is valid for any values of β. The linear waves and instabilities of force-free flux tubes are considered. The comparison of approximate and exact solutions for an untwisted, nonrotating flux tube is performed. It is shown that the approximate and exact dispersion equations coincides, except the 20% discrepancy of sausage frequencies. An effective cross section is proposed to introduce the removal of this discrepancy. It makes the derived approximation correct for the force-free thin flux tube dynamics, except the detailed structure of radial eigenfunction. The dispersion of Alfvén torsional waves in a force-free tubes appears. The valve effect of one directional propagation of waves in rotating twisted tube is revealed. The current and rotational sausage instabilities of a force-free, thin flux tube are considered.

  19. Flux Transfer Events Simultaneously Observed by Polar and Cluster: Flux Rope in the Subsolar Region and Flux Tube Addition to the Polar Cusp

    NASA Technical Reports Server (NTRS)

    Le, G.; Zheng, Y.; Russell, C. T.; Pfaff, R. F.; Lin, N.; Slavin, J. A.; Parks, G.; Wilber, M.; Petrinec, S. M.; Lucek, E. A.; Reme, H.

    2007-01-01

    The phenomenon called flux transfer events (FTEs) is widely accepted as the manifestation of time-dependent reconnection. In this paper, we present observational evidence of a flux transfer event observed simultaneously at low-latitude by Polar and at high-latitude by Cluster. This event occurs on March 21, 2002, when both Cluster and Polar are located near local noon but with a large latitudinal separation. During the event, Cluster is moving outbound from the polar cusp to the magnetosheath, and Polar is in the magnetosheath near the equatorial magnetopause. The observations show that a flux transfer event occurs between the equator and the northern cusp. Polar and Cluster observe the FTE s two open flux tubes: Polar encounters the southward moving flux tube near the equator; and Cluster the northward moving flux tube at high latitude. The low latitude FTE appears to be a flux rope with helical magnetic field lines as it has a strong core field and the magnetic field component in the boundary normal direction exhibits a strong bi-polar variation. Unlike the low-latitude FTE, the high-latitude FTE observed by Cluster does not exhibit the characteristic bi-polar perturbation in the magnetic field. But the plasma data clearly reveal its open flux tube configuration. It shows that the magnetic field lines have straightened inside the FTE and become more aligned to the neighboring flux tubes as it moves to the cusp. Enhanced electrostatic fluctuations have been observed within the FTE core, both at low- and high-latitudes. This event provides a unique opportunity to understand high-latitude FTE signatures and the nature of time-varying reconnection.

  20. 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

  1. 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.

  2. 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.

  3. New constraint on effective field theories of the QCD flux tube

    NASA Astrophysics Data System (ADS)

    Baker, M.

    2016-03-01

    Effective magnetic S U (N ) gauge theory with classical ZN flux tubes of intrinsic width 1/M is an effective field theory of the long-distance quark-antiquark interaction in S U (N ) Yang-Mills theory. Long-wavelength fluctuations of the ZN vortices of this theory lead to an effective string theory. In this paper, we clarify the connection between effective field theory and effective string theory, and we propose a new constraint on these vortices. We first examine the impact of string fluctuations on the classical dual superconductor description of confinement. At interquark distances R ˜1/M , the classical action for a straight flux tube determines the heavy quark potentials. At distances R ≫1/M , fluctuations of the flux tube axis x ˜ give rise to an effective string theory with an action Seff(x ˜), the classical action for a curved flux tube, evaluated in the limit 1/M →0 . This action is equal to the Nambu-Goto action. These conclusions are independent of the details of the ZN flux tube. Further, we assume the QCD flux tube satisfies the additional constraint, ∫0∞r d r T/θθ(r ) r2=0 , where T/θθ(r ) r2 is the value of the θ θ component of the stress tensor at a distance r from the axis of an infinite flux tube. Under this constraint, the string tension σ equals the force on a quark in the chromoelectric field E → of an infinite straight flux tube, and the Nambu-Goto action can be represented in terms of the chromodynamic fields of effective magnetic S U (N ) gauge theory, yielding a field theory interpretation of effective string theory.

  4. Colour flux-tubes in static pentaquark and tetraquark systems

    NASA Astrophysics Data System (ADS)

    Bicudo, Pedro; Cardoso, Nuno; Cardoso, Marco

    2012-04-01

    The colour fields created by the static tetraquark and pentaquark systems are computed in quenched SU(3) lattice QCD, with gauge invariant lattice operators, in a 243×48 lattice at β=6.2. We generate our quenched configurations with GPUs, and detail the respective benchmarks in different SU(N) groups. While at smaller distances the Coulomb potential is expected to dominate, at larger distances it is expected that fundamental flux tubes, similar to the flux-tube between a quark and an antiquark, emerge and confine the quarks. In order to minimize the potential the fundamental flux tubes should connect at 120° angles. We compute the square of the colour fields utilizing plaquettes, and locate the static sources with generalized Wilson loops and with APE smearing. The tetraquark system is well described by a double-Y-shaped flux-tube, with two Steiner points, but when quark-antiquark pairs are close enough the two junctions collapse and we have an X-shaped flux-tube, with one Steiner point. The pentaquark system is well described by a three-Y-shaped flux-tube where the three flux junctions are Steiner points.

  5. J/ ψ-dissociation by a color electric flux tube

    NASA Astrophysics Data System (ADS)

    Loh, S.; Greiner, C.; Mosel, U.

    1997-02-01

    We address the question of how a c - c¯state (a J/ ψ) can be dissociated by the strong color electric fields when moving through a color electric flux tube. The color electric flux tube and the dissociation of the heavy quarkonia state are both described within the Friedberg-Lee color dielectric model. We speculate on the importance of such an effect with respect to the observed J/ ψ-suppression in ultrarelativistic heavy ion collisions.

  6. DYNAMICS OF MAGNETIZED VORTEX TUBES IN THE SOLAR CHROMOSPHERE

    SciTech Connect

    Kitiashvili, I. N.; Kosovichev, A. G.; Mansour, N. N.; Wray, A. A.

    2012-05-20

    We use three-dimensional radiative MHD simulations to investigate the formation and dynamics of small-scale (less than 0.5 Mm in diameter) vortex tubes spontaneously generated by turbulent convection in quiet-Sun regions with an initially weak (10 G) mean magnetic field. The results show that the vortex tubes penetrate into the chromosphere and substantially affect the structure and dynamics of the solar atmosphere. The vortex tubes are mostly concentrated in intergranular lanes and are characterized by strong (near sonic) downflows and swirling motions that capture and twist magnetic field lines, forming magnetic flux tubes that expand with height and attain magnetic field strengths ranging from 200 G in the chromosphere to more than 1 kG in the photosphere. We investigate in detail the physical properties of these vortex tubes, including thermodynamic properties, flow dynamics, and kinetic and current helicities, and conclude that magnetized vortex tubes provide an important path for energy and momentum transfer from the convection zone into the chromosphere.

  7. A Flux Tube Solar Dynamo Model Based on the Competing Role of Buoyancy and Downflows

    NASA Astrophysics Data System (ADS)

    Li, L. H.; Sofia, S.; Belvedere, G.

    2005-08-01

    A magnetic flux tube can be considered both as a separate body and as a confined field. As a field, it is affected by both differential rotation (Ω-effect) and cyclonic convection (α-effect). As a body, the tube experiences not only a buoyant force, but also a dynamic pressure due to downflows above the tube. These two competing dynamic effects are incorporated into the α-Ω dynamo equations through the total magnetic turbulent diffusivity, leading to a flux tube dynamo operating in the convection zone. We analyze and solve the extended dynamo equations in the linear approximation by adopting the observed solar internal rotation and assuming a downflow effect derived from numerical simulations of a solar convection zone. The model reproduces the 22 yr cycle period; the extended butterfly diagram with the confinement of strong activity to low heliographic latitudes |Φ|<=35deg the evidence that at low latitudes the radial field is in an approximately π phase lag compared to the toroidal field at the same latitude; the evidence that the poleward branch is in a π/2 phase lag with respect to the equatorward branch; and the evidence that most of the magnetic flux is present in an intermittent form, concentrated into strong flux tubes.

  8. 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).

  9. Flux-tube geometry and solar wind speed during an activity cycle

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    Context. The solar wind speed at 1 AU shows cyclic variations in latitude and in time which reflect the evolution of the global background magnetic field during the activity cycle. It is commonly accepted that the terminal (asymptotic) wind speed in a given magnetic flux-tube is generally anti-correlated with its total expansion ratio, which motivated the definition of widely used semi-empirical scaling laws relating one to the other. In practice, such scaling laws require ad hoc corrections (especially for the slow wind in the vicinities of streamer/coronal hole boundaries) and empirical fits to in situ spacecraft data. A predictive law based solely on physical principles is still missing. Aims: We test whether the flux-tube expansion is the controlling factor of the wind speed at all phases of the cycle and at all latitudes (close to and far from streamer boundaries) using a very large sample of wind-carrying open magnetic flux-tubes. We furthermore search for additional physical parameters based on the geometry of the coronal magnetic field which have an influence on the terminal wind flow speed. Methods: We use numerical magneto-hydrodynamical simulations of the corona and wind coupled to a dynamo model to determine the properties of the coronal magnetic field and of the wind velocity (as a function of time and latitude) during a whole 11-yr activity cycle. These simulations provide a large statistical ensemble of open flux-tubes which we analyse conjointly in order to identify relations of dependence between the wind speed and geometrical parameters of the flux-tubes which are valid globally (for all latitudes and moments of the cycle). Results: Our study confirms that the terminal (asymptotic) speed of the solar wind depends very strongly on the geometry of the open magnetic flux-tubes through which it flows. The total flux-tube expansion is more clearly anti-correlated with the wind speed for fast rather than for slow wind flows, and effectively controls the

  10. 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.

  11. On the relation between coronal heating, flux tube divergence, and the solar wind proton flux and flow speed

    NASA Technical Reports Server (NTRS)

    Sandbaek, Onulf; Leer, Egil; Hansteen, Viggo H.

    1994-01-01

    A one-fluid solar wind model is used to investigate some relations between coronal heating, the flux tube divergence near the Sun, and the solar wind proton flux and flow speed. The effects of energy addition to the supersonic region of the flow are also studied. We allow for a mechanical energy flux that heats the corona, and an Alfven wave energy flux that adds energy, mainly to the supersonic flow, both as momentum and as heat. We find that the mechanical energy flux determines the solar wind mass flux, and in order to keep an almost constant proton flux at the orbit of Earth with changing flow geometry, that the mechanical energy flux must vary linearly with the magnetic field in the inner corona. This thermally driven wind generally has a low asymptotic flow speed. When Alfven waves are added to the thermally driven flow, the asymptotic flow speed is increased and is determined by the ratio of the Alfven wave and the mechanical energy fluxes at the coronal base. Flow speeds characteristic of recurrent high-speed solar wind streams can be obtained only when the Alfven wave energy flux, deposited in the supersonic flow, is larger than the mechanical energy flux heating the corona.

  12. Flux tube spectra from approximate integrability at low energies

    NASA Astrophysics Data System (ADS)

    Dubovsky, S.; Flauger, R.; Gorbenko, V.

    2015-03-01

    We provide a detailed introduction to a method we recently proposed for calculating the spectrum of excitations of effective strings such as QCD flux tubes. The method relies on the approximate integrability of the low-energy effective theory describing the flux tube excitations and is based on the thermodynamic Bethe ansatz. The approximate integrability is a consequence of the Lorentz symmetry of QCD. For excited states, the convergence of the thermodynamic Bethe ansatz technique is significantly better than that of the traditional perturbative approach. We apply the new technique to the lattice spectra for fundamental flux tubes in gluodynamics in D = 3 + 1 and D = 2 + 1, and to k-strings in gluodynamics in D = 2 + 1. We identify a massive pseudoscalar resonance on the worldsheet of the confining strings in SU(3) gluodynamics in D = 3 + 1, and massive scalar resonances on the worldsheet of k = 2.3 strings in SU(6) gluodynamics in D = 2 + 1.

  13. Benchmarking Particle-in-Cell drift wave simulations with Eulerian simulations in a flux-tube

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Parker, Scott; Wan, Weigang; Bravenec, Ronald; Wang, Eric; Candy, Jeff

    2012-10-01

    We present the implementation of a flux-tube option in the global turbulence code GEM.footnotetextY. Chen and S. E. Parker, J. Comp. Phys. 220, 839 (2007) This is necessary for benchmarking purposes because of the immense complexity involved in comparing global simulations. The global GEM assumes the magnetic equilibrium to be completely given. Our initial flux-tube implementation simply selects a radial location as the center of the flux-tube and a radial size of the flux-tube, sets all equilibrium quantities (B, ∇B, T, ∇T, the Jacobian etc.) to be equal to their values at the center of the flux-tube, and retains only a linear radial profile of the safety factor needed for boundary conditions. We found good agreement between GEM and GYRO/GS2 for the mode frequency/growth rate in the case of adiabatic electrons, but a difference of ˜15% in the growth rates when kinetic electrons are included. Our goal is to understand the origin of this moderate disagreement. An alternative local geometry model based on a local solution of the Grad-Shafranov equationfootnotetextJ. Candy, Plasma Phys. Control. Fusion 51, 105009 (2009) has been implemented and new benchmarking results from this model will be presented.

  14. Signature of the Fragmentation of a Color Flux Tube

    SciTech Connect

    Wong, Cheuk-Yin

    2015-10-07

    The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of the local conservation of momentum and charge, the production of a $q$-$\\bar q$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced pions however can be signalled by the their rapidity difference $\\Delta y$ falling within the window of $|\\Delta y | < 1/(dN_\\pi/dy)$, on account of the space-time-rapidity ordering of produced pions in a flux tube fragmentation. Therefore, the local conservation of momentum will lead to a suppression of azimuthal two-pion correlation $dN/(d\\Delta \\phi\\, d\\Delta y)$ on the near side at $(\\Delta \\phi, \\Delta y) \\sim 0$, but an enhanced azimuthal correlation on the back-to-back, away side at $(\\Delta \\phi$$\\sim$$ \\pi,\\Delta y$$\\sim$0). Similarly, in a flux tube fragmentation, the local conservation of charge will forbid the production of like charge pions within $|\\Delta y | < 1/(dN_\\pi/dy)$, but there is no such prohibition for $|\\Delta y| >1/(dN_\\pi/dy)$. These properties may be used as the signature for the fragmentation of a color flux tube.

  15. Signature of the Fragmentation of a Color Flux Tube

    DOE PAGES

    Wong, Cheuk-Yin

    2015-10-07

    The production of quark-antiquark pairs along a color flux tube precedes the fragmentation of the tube. Because of the local conservation of momentum and charge, the production of amore » $q$-$$\\bar q$$ pair will lead to correlations of adjacently produced mesons (mostly pions). Adjacently produced pions however can be signalled by the their rapidity difference $$\\Delta y$$ falling within the window of $$|\\Delta y | < 1/(dN_\\pi/dy)$$, on account of the space-time-rapidity ordering of produced pions in a flux tube fragmentation. Therefore, the local conservation of momentum will lead to a suppression of azimuthal two-pion correlation $$dN/(d\\Delta \\phi\\, d\\Delta y)$$ on the near side at $$(\\Delta \\phi, \\Delta y) \\sim 0$$, but an enhanced azimuthal correlation on the back-to-back, away side at $$(\\Delta \\phi$$$\\sim$$$ \\pi,\\Delta y$$$\\sim$$0). Similarly, in a flux tube fragmentation, the local conservation of charge will forbid the production of like charge pions within $$|\\Delta y | < 1/(dN_\\pi/dy)$$, but there is no such prohibition for $$|\\Delta y| >1/(dN_\\pi/dy)$$. These properties may be used as the signature for the fragmentation of a color flux tube.« less

  16. The Color Flux Tube as an Effective String

    NASA Astrophysics Data System (ADS)

    Pepe, Michele

    2011-05-01

    We investigate the low-energy regime of the confining string connecting color sources in Yang-Mills theory. First, we present results of the Monte Carlo measurement of the width of the flux tube between two static quarks in the fundamental representation both at zero and at finite temperature. Then we consider the confining flux tube connecting color sources in larger representations of the gauge group. For stable strings—the k-strings—we study the Luscher term; for unstable strings we investigate their decay as the distance between the static sources is increased.

  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. 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.

  19. 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

  20. 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.

  1. Quasi-steady multiple flux tubes induced by localized current perturbation in toroidal plasma

    NASA Astrophysics Data System (ADS)

    Yun, Gunsu

    2015-11-01

    Quasi-steady helical modes with dual, triple, or more flux tubes are easily produced by localized current drive in the core of sawtoothing plasma on the KSTAR tokamak. Individual flux tubes have m / n = 1 / 1 helicity, co-rotate around the magnetic axis, and later merge into a single m = 1 mode. The merged mode eventually crashes with rapid collapse of the core pressure and the next cycle repeats the same pattern, exhibiting sawtooth-like oscillations in the core pressure. The generation mechanism of multiple flux tubes (MFTs) has been studied in two different approaches to understand the observed trend that the number of flux tubes increases as the current drive location moves away from the magnetic axis up to about the magnetic surface of the safety factor q = 1 at the mode collapse: (1) nonlinear reduced MHD simulation with a localized current source modeling the time-varying interaction between the current source and flux tubes and (2) linear MHD simulation with a prescribed q profile with a radially localized current blip. Both studies show that MFTs can be produced only in plasmas with nearly flat q profile close to unity, suggesting the collapse of the m = 1 mode (i.e., sawtooth crash) is complete. Recent observation of long-lived MFTs induced by localized current drive in non-sawtoothing plasma suggests that q profile evolution toward lower- m instability is required for the merging and crash of MFTs. Work supported by the National Research Foundation of Korea, US D.O.E., and Japan Society for the Promotion of Science.

  2. SURFACE ALFVEN WAVES IN SOLAR FLUX TUBES

    SciTech Connect

    Goossens, M.; Andries, J.; Soler, R.; Van Doorsselaere, T.; Arregui, I.; Terradas, J.

    2012-07-10

    Magnetohydrodynamic (MHD) waves are ubiquitous in the solar atmosphere. Alfven waves and magneto-sonic waves are particular classes of MHD waves. These wave modes are clearly different and have pure properties in uniform plasmas of infinite extent only. Due to plasma non-uniformity, MHD waves have mixed properties and cannot be classified as pure Alfven or magneto-sonic waves. However, vorticity is a quantity unequivocally related to Alfven waves as compression is for magneto-sonic waves. Here, we investigate MHD waves superimposed on a one-dimensional non-uniform straight cylinder with constant magnetic field. For a piecewise constant density profile, we find that the fundamental radial modes of the non-axisymmetric waves have the same properties as surface Alfven waves at a true discontinuity in density. Contrary to the classic Alfven waves in a uniform plasma of infinite extent, vorticity is zero everywhere except at the cylinder boundary. If the discontinuity in density is replaced with a continuous variation of density, vorticity is spread out over the whole interval with non-uniform density. The fundamental radial modes of the non-axisymmetric waves do not need compression to exist unlike the radial overtones. In thin magnetic cylinders, the fundamental radial modes of the non-axisymmetric waves with phase velocities between the internal and the external Alfven velocities can be considered as surface Alfven waves. On the contrary, the radial overtones can be related to fast-like magneto-sonic modes.

  3. MULTI-PARAMETRIC STUDY OF RISING 3D BUOYANT FLUX TUBES IN AN ADIABATIC STRATIFICATION USING AMR

    SciTech Connect

    Martínez-Sykora, Juan; Cheung, Mark C. M.; Moreno-Insertis, Fernando

    2015-11-20

    We study the buoyant rise of magnetic flux tubes embedded in an adiabatic stratification using two-and three-dimensional, magnetohydrodynamic simulations. We analyze the dependence of the tube evolution on the field line twist and on the curvature of the tube axis in different diffusion regimes. To be able to achieve a comparatively high spatial resolution we use the FLASH code, which has a built-in Adaptive Mesh Refinement (AMR) capability. Our 3D experiments reach Reynolds numbers that permit a reasonable comparison of the results with those of previous 2D simulations. When the experiments are run without AMR, hence with a comparatively large diffusivity, the amount of longitudinal magnetic flux retained inside the tube increases with the curvature of the tube axis. However, when a low-diffusion regime is reached by using the AMR algorithms, the magnetic twist is able to prevent the splitting of the magnetic loop into vortex tubes and the loop curvature does not play any significant role. We detect the generation of vorticity in the main body of the tube of opposite sign on the opposite sides of the apex. This is a consequence of the inhomogeneity of the azimuthal component of the field on the flux surfaces. The lift force associated with this global vorticity makes the flanks of the tube move away from their initial vertical plane in an antisymmetric fashion. The trajectories have an oscillatory motion superimposed, due to the shedding of vortex rolls to the wake, which creates a Von Karman street.

  4. 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.

  5. Flux tubes embedded into reconnection outflows in the solar wind

    NASA Astrophysics Data System (ADS)

    Voros, Z.; Zaqarashvili, T.; Sasunov, Y.; Narita, Y.

    2015-12-01

    Reconnection exhausts in the solar wind are usually interpreted in terms of a quasi-stationary Petschek-type reconnection model. Accordingly, within a region of magnetic field reversal, the wedge-shaped, Alfvenic accelerated plasma outflow is bounded by layers containing (anti-) correlated components of speed and magnetic field fluctuations. However, time-dependent impulsive reconnection can generate flux ropes embedded into accelerated outflows. Reconnection associated moving flux ropes or plasmoids are frequently observed in the Earth's magnetotail, while similar observations are missing in the solar wind. We present the first observations of small-scale magnetic flux ropes associated with reconnection exhausts in the solar wind, using the data from the WIND probe. We argue that the interaction of moving flux ropes with the background plasma can generate turbulence leading finally to the local heating of the solar wind.

  6. Dynamics of Quarks in a 2D Flux Tube

    SciTech Connect

    Koshelkin, Andrey V.; Wong, Cheuk-Yin

    2015-01-01

    On the basis of a compactification of the (3+1) into (1+1) dimensional space-time [1], the quark states inside the 2D flux tube are studied for the case of a linear transverse confining potential. The derived states are classified by both the projections of the orbital momentum and the spin along the tube direction. The spectrum of the fermion states is evaluated. It is found that the energy eigenvalues of the quarks appear to be approximately related to the square root of the eigenvalues of the two-dimensional harmonic oscillator.

  7. 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

  8. Detection of Cracks at Welds in Steel Tubing Using Flux Focusing Electromagnetic Probe

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Simpson, John; Namkung, Min

    1994-01-01

    The inspection of weldments in critical pressure vessel joints is a major concern in the nuclear power industry. Corrosive environments can speed the fatigue process and access to the critical area is often limited. Eddy current techniques have begun to be used to help overcome these obstacles [1]. As direct contact and couplants are not required, remote areas can be inspected by simply snaking an eddy current coil into the intake tube of the vessel. The drawback of the eddy current method has been the high sensitivity to small changes in the conductivity and permeability of the test piece which are known to vary at weldments [1]. The flaw detection mechanism of the flux focusing electromagnetic probe can help alleviate these difficulties and provide a unique capability for detecting longitudinal fatigue cracks in critical tube structures. The Flux Focusing Electromagnetic Flaw Detector, originally invented for the detection of fatigue and corrosion damage in aluminum plates [2-3], has been adapted for use in testing steel tubing for longitudinal fatigue cracks. The modified design allows for the probe to be placed axisymmetrically into the tubing, inducing eddy currents in the tube wall. The pickup coil of the probe is fixed slightly below the primary windings and is rotated 90 so that its axis is normal to the tube wall. The magnetic flux of the primary coil is focused through the use of ferromagnetic material so that in the absence of fatigue damage there will be no flux linkage with the pickup coil. The presence of a longitudinal fatigue crack will cause the eddy currents induced in the tube wall to flow around the flaw and directly under the pickup coil. The magnetic field associated with these currents will then link the pickup coil and an unambiguous increase in the output voltage of the probe will be measured. The use of the flux focusing electromagnetic probe is especially suited for the detection of flaws originating at or near tube welds. The probe is

  9. SCATTERING OF THE f-MODE BY SMALL MAGNETIC FLUX ELEMENTS FROM OBSERVATIONS AND NUMERICAL SIMULATIONS

    SciTech Connect

    Felipe, T.; Braun, D.; Crouch, A.; Birch, A.

    2012-10-01

    The scattering of f-modes by magnetic tubes is analyzed using three-dimensional numerical simulations. An f-mode wave packet is propagated through a solar atmosphere embedded with three different flux tube models that differ in radius and total magnetic flux. A quiet-Sun simulation without a tube present is also performed as a reference. Waves are excited inside the flux tube and propagate along the field lines, and jacket modes are generated in the surroundings of the flux 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 magnetic flux. 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 magnetic 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 flux 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 magnetic elements and asymmetrically shaped elements.

  10. Three-dimensional magnetohydrodynamics of the emerging magnetic flux in the solar atmosphere

    NASA Technical Reports Server (NTRS)

    Matsumoto, R.; Tajima, T.; Shibata, K.; Kaisig, M.

    1993-01-01

    The nonlinear evolution of an emerging magnetic flux tube or sheet in the solar atmosphere is studied through 3D MHD simulations. In the initial state, a horizontal magnetic flux 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 magnetic flux sheet or tube is unstable against the undular mode of the magnetic buoyancy instability. The magnetic loop rises due to the linear and then later nonlinear instabilities caused by the buoyancy enhanced by precipitating the gas along magnetic field lines. We find by 3D simulation that during the ascendance of loops the bundle of flux tubes or even the flux sheet develops into dense gas filaments pinched between magnetic loops. The interchange modes help produce a fine fiber flux structure perpendicular to the magnetic field direction in the linear stage, while the undular modes determine the overall buoyant loop structure. The expansion of such a bundle of magnetic loops follows the self-similar behavior observed in 2D cases studied earlier. Our study finds the threshold flux for arch filament system (AFS) formation to be about 0.3 x 10 exp 20 Mx.

  11. Resonant behaviour of MHD waves on magnetic flux tubes. I - Connection formulae at the resonant surfaces. II - Absorption of sound waves by sunspots

    NASA Technical Reports Server (NTRS)

    Sakurai, Takashi; Goossens, Marcel; Hollweg, Joseph V.

    1991-01-01

    The present method of addressing the resonance problems that emerge in such MHD phenomena as the resonant absorption of waves at the Alfven resonance point avoids solving the fourth-order differential equation of dissipative MHD by recourse to connection formulae across the dissipation layer. In the second part of this investigation, the absorption of solar 5-min oscillations by sunspots is interpreted as the resonant absorption of sounds by a magnetic cylinder. The absorption coefficient is interpreted (1) analytically, under certain simplifying assumptions, and numerically, under more general conditions. The observed absorption coefficient magnitude is explained over suitable parameter ranges.

  12. The nonlinear gyro-kinetic flux tube code GKW

    NASA Astrophysics Data System (ADS)

    Peeters, A. G.; Camenen, Y.; Casson, F. J.; Hornsby, W. A.; Snodin, A. P.; Strintzi, D.; Szepesi, G.

    2009-12-01

    A new nonlinear gyro-kinetic flux tube code (GKW) for the simulation of micro instabilities and turbulence in magnetic confinement plasmas is presented in this paper. The code incorporates all physics effects that can be expected from a state of the art gyro-kinetic simulation code in the local limit: kinetic electrons, electromagnetic effects, collisions, full general geometry with a coupling to a MHD equilibrium code, and E×B shearing. In addition the physics of plasma rotation has been implemented through a formulation of the gyro-kinetic equation in the co-moving system. The gyro-kinetic model is five-dimensional and requires a massive parallel approach. GKW has been parallelised using MPI and scales well up to 8192+ cores. The paper presents the set of equations solved, the numerical methods, the code structure, and the essential benchmarks. Program summaryProgram title: GKW Catalogue identifier: AEES_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEES_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU GPL v3 No. of lines in distributed program, including test data, etc.: 29 998 No. of bytes in distributed program, including test data, etc.: 206 943 Distribution format: tar.gz Programming language: Fortran 95 Computer: Not computer specific Operating system: Any for which a Fortran 95 compiler is available Has the code been vectorised or parallelised?: Yes. The program can efficiently utilise 8192+ processors, depending on problem and available computer. 128 processors is reasonable for a typical nonlinear kinetic run on the latest x86-64 machines. RAM:˜128 MB-1 GB for a linear run; 25 GB for typical nonlinear kinetic run (30 million grid points) Classification: 19.8, 19.9, 19.11 External routines: None required, although the functionality of the program is somewhat limited without a MPI implementation (preferably MPI-2) and the FFTW3 library. Nature of problem: Five

  13. 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.

  14. THE EMERGENCE OF A TWISTED FLUX TUBE INTO THE SOLAR ATMOSPHERE: SUNSPOT ROTATIONS AND THE FORMATION OF A CORONAL FLUX ROPE

    SciTech Connect

    Fan, Y.

    2009-06-01

    We present a three-dimensional simulation of the dynamic emergence of a twisted magnetic flux tube from the top layer of the solar convection zone into the solar atmosphere and corona. It is found that after a brief initial stage of flux emergence during which the two polarities of the bipolar region become separated and the tubes intersecting the photosphere become vertical, significant rotational motion sets in within each polarity. The rotational motions of the two polarities are found to twist up the inner field lines of the emerged fields such that they change their orientation into an inverse configuration (i.e., pointing from the negative polarity to the positive polarity over the neutral line). As a result, a flux rope with sigmoid-shaped, dipped core fields forms in the corona, and the center of the flux rope rises in the corona with increasing velocity as the twisting of the flux rope footpoints continues. The rotational motion in the two polarities is a result of propagation of nonlinear torsional Alfven waves along the flux tube, which transports significant twist from the tube's interior portion toward its expanded coronal portion. This is a basic process whereby twisted flux ropes are developed in the corona with increasing twist and magnetic energy, leading up to solar eruptions.

  15. NUMERICAL STUDY ON THE EMERGENCE OF KINKED FLUX TUBE FOR UNDERSTANDING OF POSSIBLE ORIGIN OF δ-SPOT REGIONS

    SciTech Connect

    Takasao, Shinsuke; Shibata, Kazunari; Fan, Yuhong; Cheung, Mark C. M.

    2015-11-10

    We carried out an magnetohydrodynamic simulation where a subsurface twisted kink-unstable flux tube emerges from the solar interior to the corona. Unlike the previous expectations based on the bodily emergence of a knotted tube, we found that the kinked tube can spontaneously form a complex quadrupole structure at the photosphere. Due to the development of the kink instability before the emergence, the magnetic twist at the kinked apex of the tube is greatly reduced, although the other parts of the tube are still strongly twisted. This leads to the formation of a complex quadrupole structure: a pair of the coherent, strongly twisted spots and a narrow complex bipolar pair between it. The quadrupole is formed by the submergence of a portion of emerged magnetic fields. This result is relevant for understanding the origin of the complex multipolar δ-spot regions that have a strong magnetic shear and emerge with polarity orientations not following Hale-Nicholson and Joy Laws.

  16. 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.

  17. THE RISE OF ACTIVE REGION FLUX TUBES IN THE TURBULENT SOLAR CONVECTIVE ENVELOPE

    SciTech Connect

    Weber, Maria A.; Fan Yuhong; Miesch, Mark S.

    2011-11-01

    We use a thin flux tube model in a rotating spherical shell of turbulent convective flows to study how active region scale flux tubes rise buoyantly from the bottom of the convection zone to near the solar surface. We investigate toroidal flux tubes at the base of the convection zone with field strengths ranging from 15 kG to 100 kG at initial latitudes ranging from 1{sup 0} to 40{sup 0} with a total flux of 10{sup 22} Mx. We find that the dynamic evolution of the flux tube changes from convection dominated to magnetic buoyancy dominated as the initial field strength increases from 15 kG to 100 kG. At 100 kG, the development of {Omega}-shaped rising loops is mainly controlled by the growth of the magnetic buoyancy instability. However, at low field strengths of 15 kG, the development of rising {Omega}-shaped loops is largely controlled by convective flows, and properties of the emerging loops are significantly changed compared to previous results in the absence of convection. With convection, rise times are drastically reduced (from years to a few months), loops are able to emerge at low latitudes, and tilt angles of emerging loops are consistent with Joy's law for initial field strengths of {approx}>40 kG. We also examine other asymmetries that develop between the leading and following legs of the emerging loops. Taking all the results together, we find that mid-range field strengths of {approx}40-50 kG produce emerging loops that best match the observed properties of solar active regions.

  18. 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.

  19. AN ESTIMATE OF THE DETECTABILITY OF RISING FLUX TUBES

    SciTech Connect

    Birch, A. C.; Braun, D. C.; Fan, Y.

    2010-11-10

    The physics of the formation of magnetic active regions (ARs) is one of the most important problems in solar physics. One main class of theories suggests that ARs are the result of magnetic flux that rises from the tachocline. Time-distance helioseismology, which is based on measurements of wave propagation, promises to allow the study of the subsurface behavior of this magnetic flux. Here, we use a model for a buoyant magnetic flux concentration together with the ray approximation to show that the dominant effect on the wave propagation is expected to be from the roughly 100 m s{sup -1} retrograde flow associated with the rising flux. Using a B-spline-based method for carrying out inversions of wave travel times for flows in spherical geometry, we show that at 3 days before emergence the detection of this retrograde flow at a depth of 30 Mm should be possible with a signal-to-noise level of about 8 with a sample of 150 emerging ARs.

  20. Spectral line radiation from solar small-scale flux tubes. II

    NASA Astrophysics Data System (ADS)

    Hasan, S. S.; Kneer, F.; Kalkofen, W.

    1998-04-01

    We examine spectral line radiation from small-scale magnetic flux tubes in the solar atmosphere. This is a continuation of work by Kneer et al. (1996). The main difference with the previous investigation is in the choice of the external atmosphere. Earlier we adopted an atmosphere resembling the empirical quiet Sun model for the ambient medium. In the present study, we iteratively adjust the temperature structure of the external atmosphere to fit the Stokes I and V profiles and the average continuum intensities with those obtained from observations. Our models are hotter in the uppermost photospheric layers and cooler in the deeper layers than the quiet Sun model and agree well with semi-empirical flux tube models.

  1. Particle acceleration in three-dimensional reconnection of flux-tube disconnection

    NASA Astrophysics Data System (ADS)

    Akbari, Z.; Hosseinpour, M.; Mohammadi, M. A.

    2016-11-01

    "Flux-tube disconnection" is a type of steady-state three-dimensional magnetic reconnection with O-point at the origin of the resistive diffusion region. Magnetic reconnection is accepted as a potential mechanism for particle acceleration in astrophysical and space plasmas, especially in solar flares. By using the static magnetic and electric fields for flux-tube disconnection, features of test particle acceleration with input parameters for the solar corona are investigated. We show that a proton injected close to origin of the diffusion region can be accelerated to a very high kinetic energy along the magnetic field lines. The efficient acceleration takes place at the radial point where the electric drift velocity has its maximum magnitude. However, a proton injected at radial distances far away from the origin is not accelerated efficiently and even may be trapped in the field lines. The final kinetic energy of the particle depends significantly on the amplitude of the electric field rather than the amplitude of magnetic field.

  2. Magnetic detector for projectiles in tubes

    NASA Technical Reports Server (NTRS)

    Bogdanoff, D. W.; Knowlen, C.; Murakami, D.; Stonich, I.

    1990-01-01

    A new wall-mounted, magnetic detector is presented for measuring projectile passage times in tubes. The detector has the advantages of simplicity over laser and microwave techniques and has other advantages over the electrical contact wire technique. Representative data are presented. The detector is shown to be very insensitive to strong pressure waves and combustion, but able to detect the passage of the projectile (carrying one or two magnets) clearly. Two modes of operation of the detector are described and the use of these detectors to measure projectile velocities, accelerations, and spin rates is discussed.

  3. 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.

  4. Generation of Magnetohydrodynamic Waves in Low Solar Atmospheric Flux Tubes by Photospheric Motions

    NASA Astrophysics Data System (ADS)

    Mumford, S. J.; Fedun, V.; Erdélyi, R.

    2015-01-01

    Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions, small-scale magnetic flux tubes are generated via the interaction of granulation motion and the background magnetic field. This paper studies the effects of these motions on magnetohydrodynamic (MHD) wave excitation from broadband photospheric drivers. Numerical experiments of linear MHD wave propagation in a magnetic flux tube embedded in a realistic gravitationally stratified solar atmosphere between the photosphere and the low choromosphere (above β = 1) are performed. Horizontal and vertical velocity field drivers mimic granular buffeting and solar global oscillations. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers mimic observed torsional motions in the solar photosphere. The results are analyzed using a novel method for extracting the parallel, perpendicular, and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated to enable the quantification of the relative strengths of excited modes. The torsional drivers primarily excite Alfvén modes (≈60% of the total flux) with small contributions from the slow kink mode, and, for the logarithmic spiral driver, small amounts of slow sausage mode. The horizontal and vertical drivers primarily excite slow kink or fast sausage modes, respectively, with small variations dependent upon flux surface radius.

  5. GENERATION OF MAGNETOHYDRODYNAMIC WAVES IN LOW SOLAR ATMOSPHERIC FLUX TUBES BY PHOTOSPHERIC MOTIONS

    SciTech Connect

    Mumford, S. J.; Fedun, V.; Erdélyi, R.

    2015-01-20

    Recent ground- and space-based observations reveal the presence of small-scale motions between convection cells in the solar photosphere. In these regions, small-scale magnetic flux tubes are generated via the interaction of granulation motion and the background magnetic field. This paper studies the effects of these motions on magnetohydrodynamic (MHD) wave excitation from broadband photospheric drivers. Numerical experiments of linear MHD wave propagation in a magnetic flux tube embedded in a realistic gravitationally stratified solar atmosphere between the photosphere and the low choromosphere (above β = 1) are performed. Horizontal and vertical velocity field drivers mimic granular buffeting and solar global oscillations. A uniform torsional driver as well as Archimedean and logarithmic spiral drivers mimic observed torsional motions in the solar photosphere. The results are analyzed using a novel method for extracting the parallel, perpendicular, and azimuthal components of the perturbations, which caters to both the linear and non-linear cases. Employing this method yields the identification of the wave modes excited in the numerical simulations and enables a comparison of excited modes via velocity perturbations and wave energy flux. The wave energy flux distribution is calculated to enable the quantification of the relative strengths of excited modes. The torsional drivers primarily excite Alfvén modes (≈60% of the total flux) with small contributions from the slow kink mode, and, for the logarithmic spiral driver, small amounts of slow sausage mode. The horizontal and vertical drivers primarily excite slow kink or fast sausage modes, respectively, with small variations dependent upon flux surface radius.

  6. 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.

  7. Alfven waves in the solar atmosphere. III - Nonlinear waves on open flux tubes

    NASA Technical Reports Server (NTRS)

    Hollweg, J. V.; Jackson, S.; Galloway, D.

    1982-01-01

    Consideration is given the nonlinear propagation of Alfven waves on solar magnetic flux tubes, where the tubes are taken to be vertical, axisymmetric and initially untwisted and the Alfven waves are time-dependent axisymmetric twists. The propagation of the waves into the chromosphere and corona is investigated through the numerical solution of a set of nonlinear, time-dependent equations coupling the Alfven waves into motions that are parallel to the initial magnetic field. It is concluded that Alfven waves can steepen into fast shocks in the chromosphere, pass through the transition region to produce high-velocity pulses, and then enter the corona, which they heat. The transition region pulses have amplitudes of about 60 km/sec, and durations of a few tens of seconds. In addition, the Alfven waves exhibit a tendency to drive upward flows, with many of the properties of spicules.

  8. Maximum allowable heat flux for a submerged horizontal tube bundle

    SciTech Connect

    McEligot, D.M.

    1995-08-14

    For application to industrial heating of large pools by immersed heat exchangers, the socalled maximum allowable (or {open_quotes}critical{close_quotes}) heat flux is studied for unconfined tube bundles aligned horizontally in a pool without forced flow. In general, we are considering boiling after the pool reaches its saturation temperature rather than sub-cooled pool boiling which should occur during early stages of transient operation. A combination of literature review and simple approximate analysis has been used. To date our main conclusion is that estimates of q inch chf are highly uncertain for this configuration.

  9. 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

  10. Auroral electron precipitation and flux tube erosion in Titan’s upper atmosphere

    NASA Astrophysics Data System (ADS)

    Snowden, D.; Yelle, R. V.; Galand, M.; Coates, A. J.; Wellbrock, A.; Jones, G. H.; Lavvas, P.

    2013-09-01

    Cassini dasta shows that Titan’s atmosphere strongly depletes the electron content in Saturn’s flux tubes, producing features known as electron bite-outs, which indicate that the flux of auroral electrons decreases over time. To understand this process we have developed a time-dependent two-stream model, which uses field line geometries and drift paths calculated by a three-dimensional multi-fluid model of Titan’s plasma interaction. The boundary conditions of the model account for the time-dependent reduction or increase in electron flux along Saturn’s magnetic field lines because of the loss or production of electrons in Titan’s atmosphere. The modification of the auroral electron flux depends on the electron bounce period in Saturn’s outer magnetosphere; therefore, we also calculate electron bounce periods along several Kronian field lines accounting for both the magnetic mirroring force and the field-aligned electric potential in Saturn’s plasma sheet. We use the time-dependent two-stream model to calculate how the reduction in the auroral electron flux affects electron impact ionization and energy deposition rates in Titan’s upper atmosphere. We find that the flux of higher energy (>50 eV) electrons entering Titan’s atmosphere is strongly reduced over time, resulting in smaller ionization and energy deposition rates below ∼1300 km altitude. Finally, we show that sample spectrograms produced from our calculations are consistent with CAPS-ELS data.

  11. Dynamic Flux Tubes Form Reservoirs of Stability in Neuronal Circuits

    NASA Astrophysics Data System (ADS)

    Monteforte, Michael; Wolf, Fred

    2012-10-01

    Neurons in cerebral cortical circuits interact by sending and receiving electrical impulses called spikes. The ongoing spiking activity of cortical circuits is fundamental to many cognitive functions including sensory processing, working memory, and decision making. London et al. [Sensitivity to Perturbations In Vivo Implies High Noise and Suggests Rate Coding in Cortex, Nature (London)NATUAS0028-0836 466, 123 (2010).10.1038/nature09086] recently argued that even a single additional spike can cause a cascade of extra spikes that rapidly decorrelate the microstate of the network. Here, we show theoretically in a minimal model of cortical neuronal circuits that single-spike perturbations trigger only a very weak rate response. Nevertheless, single-spike perturbations are found to rapidly decorrelate the microstate of the network, although the dynamics is stable with respect to small perturbations. The coexistence of stable and unstable dynamics results from a system of exponentially separating dynamic flux tubes around stable trajectories in the network’s phase space. The radius of these flux tubes appears to decrease algebraically with neuron number N and connectivity K, which implies that the entropy of the circuit’s repertoire of state sequences scales as Nln⁡(KN).

  12. Fermionic vacuum polarization by an Abelian magnetic tube in the cosmic string spacetime

    NASA Astrophysics Data System (ADS)

    Maior de Sousa, M. S.; Ribeiro, R. F.; Bezerra de Mello, E. R.

    2017-02-01

    In this paper, we consider a charged massive fermionic quantum field in the idealized cosmic string spacetime and in the presence of a magnetic field confined in a cylindrical tube of finite radius. Three distinct configurations for the magnetic fields are taken into account: (i) a cylindrical shell of radius a , (ii) a magnetic field proportional to 1 /r , and (iii) a constant magnetic field. In these three cases, the axis of the infinitely long tube of radius a coincides with the cosmic string. Our main objectives in this paper are to analyze the fermionic condensate (FC) and the vacuum expectation value (VEV) of the fermionic energy-momentum tensor. In order to do that, we explicitly construct the complete set of normalized wave functions for each configuration of the magnetic field. We show that in the region outside the tube, the FC and the VEV of the energy-momentum tensor are decomposed into two parts: The first ones correspond to the zero-thickness magnetic flux contributions, and the second ones are induced by the nontrivial structure of the magnetic field, named core-induced contributions. The latter present specific forms depending on the magnetic field configuration considered. We also show that the VEV of the energy-momentum tensor is diagonal and obeys the conservation condition, and its trace is expressed in terms of the fermionic condensate. The zero-thickness contributions to the FC and VEV of the energy-momentum tensor depend only on the fractional part of the ration of the magnetic flux inside the tube by the quantum one. As to the core-induced contributions, they depend on the total magnetic flux inside the tube and, consequently, in general, are not a periodic function of the magnetic flux.

  13. 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.

  14. 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.

  15. ON THE DISPERSION AND SCATTERING OF MAGNETOHYDRODYNAMIC WAVES BY LONGITUDINALLY STRATIFIED FLUX TUBES

    SciTech Connect

    Andries, J.; Cally, P. S. E-mail: paul.cally@monash.edu

    2011-12-20

    We provide a fairly general analytic theory for the dispersion and scattering of magnetohydrodynamic waves by longitudinally stratified flux tubes. The theory provides a common framework for, and synthesis of, many previous studies of flux tube oscillations that were carried out under various simplifying assumptions. The present theory focuses on making only a minimal number of assumptions. As a result it thus provides an analytical treatment of several generalizations of existing tube oscillation models. The most important practical cases are inclusion of plasma pressure and possibly buoyancy effects in models of straight non-diverging tubes as applied in coronal seismology, and relaxation of the 'thin tube' approximation in oscillation models of diverging tubes as applied both in the context of p-mode scattering and coronal seismology. In particular, it illustrates the unifying theoretical framework underlying both the description of waves scattered by flux tubes and the dispersion of waves carried along flux tubes.

  16. Particle propagation, wave growth and energy dissipation in a flaring flux tube

    NASA Technical Reports Server (NTRS)

    White, S. M.; Melrose, D. B.; Dulk, G. A.

    1986-01-01

    Wave amplification by downgoing particles in a common flare model is investigated. The flare is assumed to occur at the top of a coronal magnetic flux loop, and results in the heating of plasma in the flaring region. The hot electrons propagate down the legs of the flux tube towards increasing magnetic field. It is simple to demonstrate that the velocity distributions which result in this model are unstable to both beam instabilities and cyclotron maser action. An explanation is presented for the propagation effects on the distribution, and the properties of the resulting amplified waves are explored, concentrating on cyclotron maser action, which has properties (emission in the z mode below the local gyrofrequency) quite different from maser action by other distributions considered in the context of solar flares. The z mode waves will be damped in the coronal plasma surrounding the flaring flux tube and lead to heating there. This process may be important in the overall energy budget of the flare. The downgoing maser is compared with the loss cone maser, which is more likely to produce observable bursts.

  17. Linear MHD Wave Propagation in Time-Dependent Flux Tube. II. Finite Plasma Beta

    NASA Astrophysics Data System (ADS)

    Williamson, A.; Erdélyi, R.

    2014-04-01

    The propagation of magnetohydrodynamic (MHD) waves is an area that has been thoroughly studied for idealised static and steady state magnetised plasma systems applied to numerous solar structures. By applying the generalisation of a temporally varying background density to an open magnetic flux tube, mimicking the observed slow evolution of such waveguides in the solar atmosphere, further investigations into the propagation of both fast and slow MHD waves can take place. The assumption of a zero-beta plasma (no gas pressure) was applied in Williamson and Erdélyi ( Solar Phys. 2013, doi:10.1007/s11207-013-0366-9, Paper I) is now relaxed for further analysis here. Firstly, the introduction of a finite thermal pressure to the magnetic flux tube equilibrium modifies the existence of fast MHD waves which are directly comparable to their counterparts found in Paper I. Further, as a direct consequence of the non-zero kinetic plasma pressure, a slow MHD wave now exists, and is investigated. Analysis of the slow wave shows that, similar to the fast MHD wave, wave amplitude amplification takes place in time and height. The evolution of the wave amplitude is determined here analytically. We conclude that for a temporally slowly decreasing background density both propagating magnetosonic wave modes are amplified for over-dense magnetic flux tubes. This information can be very practical and useful for future solar magneto-seismology applications in the study of the amplitude and frequency properties of MHD waveguides, e.g. for diagnostic purposes, present in the solar atmosphere.

  18. 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.

  19. 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.

  20. The 3D Structure of Flux Tubes That Admit Flute Instability in the Scrape-Off-Layer (SOL) of Tokamaks

    NASA Astrophysics Data System (ADS)

    Takahashi, Hironori

    2014-10-01

    A severe reduction in size down to an ion gyro-radius scale, commonly known as ``squeezing,'' in a lateral dimension of the cross section of a flux tube is traditionally thought to inhibit the occurrence of the flute instability in the Scrape-off-Layer of a diverted tokamak by isolating the main volume of the flux tube from its ends at electrically conducting target plates. A study reported here in the 3D flux tube structure reveals the absence of squeezing for a flux tube that is sufficiently large in its toroidal extent (small toroidal harmonic number n) and located in a layer of low field-line shear around the ``sweet spot'' (about mid-way between the primary and secondary separatrices). The low-shear layer does not hence inhibit the flute instability through the squeezing mechanism, and may thus restore the flute instability, among the most virulent in the magnetized plasma, to the ranks of candidate electrostatic instabilities thought to underlie the turbulence in the SOL in tokamaks. Variations along the flux tube of geometrical characteristics including the cross section will be calculated to develop criteria for the absence of squeezing. Supported in part by the US DOE under DE-AC02-09CH11466.

  1. Flux tube train model for local turbulence simulation of toroidal plasmas

    SciTech Connect

    Watanabe, T.-H.; Sugama, H.; Ishizawa, A.; Nunami, M.

    2015-02-15

    A new simulation method for local turbulence in toroidal plasmas is developed by extending the conventional idea of the flux tube model. In the new approach, a train of flux tubes is employed, where flux tube simulation boxes are serially connected at each end along a field line so as to preserve a symmetry of the local gyrokinetic equations for image modes in an axisymmetric torus. Validity of the flux tube train model is confirmed against the toroidal ion temperature gradient turbulence for a case with a long parallel correlation of fluctuations, demonstrating numerical advantages over the conventional method in the time step size and the symmetry-preserving property.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. TIME-DEPENDENT TURBULENT HEATING OF OPEN FLUX TUBES IN THE CHROMOSPHERE, CORONA, AND SOLAR WIND

    SciTech Connect

    Woolsey, L. N.; Cranmer, S. R.

    2015-10-01

    We investigate several key questions of plasma heating in open-field regions of the corona that connect to the solar wind. We present results for a model of Alfvén-wave-driven turbulence for three typical open magnetic field structures: a polar coronal hole, an open flux tube neighboring an equatorial streamer, and an open flux tube near a strong-field active region. We compare time-steady, one-dimensional turbulent heating models against fully time-dependent three-dimensional reduced-magnetohydrodynamic modeling of BRAID. We find that the time-steady results agree well with time-averaged results from BRAID. The time dependence allows us to investigate the variability of the magnetic fluctuations and of the heating in the corona. The high-frequency tail of the power spectrum of fluctuations forms a power law whose exponent varies with height, and we discuss the possible physical explanation for this behavior. The variability in the heating rate is bursty and nanoflare-like in nature, and we analyze the amount of energy lost via dissipative heating in transient events throughout the simulation. The average energy in these events is 10{sup 21.91} erg, within the “picoflare” range, and many events reach classical “nanoflare” energies. We also estimated the multithermal distribution of temperatures that would result from the heating-rate variability, and found good agreement with observed widths of coronal differential emission measure distributions. The results of the modeling presented in this paper provide compelling evidence that turbulent heating in the solar atmosphere by Alfvén waves accelerates the solar wind in open flux tubes.

  7. 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.

  8. 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.

  9. 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!

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. The Physics of Twisted Magnetic Tubes Rising in a Stratified Medium: Two-dimensional Results

    NASA Astrophysics Data System (ADS)

    Emonet, T.; Moreno-Insertis, F.

    1998-01-01

    The physics of a twisted magnetic flux tube rising in a stratified medium is studied using a numerical magnetohydrodynamic (MHD) code. The problem considered is fully compressible (has no Boussinesq approximation), includes ohmic resistivity, and is two-dimensional, i.e., there is no variation of the variables in the direction of the tube axis. We study a high-plasma β-case with a small ratio of radius to external pressure scale height. The results obtained will therefore be of relevance to understanding the transport of magnetic flux across the solar convection zone. We confirm that a sufficient twist of the field lines around the tube axis can suppress the conversion of the tube into two vortex rolls. For a tube with a relative density deficit on the order of 1/β (the classical Parker buoyancy) and a radius smaller than the pressure scale height (R2<tube with this degree of twist is studied in detail, including the initial transient phase, the internal torsional oscillations, and the asymptotic, quasi-stationary phase. During the initial phase, the outermost, weakly magnetized layers of the tube are torn off its main body and endowed with vorticity. They yield a trailing magnetized wake with two vortex rolls. The fraction of the total magnetic flux that is brought to the wake is a function of the initial degree of twist. In the weakly twisted case, most of the initial tube is turned into vortex rolls. With a strong initial twist, the tube rises with only a small deformation and no substantial loss of magnetic flux. The formation of the wake and the loss of flux from the main body of the tube are basically complete after the initial transient phase. A sharp interface between the tube interior and the external flows is formed at the tube front and sides; this area has the characteristic features of a magnetic boundary layer. Its

  16. 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.

  17. X-ray tube with magnetic electron steering

    DOEpatents

    Reed, Kim W.; Turman, Bobby N.; Kaye, Ronald J.; Schneider, Larry X.

    2000-01-01

    An X-ray tube uses a magnetic field to steer electrons. The magnetic field urges electrons toward the anode, increasing the proportion of electrons emitted from the cathode that reach desired portions of the anode and consequently contribute to X-ray production. The magnetic field also urges electrons reflected from the anode back to the anode, further increasing the efficiency of the tube.

  18. 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.

  19. 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

  20. Low thermal flux glass-fiber tubing for cryogenic service

    NASA Technical Reports Server (NTRS)

    Hall, C. A.; Spond, D. E.

    1977-01-01

    This paper describes analytical techniques, fabrication development, and test results for composite tubing that has many applications in aerospace and commercial cryogenic installations. Metal liner fabrication is discussed in detail with attention given to resistance-welded liners, fusion-welded liners, chem-milled tubing liners, joining tube liners and end fittings, heat treatment and leak checks. Composite overwrapping, a second method of tubing fabrication, is also discussed. Test programs and analytical correlation are considered along with composite tubing advantages such as minimum weight, thermal efficiency and safety and reliability.

  1. 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.

  2. A Low Cost Photo-Electric Detector for an Arched Flux Tube Experiment

    NASA Astrophysics Data System (ADS)

    Perkins, Rory; Bellan, Paul

    2008-11-01

    A low cost EUV detector is being developed for use in a laboratory experiment where two plasma-filled flux tubes merge in either a co-helicity or counter-helicity arrangement (J.F. Hansen, S.K.P. Tripathi, and P.M. Bellan, Phys. Plasma 2, 3177(2004)). The detector utilizes the photo-electric effect to measure EUV radiation from 10 to 120 nm (S.J. Zweben, R.J. Taylor, Plasma Physics, Vol. 23, No. 4(1981)). The detector geometry is coaxial. A cylindrical collimator capped in wire mesh was placed around the magnesium disk to collimate the field of view and reduce capacitive pick-up. Magnets placed outside the collimator deflect incoming charged particles. The detector was tested in a vacuum chamber with a flash lamp located 50 cm from the detector. A current-to-voltage amplifier with a 1 microsecond rise-time read the detector's output on the test chamber. The detector output on the main experimental chamber was sent directly into 50 ohms with no amplification and produced signals above 200 mV, well above the observed noise. The rise-time for this configuration is well below 1 microsecond. An array of such detectors is currently being designed to image the flux tubes in this EUV range.

  3. 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.

  4. 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.

  5. Magnetic field simulation of magnetic phase detection sensor for steam generator tube in nuclear power plants

    NASA Astrophysics Data System (ADS)

    Ryu, Kwon-sang; Son, Derac; Park, Duck-gun; Kim, Yong-il

    2010-05-01

    Magnetic phases and defects are partly produced in steam generator tubes by stress and heat, because steam generator tubes in nuclear power plants are used under high temperature, high pressure, and radioactivity. The magnetic phases induce an error in the detection of the defects in steam generator tubes by the conventional eddy current method. So a new method is needed for detecting the magnetic phases in the steam generator tubes. We designed a new U-type yoke which has two kinds of coils and simulated the signal by the magnetic phases and defects in the Inconnel 600 tube.

  6. Evidence from lattice data for a new particle on the worldsheet of the QCD flux tube.

    PubMed

    Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

    2013-08-09

    We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD flux tube--the worldsheet axion.

  7. The magnetic topology of the plasmoid flux rope in a MHD-simulation of magnetotail reconnection

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.

    On the basis of a 3D MHD simulation, the magnetic topology of a plasmoid that forms by a localized reconnection process in a magnetotail configuration (including a net dawn-dusk magnetic field component B sub y N is discussed. As a consequence of B sub y N not equalling 0, the plasmoid assumes a helical flux rope structure rather than an isolated island or bubble structure. Initially all field lines of the plasmoid flux rope remain connected with the earth, while at later times a gradually increasing amount of flux tubes becomes separated, connecting to either the distant boundary or to the flank boundaries. In this stage, topologically different flux tubes become tangled and wrapped around each other, consistent with predictions on the basis of an ad hoc plasmoid model.

  8. The magnetic topology of the plasmoid flux rope in a MHD-simulation of magnetotail reconnection

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.

    On the basis of a three-dimensional MHD simulation we discuss the magnetic topology of a plasmoid that forms by a localized reconnection process in a magnetotail configuration including a net dawn-dusk magnetic field component ByN. As a consequence of ByN ≠ 0 the plasmoid assumes a helical flux rope structure rather than an isolated island or bubble structure. Initially all field lines of the plasmoid flux rope remain connected with the Earth, while at later times a gradually increasing amount of flux tubes becomes separated, connecting to either the distant boundary or to the flank boundaries. In this stage topologically different flux tubes become tangled and wrapped around each other, consistent with predictions on the basis of an ad-hoc plasmoid model.

  9. The magnetic topology of the plasmoid flux rope in a MHD simulation of magnetotail reconnection

    NASA Astrophysics Data System (ADS)

    Birn, J.; Hesse, M.

    On the basis of a three-dimensional MHD simulation we discuss the magnetic topology of a plasmoid that forms by a localized reconnection process in a magnetotail configuration including a net dawn-dusk magnetic field component B sub yN. As a consequence of B sub yN ne 0 the plasmoid gets a helical flux rope structure rather than an isolated island or bubble structure. Initially all field lines of the plasmoid flux rope remain connected with the Earth, while at later times a gradually increasing number of flux tubes becomes separated, connecting to either the distant boundary or to the flank boundaries. In this stage topologically different flux tubes become tangled and wrapped around each other, consistent with predictions on the basis of ad hoc plasmoid models.

  10. The magnetic topology of the plasmoid flux rope in a MHD simulation of magnetotail reconnection

    SciTech Connect

    Birn, J.; Hesse, M.

    1989-01-01

    On the basis of a three-dimensional MHD simulation we discuss the magnetic topology of a plasmoid that forms by a localized reconnection process in a magnetotail configuration including a net dawn-dusk magnetic field component B/sub yN/. As a consequence of b/sub yN/ /ne/ 0 the plasmid gets a helical flux rope structure rather than an isolated island or bubble structure. Initially all field lines of the plasmid flux rope remain connected with the Earth, while at later times a gradually increasing amount of flux tubes becomes separated, connecting to either the distant boundary or to the flank boundaries. In this stage topologically different flux tubes become tangled and wrapped around each other, consistent with predictions on the basis of ad-hoc plasmid models. 10 refs., 8 figs.

  11. 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.

  12. Mean-field and direct numerical simulations of magnetic flux concentrations from vertical field

    NASA Astrophysics Data System (ADS)

    Brandenburg, A.; Gressel, O.; Jabbari, S.; Kleeorin, N.; Rogachevskii, I.

    2014-02-01

    Context. Strongly stratified hydromagnetic turbulence has previously been found to produce magnetic flux 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 magnetic pressure instability and have been able to reproduce many aspects of direct numerical simulations (DNS) regarding growth rate, shape of the resulting magnetic structures, and their height as a function of magnetic field strength. Unlike the case of an imposed horizontal field, for a vertical one, magnetic flux concentrations of equipartition strength with the turbulence can be reached, resulting in magnetic spots that are reminiscent of sunspots. Aims: We determine under what conditions magnetic flux 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 magnetic flux concentrations in forced isothermal turbulence with an imposed vertical magnetic 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 magnetic flux 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 magnetic structures are determined as functions of two input parameters characterizing the parameterization of the effective magnetic pressure. DNS, ILES, and MFS show magnetic flux tubes with mean-field energies comparable to the turbulent kinetic energy. These tubes can reach a length of about

  13. 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.

  14. Pool boiling of distilled water over tube bundle with variable heat flux

    NASA Astrophysics Data System (ADS)

    Swain, Abhilas; Mohanty, Rajiva Lochan; Das, Mihir Kumar

    2017-02-01

    The experimental investigation of saturated pool boiling heat transfer of distilled water over plain tube bundle, under uniform and varying heat flux condition along the height are presented in this article. Experiments are carried out under various heat flux configurations applied to rows of tube bundles and pitch distance to diameter ratios of 1.25, 1.6 and 1.95. The wall superheats and pool boiling heat transfer coefficients over individual rows are determined. The pool boiling heat transfer coefficients for variable heat flux and uniform heat flux conditions are compared. The results indicate that the bundle effect is found to exist for uniform as well as variable heat flux under all operating conditions in the present investigation. The variable heat flux resulted in range of wall superheat being highest for decreasing heat flux from bottom to top and lowest for increasing heat flux from bottom to top.

  15. 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

  16. Closed flux tubes in D = 2 + 1 SU( N ) gauge theories: dynamics and effective string description

    NASA Astrophysics Data System (ADS)

    Athenodorou, Andreas; Teper, Michael

    2016-10-01

    We extend our earlier calculations of the spectrum of closed flux tubes in SU( N ) gauge theories in 2 + 1 dimensions, with a focus on questions raised by recent theoretical progress on the effective string action of long flux tubes and the world-sheet action for flux tubes of moderate lengths. Our new calculations in SU(4) and SU(8) provide evidence that the leading O(1 /l γ ) non-universal correction to the flux tube ground state energy does indeed have a power γ ≥ 7. We perform a study in SU(2), where we can traverse the length at which the Nambu-Goto ground state becomes tachyonic, to obtain an all- N view of the spectrum. Our comparison of the k = 2 flux tube excitation energies in SU(4) and SU(6) suggests that the massive world sheet excitation associated with the k = 2 binding has a scale that knows about the group and hence the theory in the bulk, and we comment on the potential implications of world sheet massive modes for the bulk spectrum. We provide a quantitative analysis of the surprising (near-)orthogonality of flux tubes carrying flux in different SU( N ) representations, which implies that their screening by gluons is highly suppressed even at small N.

  17. Study of Permanent Magnet Focusing for Astronomical Camera Tubes

    NASA Technical Reports Server (NTRS)

    Long, D. C.; Lowrance, J. L.

    1975-01-01

    A design is developed of a permanent magnet assembly (PMA) useful as the magnetic focusing unit for the 35 and 70 mm (diagonal) format SEC tubes. Detailed PMA designs for both tubes are given, and all data on their magnetic configuration, size, weight, and structure of magnetic shields adequate to screen the camera tube from the earth's magnetic field are presented. A digital computer is used for the PMA design simulations, and the expected operational performance of the PMA is ascertained through the calculation of a series of photoelectron trajectories. A large volume where the magnetic field uniformity is greater than 0.5% appears obtainable, and the point spread function (PSF) and modulation transfer function(MTF) indicate nearly ideal performance. The MTF at 20 cycles per mm exceeds 90%. The weight and volume appear tractable for the large space telescope and ground based application.

  18. 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.

  19. 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.

  20. Simulations of emerging magnetic flux. II. The formation of unstable coronal flux ropes and the initiation of coronal mass ejections

    SciTech Connect

    Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.

    2014-05-20

    We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone flux tube into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface flux into the corona, a combination of vortical motions and internal magnetic reconnection forms a coronal flux 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 flux rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal flux rope axis, and the flux 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 flux 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 flux 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 'magnetic breakout', are operating during the emergence of new active regions.

  1. Simulations of Emerging Magnetic Flux. II. The Formation of Unstable Coronal Flux Ropes and the Initiation of Coronal Mass Ejections

    NASA Technical Reports Server (NTRS)

    Leake, James E.; Linton, Mark G.; Antiochos, Spiro K.

    2014-01-01

    We present results from three-dimensional magnetohydrodynamic simulations of the emergence of a twisted convection zone flux tube into a pre-existing coronal dipole field. As in previous simulations, following the partial emergence of the sub-surface flux into the corona, a combination of vortical motions and internal magnetic reconnection forms a coronal flux 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 flux rope into the corona. After sufficient expansion, internal reconnection occurs beneath the coronal flux rope axis, and the flux 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 flux 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 flux 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 "magnetic breakout," are operating during the emergence of new active regions.

  2. THE BEHAVIOR OF TRANSVERSE WAVES IN NONUNIFORM SOLAR FLUX TUBES. I. COMPARISON OF IDEAL AND RESISTIVE RESULTS

    SciTech Connect

    Soler, Roberto; Terradas, Jaume; Oliver, Ramón; Goossens, Marcel

    2013-11-10

    Magnetohydrodynamic (MHD) waves are ubiquitously observed in the solar atmosphere. Kink waves are a type of transverse MHD waves in magnetic flux tubes that are damped due to resonant absorption. The theoretical study of kink MHD waves in solar flux tubes is usually based on the simplification that the transverse variation of density is confined to a nonuniform layer much thinner than the radius of the tube, i.e., the so-called thin boundary approximation. Here, we develop a general analytic method to compute the dispersion relation and the eigenfunctions of ideal MHD waves in pressureless flux tubes with transversely nonuniform layers of arbitrary thickness. Results for kink waves are produced and compared with fully numerical resistive MHD eigenvalue computations in the limit of small resistivity. We find that the frequency and resonant damping rate are the same in both ideal and resistive cases. The actual results for thick nonuniform layers deviate from the behavior predicted in the thin boundary approximation and strongly depend on the shape of the nonuniform layer. The eigenfunctions in ideal MHD are very different from those in resistive MHD. The ideal eigenfunctions display a global character regardless of the thickness of the nonuniform layer, while the resistive eigenfunctions are localized around the resonance and are indistinguishable from those of ordinary resistive Alfvén modes. Consequently, the spatial distribution of wave energy in the ideal and resistive cases is dramatically different. This poses a fundamental theoretical problem with clear observational consequences.

  3. 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.

  4. Magnetic stabilization and vorticity in submillimeter paramagnetic liquid tubes

    PubMed Central

    Coey, J. Michael D.; Aogaki, Ryoichi; Byrne, Fiona; Stamenov, Plamen

    2009-01-01

    It is possible to suppress convection and dispersion of a paramagnetic liquid by means of a magnetic field. A tube of paramagnetic liquid can be stabilized in water along a ferromagnetic track in a vertical magnetic field, but not in a horizontal field. Conversely, an “antitube” of water can be stabilized in a paramagnetic liquid along the same track in a transverse horizontal field, but not in a vertical field. The stability arises from the interaction of the induced moment in the solution with the magnetic field gradient in the vicinity of the track. The magnetic force causes the tube of paramagnetic liquid to behave as if it were encased by an elastic membrane whose cross-section is modified by gravitational forces and Maxwell stress. Convection from the tube to its surroundings is inhibited, but not diffusion. Liquid motion within the paramagnetic tube, however, exhibits vorticity in tubes of diameter 1 mm or less—conditions where classical pipe flow would be perfectly streamline, and mixing extremely slow. The liquid tube is found to slide along the track almost without friction. Paramagnetic liquid tubes and antitubes offer appealing new prospects for mass transport, microfluidics, and electrodeposition. PMID:19416873

  5. Magnetic stabilization and vorticity in submillimeter paramagnetic liquid tubes.

    PubMed

    Coey, J Michael D; Aogaki, Ryoichi; Byrne, Fiona; Stamenov, Plamen

    2009-06-02

    It is possible to suppress convection and dispersion of a paramagnetic liquid by means of a magnetic field. A tube of paramagnetic liquid can be stabilized in water along a ferromagnetic track in a vertical magnetic field, but not in a horizontal field. Conversely, an "antitube" of water can be stabilized in a paramagnetic liquid along the same track in a transverse horizontal field, but not in a vertical field. The stability arises from the interaction of the induced moment in the solution with the magnetic field gradient in the vicinity of the track. The magnetic force causes the tube of paramagnetic liquid to behave as if it were encased by an elastic membrane whose cross-section is modified by gravitational forces and Maxwell stress. Convection from the tube to its surroundings is inhibited, but not diffusion. Liquid motion within the paramagnetic tube, however, exhibits vorticity in tubes of diameter 1 mm or less--conditions where classical pipe flow would be perfectly streamline, and mixing extremely slow. The liquid tube is found to slide along the track almost without friction. Paramagnetic liquid tubes and antitubes offer appealing new prospects for mass transport, microfluidics, and electrodeposition.

  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

    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.

  8. 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.

  9. 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.

  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. 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.

  12. 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.

  13. Current sheet formation in quasi-separatrix layers and hyperbolic flux tubes

    NASA Astrophysics Data System (ADS)

    Aulanier, G.; Pariat, E.; Démoulin, P.

    2005-12-01

    In 3D magnetic field configurations, quasi-separatrix layers (QSLs) are defined as volumes in which field lines locally display strong gradients of connectivity. Considering QSLs both as the preferential locations for current sheet development and magnetic reconnection, in general, and as a natural model for solar flares and coronal heating, in particular, has been strongly debated issues over the past decade. In this paper, we perform zero-β resistive MHD simulations of the development of electric currents in smooth magnetic configurations which are, strictly speaking, bipolar though they are formed by four flux concentrations, and whose potential fields contain QSLs. The configurations are driven by smooth and large-scale sub-Alfvénic footpoint motions. Extended electric currents form naturally in the configurations, which evolve through a sequence of quasi non-linear force-free equilibria. Narrow current layers also develop. They spontaneously form at small scales all around the QSLs, whatever the footpoint motions are. For long enough motions, the strongest currents develop where the QSLs are the thinnest, namely at the Hyperbolic Flux Tube (HFT), which generalizes the concept of separator. These currents progressively take the shape of an elongated sheet, whose formation is associated with a gradual steepening of the magnetic field gradients over tens of Alfvén times, due to the different motions applied to the field lines which pass on each side of the HFT. Our model then self-consistently accounts for the long-duration energy storage prior to a flare, followed by a switch-on of reconnection when the currents reach the dissipative scale at the HFT. In configurations whose potential fields contain broader QSLs, when the magnetic field gradients reach the dissipative scale, the currents at the HFT reach higher magnitudes. This implies that major solar flares which are not related to an early large-scale ideal instability, must occur in regions whose

  14. Signatures of Flux Tube Fragmentation and Strangeness Correlations in pp Collisions

    NASA Astrophysics Data System (ADS)

    Wong, Cheuk-Yin

    2017-01-01

    In the fragmentation of a color flux tube in high-energy pp collisions or e +-e‑ annihilations, the production of pairs along a color flux tube precedes the fragmentation of the tube. The local conservation laws in the production of these pairs will lead to the correlations of adjacently produced hadrons. As a consequence, the fragmentation of a flux tube will yield a many-hadron correlation in the form of a chain of hadrons ordered in rapidity, with adjacent hadrons correlated in charges, flavor contents, and azimuthal angles. It will also lead to a two-hadron angular correlation between two hadrons with opposite charges or strangeness that is suppressed at Δϕ ~ 0 but enhanced at Δϕ ~ π, within a rapidity window Δy~1/(dN/dy).

  15. Evidence from Lattice Data for a New Particle on the Worldsheet of the QCD Flux Tube

    NASA Astrophysics Data System (ADS)

    Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

    2013-08-01

    We propose a new approach for the calculation of the spectrum of excitations of QCD flux tubes. It relies on the fact that the worldsheet theory is integrable at low energies. With this approach, energy levels can be calculated for much shorter flux tubes than was previously possible, allowing for a quantitative comparison with existing lattice data. The improved theoretical control makes it manifest that existing lattice data provides strong evidence for a new pseudoscalar particle localized on the QCD flux tube—the worldsheet axion.

  16. 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.

  17. Stability of cool flux tubes in the solar chromosphere. II - Non-linear dynamical behaviour

    NASA Astrophysics Data System (ADS)

    Hassan, S. S.; Kneer, F.

    1990-06-01

    A single vertical cool flux tube in the solar chromosphere is focused upon for stability studies. The analysis of a previous study by Hasan and Kneer (1986) is extended to the nonlinear regime with a view to examining the consequences of having self-exciting mechanisms of oscillations above the photosphere. In particular, the possibility of whether the motions driven by the convective instability caused by the presence of CO could extract sufficient energy from the radiation field near the Tmin region of empirical models and deposit it in higher layers to produce chromospheric heating is investigated. The time evolution of this instability is followed by solving the MHD equations in the thin flux tube approximation. The analysis includes energy exchange with the radiation field. The simulations of a flux tube with a transmitting upper boundary show that the average energy flux in the oscillations is inadequate for chromospheric heating.

  18. 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.

  19. MAGNETOHYDRODYNAMIC KINK WAVES IN NONUNIFORM SOLAR FLUX TUBES: PHASE MIXING AND ENERGY CASCADE TO SMALL SCALES

    SciTech Connect

    Soler, Roberto; Terradas, Jaume

    2015-04-10

    Magnetohydrodynamic (MHD) kink waves are ubiquitously observed in the solar atmosphere. The propagation and damping of these waves may play relevant roles in the transport and dissipation of energy in the solar atmospheric medium. However, in the atmospheric plasma dissipation of transverse MHD wave energy by viscosity or resistivity needs very small spatial scales to be efficient. Here, we theoretically investigate the generation of small scales in nonuniform solar magnetic flux tubes due to phase mixing of MHD kink waves. We go beyond the usual approach based on the existence of a global quasi-mode that is damped in time due to resonant absorption. Instead, we use a modal expansion to express the MHD kink wave as a superposition of Alfvén continuum modes that are phase mixed as time evolves. The comparison of the two techniques evidences that the modal analysis is more physically transparent and describes both the damping of global kink motions and the building up of small scales due to phase mixing. In addition, we discuss that the processes of resonant absorption and phase mixing are closely linked. They represent two aspects of the same underlying physical mechanism: the energy cascade from large scales to small scales due to naturally occurring plasma and/or magnetic field inhomogeneities. This process may provide the necessary scenario for efficient dissipation of transverse MHD wave energy in the solar atmospheric plasma.

  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. 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.

  2. Dynamical fragmentation of flux tubes in the Friedberg-Lee model

    NASA Astrophysics Data System (ADS)

    Loh, S.; Greiner, C.; Mosel, U.; Thoma, M. H.

    1997-02-01

    We present two novel dynamical features of flux tubes in the Friedberg-Lee model. First the fusion of two (anti-)parallel flux tubes, where we extract a string-string interaction potential which has a qualitative similarity to the nucleon-nucleon potential in the Friedberg-Lee model obtained by Koepf et al. Furthermore we show the dynamical breakup of flux tubes via q overlineq- particle production and the disintegration into mesons. We find, as a shortcoming of the present realization of the model, that the full dynamical transport approach presented in a previous publication fails to provide the disintegration mechanism in the semiclassical limit. Therefore, in addition, we present here a molecular dynamical approach for the motion of the quarks and show, as a first application, the space-time development of the wuarks and their mean-fields for Lund-type string fragmentation processes.

  3. Flux tubes and the type-I/type-II transition in a superconductor coupled to a superfluid

    SciTech Connect

    Alford, Mark G.; Good, Gerald

    2008-07-01

    We analyze magnetic-flux tubes at zero temperature in a superconductor that is coupled to a superfluid via both density and gradient ('entrainment') interactions. The example we have in mind is high-density nuclear matter, which is a proton superconductor and a neutron superfluid, but our treatment is general and simple, modeling the interactions as a Ginzburg-Landau effective theory with four-fermion couplings, including only s-wave pairing. We numerically solve the field equations for flux tubes with an arbitrary number of flux quanta and compare their energies. This allows us to map the type-I/type-II transition in the superconductor, which occurs at the conventional {kappa}{identical_to}{lambda}/{xi}=1/{radical}(2) if the condensates are uncoupled. We find that a density coupling between the condensates raises the critical {kappa} and, for a sufficiently high neutron density, resolves the type-I/type-II transition line into an infinite number of bands corresponding to 'type-II(n)' phases, in which n, the number of quanta in the favored flux tube, steps from 1 to infinity. For lower neutron density, the coupling creates spinodal regions around the type-I/type-II boundary, in which metastable flux configurations are possible. We find that a gradient coupling between the condensates lowers the critical {kappa} and creates spinodal regions. These exotic phenomena may not occur in nuclear matter, which is thought to be deep in the type-II region but might be observed in condensed-matter systems.

  4. 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.

  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. Compact Toroid Propagation in a Magnetized Drift Tube

    NASA Astrophysics Data System (ADS)

    Horton, Robert D.; Baker, Kevin L.; Hwang, David Q.; Evans, Russell W.

    2000-10-01

    Injection of a spheromak-like compact toroid (SCT) plasma into a toroidal plasma confinement device may require the SCT to propagate through a drift tube region occupied by a pre-existing magnetic field. This field is expected to extert a retarding force on the SCT, but may also result in a beneficial compression. The effects of transverse and longitudinal magnetic fields will be measured using the CTIX compact-toroid injector, together with a fast framing camera with an axial view of the formation, coaxial, and drift-tube regions. In the case of longitudinal magnetic field, comparisons will be made with the predictions of two-dimensional numerical simulation. The use of localized magnetic field to reduce plasma bridging of the insulating gap will also be investigated.

  7. UBIQUITOUS SOLAR ERUPTIONS DRIVEN BY MAGNETIZED VORTEX TUBES

    SciTech Connect

    Kitiashvili, I. N.; Kosovichev, A. G.; Lele, S. K.; Mansour, N. N.; Wray, A. A.

    2013-06-10

    The solar surface is covered by high-speed jets transporting mass and energy into the solar corona and feeding the solar wind. The most prominent of these jets have been known as spicules. However, the mechanism initiating these eruption events is still unknown. Using realistic numerical simulations we find that small-scale eruptions are produced by ubiquitous magnetized vortex tubes generated by the Sun's turbulent convection in subsurface layers. The swirling vortex tubes (resembling tornadoes) penetrate into the solar atmosphere, capture and stretch background magnetic field, and push the surrounding material up, generating shocks. Our simulations reveal complicated high-speed flow patterns and thermodynamic and magnetic structure in the erupting vortex tubes. The main new results are: (1) the eruptions are initiated in the subsurface layers and are driven by high-pressure gradients in the subphotosphere and photosphere and by the Lorentz force in the higher atmosphere layers; (2) the fluctuations in the vortex tubes penetrating into the chromosphere are quasi-periodic with a characteristic period of 2-5 minutes; and (3) the eruptions are highly non-uniform: the flows are predominantly downward in the vortex tube cores and upward in their surroundings; the plasma density and temperature vary significantly across the eruptions.

  8. Measurements and computations of mass flow and momentum flux through short tubes in rarefied gases

    NASA Astrophysics Data System (ADS)

    Lilly, T. C.; Gimelshein, S. F.; Ketsdever, A. D.; Markelov, G. N.

    2006-09-01

    Gas flows through orifices and short tubes have been extensively studied from the 1960s through the 1980s for both fundamental and practical reasons. These flows are a basic and often important element of various modern gas driven instruments. Recent advances in micro- and nanoscale technologies have paved the way for a generation of miniaturized devices in various application areas, from clinical analyses to biochemical detection to aerospace propulsion. The latter is the main area of interest of this study, where rarefied gas flow into a vacuum through short tubes with thickness-to-diameter ratios varying from 0.015 to 1.2 is investigated both experimentally and numerically with kinetic and continuum approaches. Helium and nitrogen gases are used in the range of Reynolds numbers from 0.02 to 770 (based on the tube diameter), corresponding to Knudsen numbers from 40 down to about 0.001. Propulsion properties of relatively thin and thick tubes are examined. Good agreement between experimental and numerical results is observed for mass flow rate and momentum flux, the latter being corrected for the experimental facility background pressure. For thick-to-thin tube ratios of mass flow and momentum flux versus pressure, a minimum is observed at a Knudsen number of about 0.5. A short tube propulsion efficiency is shown to be much higher than that of a thin orifice. The effect of surface specularity on a thicker tube specific impulse was found to be relatively small.

  9. ERUPTING FILAMENTS WITH LARGE ENCLOSING FLUX TUBES AS SOURCES OF HIGH-MASS THREE-PART CMEs, AND ERUPTING FILAMENTS IN THE ABSENCE OF ENCLOSING FLUX TUBES AS SOURCES OF LOW-MASS UNSTRUCTURED CMEs

    SciTech Connect

    Hutton, Joe; Morgan, Huw

    2015-11-01

    The 3-part appearance of many coronal mass ejections (CMEs) arising from erupting filaments emerges from a large magnetic flux tube structure, consistent with the form of the erupting filament system. Other CMEs arising from erupting filaments lack a clear 3-part structure and reasons for this have not been researched in detail. This paper aims to further establish the link between CME structure and the structure of the erupting filament system and to investigate whether CMEs which lack a 3-part structure have different eruption characteristics. A survey is made of 221 near-limb filament eruptions observed from 2013 May 03 to 2014 June 30 by Extreme UltraViolet (EUV) imagers and coronagraphs. Ninety-two filament eruptions are associated with 3-part structured CMEs, 41 eruptions are associated with unstructured CMEs. The remaining 88 are categorized as failed eruptions. For 34% of the 3-part CMEs, processing applied to EUV images reveals the erupting front edge is a pre-existing loop structure surrounding the filament, which subsequently erupts with the filament to form the leading bright front edge of the CME. This connection is confirmed by a flux-rope density model. Furthermore, the unstructured CMEs have a narrower distribution of mass compared to structured CMEs, with total mass comparable to the mass of 3-part CME cores. This study supports the interpretation of 3-part CME leading fronts as the outer boundaries of a large pre-existing flux tube. Unstructured (non 3-part) CMEs are a different family to structured CMEs, arising from the eruption of filaments which are compact flux tubes in the absence of a large system of enclosing closed field.

  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. Comparisons of Earthward Poynting flux and the kinetic energy flux of up-flowing transversely heated ions from the Polar spacecraft on cusp magnetic field lines

    NASA Astrophysics Data System (ADS)

    Tian, S.; Wygant, J. R.; Cattell, C. A.; Scudder, J. D.; Mozer, F.; Russell, C. T.

    2013-12-01

    This paper presents estimates of the Poynting flux flowing along magnetic field lines in the Earth's cusp region over altitudes from 0.8 Re to 7 Re using measurements during several passes from the Polar spacecraft. The Poynting flux is calculated from measurements of electric fields from the University of California, Berkeley double probe electric field instrument, and from magnetic field measurements from the U.C.L.A. fluxgate magnetometer. The estimates of Poynting flux are of special interest because the high altitude mapping of the cusp magnetic flux tubes may connect to newly reconnected field lines and the low altitude mapping of these field lines is the scene of powerful acceleration processes, most notably transverse heating and outflow of ions. The data show that the Poynting flux is predominantly downward over the frequency range from 1 mHz to 1 Hz . This frequency range includes the Poynting flux due to steady state convection and field-aligned current systems, Alfven waves, and kinetic Alfven waves. Measurement of transversely heated ions over the energy ranges from 10 eV to several keV and their associated ion kinetic energy flux are presented from the University of Iowa Hydra instrument and compared to the values of the downward Poynting flux. Generally the downward Poynting flux exceeds the upward kinetic energy flux of the ions.

  12. 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.

  13. From QCD Flux Tubes to Gravitational S-matrix and Back

    NASA Astrophysics Data System (ADS)

    Gorbenko, Victor

    We study the effective field theory of long relativistic strings such as confining flux tubes in QCD. Our main focus is on the scattering matrix of massless exci- tations propagating on the string’s worldsheet. The Lorentz invariance of QCD manifests itself in certain soft theorems satisfied by the amplitudes. We find that critical dimension appears as a condition that allows this scattering to be inte- grable and consequently flux tubes in four-dimensional QCD do not fall into this category. In case of the critical dimension equal to 26, however, we are able to find a full integrable S-matrix that exhibits many features expected from gravi- tational models. Moreover, it gives rise to a family of not necessarily integrable two-dimensional theories that inherit very peculiar UV-properties. We discuss im- plication of this construction for the hierarchy problem. We then return to the QCD flux tubes and find that integrability-inspired techniques can be applied to them in an approximate way that allows us to calculate their spectrum in the regime inaccessible for standard perturbation theory. In particular, analysis of the lattice data allows us to identify the first massive particle present on the world sheet of the QCD flux tube.

  14. Magnetic field effect on flow parameters of blood along with magnetic particles in a cylindrical tube

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    In this paper, the effect of external uniform magnetic field on flow parameters of both blood and magnetic particles is reported through a mathematical model using magnetohydrodynamics (MHD) approach. The fluid is acted upon by a varying pressure gradient and an external uniform magnetic field is applied perpendicular to the cylindrical tube. The governing nonlinear partial differential equations were solved numerically and found that flow parameters are affected by the influence of magnetic field. Further, artificial blood (75% water+25% Glycerol) along with iron oxide magnetic particles were prepared and transported into a glass tube with help of a peristaltic pump. The velocity of artificial blood along with magnetic particles was experimentally measured at different magnetic fields ranging from 100 to 600 mT. The model results show that the velocity of blood and magnetic particles is appreciably reduced under the influence of magnetic field, which is supported by our experimental results.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. DEVELOPMENT OF S-BAND LOW-NOISE PERIODIC PERMANENT MAGNETIC TRAVELING-WAVE TUBE

    DTIC Science & Technology

    MICROWAVE AMPLIFIERS, *TRAVELING WAVE TUBES, ANODES, DESIGN, ELECTRON BEAMS, ELECTRON GUNS, FOCUSING , HELIXES, IMPEDANCE MATCHING, MAGNETIC FIELDS, MAGNETS, NOISE (RADIO), REDUCTION, S BAND, STANDING WAVE RATIOS

  20. Correlation of critical heat flux data for uniform tubes

    SciTech Connect

    Jafri, T.; Dougherty, T.J.; Yang, B.W.

    1995-09-01

    A data base of more than 10,000 critical heat flux (CHF) data points has been compiled and analyzed. Two regimes of CHF are observed which will be referred to as the high CHF regime and the low CHF regime. In the high CHF regime, for pressures less than 110 bar, CHF (q{sub c}) is a determined by local conditions and is adequately represented by q{sub c} = (1.2/D{sup 1/2}) exp[-{gamma}(GX{sub t}){sup 1/2}] where the parameter {gamma} is an increasing function of pressure only, X{sub t} the true mass fraction of steam, and all units are metric but the heat flux is in MWm{sup -2}. A simple kinetic model has been developed to estimate X{sub t} as a function of G, X, X{sub i}, and X{sub O}, where X{sub i} is the inlet quality and X{sub O} represents the quality at the Onset of Significant Vaporization (OSV) which is estimated from the Saha-Zuber (S-Z) correlation. The model is based on a rate equation for vaporization suggested by, and consistent with, the S-Z correlation and contains no adjustable parameters. When X{sub i}X{sub O}, X{sub t} depends on X{sub i}, a nonlocal variable, and, in this case, CHF, although determined by local conditions, obeys a nonlocal correlation. This model appears to be satisfactory for pressures less than 110 bar, where the S-Z correlation is known to be reliable. Above 110 bar the method of calculating X{sub O}, and consequently X{sub t}, appears to fail, so this approach can not be applied to high pressure CHF data. Above 35 bar, the bulk of the available data lies in the high CHF regime while, at pressures less than 35 bar, almost all of the available data lie in the low CHF regime and appear to be nonlocal.

  1. 3D Laboratory Measurements of Forces, Flows, and Collimation in Arched Flux Tubes

    NASA Astrophysics Data System (ADS)

    Haw, Magnus; Bellan, Paul

    2016-10-01

    Fully 3D, vector MHD force measurements from an arched, current carrying flux tube (flux rope) are presented. The experiment consists of two arched plasma-filled flux ropes each powered by a capacitor bank. The two loops are partially overlapped, as in a Venn diagram, and collide and reconnect during their evolution. B-field data is taken on the lower plasma arch using a 54 channel B-dot probe. 3D volumetric data is acquired by placing the probe at 2700 locations and taking 5 plasma shots at each location. The resulting data set gives high resolution (2cm, 10ns) volumetric B-field data with high reproducibility (deviation of 3% between shots). Taking the curl of the measured 3D B-field gives current densities (J) in good agreement with measured capacitor bank current. The JxB forces calculated from the data have a strong axial component at the base of the current channel and are shown to scale linearly with axial gradients in current density. Assuming force balance in the flux tube minor radius direction, we infer near-Alfvenic axial flows from the footpoint regions which are consistent with the measured axial forces. Flux tube collimation is observed in conjunction with these axial flows. These dynamic processes are relevant to the stability and dynamics of coronal loops. Supported provided by NSF, AFOSR.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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

    the direction of the tube axis and thus, given the twist of the magnetic tube, almost anti-parallel to the field lines at the upper boundary of the rising plasma ball. A thin, dome-shaped current layer is formed at the interface between the two flux systems, in which ohmic dissipation and heating are taking place. The reconnection proceeds by merging successive layers on both sides of the reconnection site; however, this occurs not only at the cusp of the interface, but, also, gradually along its sides in the direction transverse to the ambient magnetic field. The topology of the magnetic field in the atmosphere is thereby modified: the reconnected field lines typically are part of the flanks of the tube below the photosphere but then join the ambient field system in the corona and reach the boundaries of the domain as horizontal field lines.

  11. Numerical simulation of small-scale low- β magnetic flux ropes in the upper ionospheres of Venus and Mars

    NASA Astrophysics Data System (ADS)

    Shimazu, Hironori; Tanaka, Motohiko

    2008-10-01

    We use a three-dimensional macro-particle code (implicit-particle simulation) to examine the evolution of a small magnetic flux rope, where "small" means that its radius is close to the kinetic length scale of protons or electrons. Small flux ropes have been observed in the dayside ionospheres of Venus and Mars. In our simulations, we assume that the initial low- β force-free flux rope is maintained by the electron current: an electron beam flows in the flux rope along the magnetic field lines. The simulation results show that electrostatic two-stream (Buneman) instability is generated around the flux rope axis where the velocity of the electron beam is higher than the electron thermal velocity or the acoustic velocity. Electrons there are heated considerably in the direction parallel to the magnetic field by the instability, and an electron hot tube is formed. The magnetic field deviates from the initial force-free field although the helical structure of the magnetic field is maintained. These results indicate that the electron hot tubes will be evidence of flux rope formation in the low- β region, i.e., in the interaction region between the solar wind and the ionosphere, if they are found by high-resolution observations in the upper ionosphere.

  12. Quantized Chiral Magnetic Current from Reconnections of Magnetic Flux

    DOE PAGES

    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. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Surprisingly low frequency attenuation effects in long tubes when measuring turbulent fluxes at tall towers

    NASA Astrophysics Data System (ADS)

    Ibrom, Andreas; Brændholt, Andreas; Pilegaard, Kim

    2016-04-01

    The eddy covariance technique relies on the fast and accurate measurement of gas concentration fluctuations. While for some gasses robust and compact sensors are available, measurement of, e.g., non CO2 greenhouse gas fluxes is often performed with sensitive equipment that cannot be run on a tower without massively disturbing the wind field. To measure CO and N2O fluxes, we installed an eddy covariance system at a 125 m mast, where the gas analyser was kept in a laboratory close to the tower and the sampling was performed using a 150 m long tube with a gas intake at 96 m height. We investigated the frequency attenuation and the time lag of the N2O and CO concentration measurements with a concentration step experiment. The results showed surprisingly high cut-off frequencies (close to 2 Hz) and small low-pass filter induced time lags (< 0.3 s), which were similar for CO and N2O. The results indicate that the concentration signal was hardly biased during the ca 10 s travel through the tube. Due to the larger turbulence time scales at large measurement heights the low-pass correction was for the majority of the measurements < 5%. For water vapour the tube attenuation was massive, which had, however, a positive effect by reducing both the water vapour dilution correction and the cross sensitivity effects on the N2O and CO flux measurements. Here we present the set-up of the concentration step change experiment and its results and compare them with recently developed theories for the behaviour of gases in turbulent tube flows.

  20. Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

    1998-01-01

    Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

  1. Formation of sunspots and active regions through the emergence of magnetic flux generated in a solar convective dynamo

    NASA Astrophysics Data System (ADS)

    Chen, Feng; Rempel, Matthias D.; Fan, Yuhong

    2016-05-01

    We present a realistic numerical model of sunspot and active region formation through the emergence of flux tubes generated in a solar convective dynamo. The magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation are used as a time-dependent bottom boundary to drive the near surface layer radiation MHD simulations of magneto-convection and flux emergence with the MURaM code. The latter code simulates the emergence of the flux tubes through the upper most layer of the convection zone to the photosphere.The emerging flux tubes interact with the convection and break into small scale magnetic elements that further rise to the photosphere. At the photosphere, several bipolar pairs of sunspots are formed through the coalescence of the small scale magnetic elements. The sunspot pairs in the simulation successfully reproduce the fundamental observed properties of solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of the bipolar pairs. These asymmetries come most probably from the intrinsic asymmetries in the emerging fields imposed at the bottom boundary, where the horizontal fields are already tilted and the leading sides of the emerging flux tubes are usually up against the downdraft lanes of the giant cells. It is also found that penumbrae with numerous filamentary structures form in regions of strong horizontal magnetic fields that naturally comes from the ongoing flux emergence. In contrast to previous models, the penumbrae and umbrae are divided by very sharp boarders, which is highly consistent with observations.

  2. On the possibility for laboratory simulation of generation of Alfven disturbances in magnetic tubes in the solar atmosphere

    NASA Astrophysics Data System (ADS)

    Prokopov, Pavel; Zaharov, Yuriy; Tishchenko, Vladimir; Boyarintsev, Eduard; Melehov, Aleksandr; Ponomarenko, Arnold; Posuh, Vitaliy; Shayhislamov, Ildar

    2016-03-01

    The paper deals with generation of Alfven plasma disturbances in magnetic flux tubes through exploding laser plasma in magnetized background plasma. Processes with similar effect of excitation of torsion-type waves seem to provide energy transfer from the solar photosphere to corona. The studies were carried out at experimental stand KI-1 represented a high-vacuum chamber of 1.2 m diameter, 5 m long, external magnetic field up to 500 Gs along the chamber axis, and up to 2×10^-6 Torr pressure in operating mode. Laser plasma was produced when focusing the CO2 laser pulse on a flat polyethylene target, and then the laser plasma propagated in θ-pinch background hydrogen (or helium) plasma. As a result, the magnetic flux tube of 15-20 cm radius was experimentally simulated along the chamber axis and the external magnetic field direction. Also, the plasma density distribution in the tube was measured. Alfven wave propagation along the magnetic field was registered from disturbance of the magnetic field transverse component B_ψ and field-aligned current J_z. The disturbances propagate at near-Alfven velocity of 70-90 km/s and they are of left-hand circular polarization of the transverse component of magnetic field. Presumably, Alfven wave is generated by the magnetic laminar mechanism of collisionless interaction between laser plasma cloud and background. The right-hand polarized high-frequency whistler predictor was registered which have been propagating before Alfven wave at 300 km/s velocity. The polarization direction changed with Alfven wave coming. Features of a slow magnetosonic wave as a sudden change in background plasma concentration along with simultaneous displacement of the external magnetic field were found. The disturbance propagates at ~20-30 km/s velocity, which is close to that of ion sound at low plasma beta value. From preliminary estimates, the disturbance transfers about 10 % of the original energy of laser plasma.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  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. Sabots, Obturator and Gas-In-Launch Tube Techniques for Heat Flux Models in Ballistic Ranges

    NASA Technical Reports Server (NTRS)

    Bogdanoff, David W.; Wilder, Michael C.

    2013-01-01

    For thermal protection system (heat shield) design for space vehicle entry into earth and other planetary atmospheres, it is essential to know the augmentation of the heat flux due to vehicle surface roughness. At the NASA Ames Hypervelocity Free Flight Aerodynamic Facility (HFFAF) ballistic range, a campaign of heat flux studies on rough models, using infrared camera techniques, has been initiated. Several phenomena can interfere with obtaining good heat flux data when using this measuring technique. These include leakage of the hot drive gas in the gun barrel through joints in the sabot (model carrier) to create spurious thermal imprints on the model forebody, deposition of sabot material on the model forebody, thereby changing the thermal properties of the model surface and unknown in-barrel heating of the model. This report presents developments in launch techniques to greatly reduce or eliminate these problems. The techniques include the use of obturator cups behind the launch package, enclosed versus open front sabot designs and the use of hydrogen gas in the launch tube. Attention also had to be paid to the problem of the obturator drafting behind the model and impacting the model. Of the techniques presented, the obturator cups and hydrogen in the launch tube were successful when properly implemented

  15. Helicity Transformation under the Collision and Merging of Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Dehaas, Timothy

    2016-10-01

    A magnetic flux rope is a tube-like, current carrying plasma embedded in an external magnetic field. The magnetic field lines resemble threads in a rope, which vary in pitch according to radius. Flux ropes are ubiquitous in astrophysical plasmas, and bundles of these structures play an important role in the dynamics of the space environment. They are observed in the solar atmosphere and near-earth environment where they are seen to twist, merge, tear, and writhe. In this MHD context, their global dynamics are bound by rules of magnetic helicity conservation, unless, under a non-ideal process, helicity is transformed through magnetic reconnection, turbulence, or localized instabilities. These processes are tested under experimental conditions in the Large Plasma Device (LAPD). The device is a twenty-meter long, one-meter diameter, cylindrical vacuum vessel designed to generate a highly reproducible, magnetized plasma. Reliable shot-to-shot repetition of plasma parameters and over four hundred diagnostic ports enable the collection of volumetric datasets (measurements of ne, Te, Vp, B, J, E, uflow) as two kink-unstable flux ropes form, move, collide, and merge. Similar experiments on the LAPD have utilized these volumetric datasets, visualizing magnetic reconnection through a topological quasi-separatrix layer, or QSL. This QSL is shown to be spatially coincident with the reconnection rate, ∫ E . dl , and oscillates (although out of phase) with global helicity. Magnetic helicity is observed to have a negative sign and its counterpart, cross helicity, a positive one. These quantities oscillate 8% peak-to-peak, and the changes in helicity are visualized as 1) the transport of helicity (ϕB + E × A) and 2) the dissipation of the helicity - 2 E . B . This work is supported by LANL-UC research Grant and done at the Basic Plasma Science Facility, which is funded by DOE and NSF.

  16. 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.

  17. 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.

  18. Magnetic flux leakage modeling for mechanical damage in transmission pipelines

    SciTech Connect

    Ivanov, P.A.; Zhang, Z.; Yeoh, C.H.; Udpa, L.; Sun, Y.; Udpa, S.S.; Lord, W.

    1998-09-01

    This paper presents a two stage FE model for prediction of magnetic flux leakage, resulting from mechanical damage. In the first stage the stress distribution associated with mechanical damage is obtained from a structural model. In the second stage the stress distribution is incorporated into a magnetic FE model, by mapping stress levels to permeability. MFL signals are calculated and compared with experimental gouge MFL signatures.

  19. Testing of Photomultiplier Tubes in a Magnetic Field

    NASA Astrophysics Data System (ADS)

    Waldron, Zachary; A1 Collaboration

    2016-09-01

    The A1 collaboration at MAMI in Mainz, Germany has designed a neutron detector that can be used in experiments to measure the electric form factor of the neutron. They will measure elastic scattering from the neutron, using the polarized electron beam from MAMI at A1's experimental hall. The detector will be composed of two walls of staggered scintillator bars which will be read out by photomultiplier tubes (PMT), connected to both ends of each scintillator via light guides. The experiment requires a magnetic field with strength of 1 Tesla, 2m away from the first scintillator wall. The resulting fringe field is sufficient to disrupt the PMTs, despite the addition of Mu Metal shielding. The effects of the fringe field on these PMTs was tested to optimize the amplification of the PMTs. A Helmholtz Coil was designed to generate a controlled magnetic field with equivalent strength to the field that the PMTs will encounter. The PMTs were read out using a multi-channel analyzer, were tested at various angles relative to the magnetic field in order to determine the optimal orientation to minimize signal disruption. Tests were also performed to determine: the neutron detector response to cosmic radiation; and the best method for measuring a magnetic field's strength in two dimensions. National Science Foundation Grant No. IIA-1358175.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. Direct measurement of magnetic flux compression on the Z pulsed-power accelerator

    NASA Astrophysics Data System (ADS)

    McBride, R. D.; Bliss, D. E.; Martin, M. R.; Jennings, C. A.; Lamppa, D. C.; Dolan, D. H.; Lemke, R. W.; Rovang, D. C.; Rochau, G. A.; Cuneo, M. E.; Sinars, D. B.; Intrator, T. P.; Weber, T. E.

    2016-10-01

    We report on the progress made to date for directly measuring magnetic flux compression on Z. Each experiment consisted of an initially solid aluminum liner (a cylindrical tube), which was imploded using Z's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-20-T axial seed field, Bz(0), supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by Bz(t) =Bz (0)×[R(0)/R(t)]2, where R is the liner's inner surface radius. With perfect flux conservation, Bz and dBz/dt values exceeding 104 T and 1012 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields directly. We report on our latest efforts to do so using a fiber-optic-based Faraday rotation diagnostic, where the magneto-active portion of the sensor is made from terbium-doped optical fiber. We have now used this diagnostic to measure a flux-compressed magnetic field to over 600 T prior to the imploding liner hitting the on-axis fiber housing. This project was funded in part by Sandia's LDRD program and US DOE-NNSA contract DE-AC04-94AL85000.

  7. 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.

  8. 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.

  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. Electrostatic focal spot correction for x-ray tubes operating in strong magnetic fields

    PubMed Central

    Lillaney, Prasheel; Shin, Mihye; Hinshaw, Waldo; Fahrig, Rebecca

    2014-01-01

    field in addition to the orthogonal field does not affect the electrostatic correction technique. However, rotation of the x-ray tube by 30° toward the MR bore increases the parallel magnetic field magnitude (∼72 mT). The presence of this larger parallel field along with the orthogonal field leads to incomplete correction. Monte Carlo simulations demonstrate that the mean energy of the x-ray spectrum is not noticeably affected by the electrostatic correction, but the output flux is reduced by 7.5%. Conclusions: The maximum orthogonal magnetic field magnitude that can be compensated for using the proposed design is 65 mT. Larger orthogonal field magnitudes cannot be completely compensated for because a pure electrostatic approach is limited by the dielectric strength of the vacuum inside the x-ray tube insert. The electrostatic approach also suffers from limitations when there are strong magnetic fields in both the orthogonal and parallel directions because the electrons prefer to stay aligned with the parallel magnetic field. These challenging field conditions can be addressed by using a hybrid correction approach that utilizes both active shielding coils and biasing electrodes. PMID:25370658

  11. In situ measurements of the plasma bulk velocity near the Io flux tube

    NASA Technical Reports Server (NTRS)

    Barnett, A.

    1985-01-01

    The flow around the Io flux tube was studied by analyzing the eleven spectra taken by the Voyager 1 Plasma Science (PLS) experiment in its vicinity. The bulk plasma parameters were determined using a procedure that uses the full response function of the instrument and the data in all four PLS sensors. The mass density of the plasma in the vicinity of Io is found to be 22,500 + or - 2,500 amu/cu cm and its electron density is found to be 1500 + or - 200/cu cm. The Alfven speed was determined using three independent methods; the values obtained are consistent and taken together yield V sub A = 300 + or - 50 km/sec, corresponding to an Alfven Mach number of 0.19 + or - 0.02. For the flow pattern, good agreement was found with the model of Neubauer (1980), and it was concluded that the plasma flows around the flux tube with a pattern similar to the flow of an incompressible fluid around a long cylinder obstacle of radius 1.26 + or - 0.1 R sub Io.

  12. 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.

  13. MHD-instability of a drop of magnetic fluid in a circular capillary tube

    SciTech Connect

    Tsebers, A.O.

    1987-10-01

    The authors theoretically assess the magnetohydrodynamic kink instability of a droplet of magnetic liquid under film and capillary flow conditions in a tube in the presence of a transverse magnetic field and affected by flexural deformation. The film and tube are considered to be infinitely long. Introducing the surface tensions of the liquid-vapor boundary, the liquid-tube wall boundary, and the vapor-tube wall boundary, the film surface contribution to the total energy of the system is represented, and the threshold value of magnetization necessary for the development of flexural deformation is determined.

  14. Columbia University flow instability experimental program: Volume 7. Single tube tests, critical heat flux test program

    SciTech Connect

    Dougherty, T.; Maciuca, C.; McAssey, E.V. Jr.; Reddy, D.G.; Yang, B.W.

    1992-09-01

    This report deals with critical heat flux (CHF) measurements in vertical down flow of water at low pressures in a round Inconel tube, 96 inches long and 0.62 inch inside diameter. A total of 28 CHF points were obtained. These data were found to correlate linearly with the single variable q, defined as the heat flux required to raise the enthalpy from the inlet value to the saturation value. These results were compared to the published results of Swedish investigators for vertical upflow of water at low pressures in round tubes of similar diameters and various lengths. The parameter q depends on the inlet enthalpy and is a nonlocal variable, thus this correlation is nonlocal unless the coefficients depend upon tube length in a particular prescribed manner. For the low pressure Swedish data, the coefficients are practically independent of length and hence the correlation is nonlocal. In the present investigation only one length was employed, so it is not possible to determine whether the correlation for these data is local or nonlocal, although there is reason to believe that it is local. The same correlation was applied to a large data base (thousands of CHF points) compiled from the published data of a number of groups and found to apply, with reasonable accuracy over a wide range of conditions, yielding sometimes local and sometimes nonlocal correlations. The basic philosophy of data analysis here was not to generate a single correlation which would reproduce all data, but to search for correlations which apply adequately over some range and which might have some mechanistic significance. The tentative conclusion is that at least two mechanisms appear operative, leading to two types of correlations, one local, the other nonlocal.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. Vector magnetogram and dopplergram observation of magnetic flux emergence and its explanation

    NASA Astrophysics Data System (ADS)

    Hongqi, Zhang; Mutao, Song

    1992-03-01

    During 23 28 August 1988, at the Huairou Solar Observation Station of Beijing Observatory, the full development process of the region HR 88059 was observed. It emerged near the center of the solar disk and formed a medium active region. A complete series of vector magnetograms and photospheric and chromospheric Dopplergrams was obtained. From an analysis of these data, combined with some numerical simulations, the following conclusions can be drawn. (1) The emergence of new magnetic flux from enhanced networks followed by sunspot formation is an interesting physical process which can be simply described by MHD numerical simulation. The phenomena accompanying it occur according to a definite law summarized by Zwaan (1985). The condition for gas cooling and sunspot formation seems to be transverse field strength > 50 G together with longitudinal field strength > 700 G. For a period of 4 to 5 hours, the orientation of the transverse field shows little change. The configuration of field lines may be derived from vector magnetograms. The arch filament system can be recognized as an MHD shock. (2) New opposite bipolar features emerge within the former bipolar field with an identical strength which will develop a sunspot group complex. Also, arch filament systems appear there located in the position of flux emergence. The neutral line is often pushed aside and curved, leading to faculae heating and the formation of a current sheet. In spite of complicated Dopplergrams, the same phenomena occur at the site of flux emergence as usual: upward flow appears at the location of the emerging and rapidly varying flux near the magnetic neutral line, and downdraft occurs over large parts of the legs of the emerging flux tubes. The age of magnetic emerging flux (or a sunspot) can be estimated in terms of transverse field strengths: when 50 G < transverse field < 200 G, the longitudinal magnetogram and Dopplergram change rapidly, which indicates a rigourously emerging magnetic flux

  20. Photomultiplier tube calibration based on Na lidar observation and its effect on heat flux bias.

    PubMed

    Liu, Alan Z; Guo, Yafang

    2016-11-20

    Na lidar can measure vertical wind and temperature at high temporal and vertical resolutions, enough to resolve gravity wave perturbations. Heat flux due to dissipating gravity waves is an important quantity that can be derived from such perturbations. When lidar signals are high, a photomultiplier tube (PMT) used to count incoming photons may suffer from the saturation effect, and its output count is not linearly related to incoming photon counts. Corrections to this effect can be measured in a laboratory setting but may have large errors at high count rates. We show that the errors in the PMT correction can cause significant bias in the heat flux calculation due to the inherent correlation between wind and temperature errors. Using the measurements made by Na lidar at the Andes Lidar Observatory with Hamamatsu PMTs, we developed a calibration procedure to remove such PMT correction errors from laboratory measurements. By applying the revised PMT correction curve we demonstrated that the heat flux bias can be removed through this procedure.

  1. 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.

  2. 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

  3. 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).

  4. 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

  5. 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

  6. 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

  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. 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

  9. 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.

  10. 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.

  11. Multiple Scattering of Seismic Waves from Ensembles of Upwardly Lossy Thin Flux Tubes

    NASA Astrophysics Data System (ADS)

    Hanson, Chris S.; Cally, Paul S.

    2015-07-01

    Our previous semi-analytic treatment of - and -mode multiple scattering from ensembles of thin flux tubes (Hanson and Cally, Astrophys. J. 781, 125, 2014a; 791, 129, 2014b) is extended by allowing both sausage and kink waves to freely escape at the top of the model using a radiative boundary condition there. As expected, this additional avenue of escape, supplementing downward loss into the deep solar interior, results in substantially greater absorption of incident - and -modes. However, less intuitively, it also yields mildly to substantially smaller phase shifts in waves emerging from the ensemble. This may have implications for the interpretation of seismic data for solar plage regions, and in particular their small measured phase shifts.

  12. Limited Streamer Tubes for the BaBar Instrumented Flux Return Upgrade

    SciTech Connect

    Lu, C.; /Princeton U.

    2005-10-11

    Starting from the very beginning of their operation the efficiency of the RPC chambers in the BaBar Instrumented Flux Return (IFR) has suffered serious degradation. After intensive investigation, various remediation efforts had been carried out, but without success. As a result the BaBar collaboration decided to replace the dying barrel RPC chambers about two years ago. To study the feasibility of using the Limited Streamer Tube (LST) as the replacement of RPC we carried out an R&D program that has resulted in BaBar's deciding to replace the barrel RPC's with LST's. In this report we summarize the major detector R&D results, and leave other issues of the IFR system upgrade to the future publications.

  13. Confinement and Lattice Quantum-Electrodynamic Electric Flux Tubes Simulated with Ultracold Atoms

    SciTech Connect

    Zohar, Erez; Reznik, Benni

    2011-12-30

    We propose a method for simulating (2+1)D compact lattice quantum-electrodynamics, using ultracold atoms in optical lattices. In our model local Bose-Einstein condensates' (BECs) phases correspond to the electromagnetic vector potential, and the local number operators represent the conjugate electric field. The well-known gauge-invariant Kogut-Susskind Hamiltonian is obtained as an effective low-energy theory. The field is then coupled to external static charges. We show that in the strong coupling limit this gives rise to ''electric flux tubes'' and to confinement. This can be observed by measuring the local density deviations of the BECs, and is expected to hold even, to some extent, outside the perturbative calculable regime.

  14. 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.

  15. Systematic study of Zc+ family from a multiquark color flux-tube model

    NASA Astrophysics Data System (ADS)

    Deng, Chengrong; Ping, Jialun; Huang, Hongxia; Wang, Fan

    2015-08-01

    Inspired by the present experimental results of charged charmonium-like states Zc+, we present a systematic study of the tetraquark states [c u ][c ¯ d ¯ ] in a color flux-tube model with a multibody confinement potential. Our investigation indicates that charged charmonium-like states Zc+(3900 ) or Zc+(3885 ), Zc+(3930 ) , Zc+(4020 ) or Zc+(4025 ), Z1+(4050 ), Z2+(4250 ), and Zc+(4200 ) can be described as a family of tetraquark [c u ][c ¯d ¯] states with the quantum numbers n 2SL+1 J and JP of 1 3S1 and 1+, 2 3S1 and 1+, 1 5S2 and 2+, 1 3P1 and 1-, 1 5D1 and 1+, and 1 3D1 and 1+, respectively. The predicted lowest mass charged tetraquark state [c u ][c ¯ d ¯ ] with 0+ and 1 1S0 lies at 3780 ±10 MeV /c2 in the model. These tetraquark states have compact three-dimensional spatial configurations similar to a rugby ball with higher orbital angular momentum L between the diquark [c u ] and antidiquark [c ¯d ¯] corresponding to a more prolate spatial distribution. The multibody color flux tube, a collective degree of freedom, plays an important role in the formation of those charged tetraquark states. However, the two heavier charged states Zc+(4430 ) and Zc+(4475 ) cannot be explained as tetraquark states [c u ][c ¯d ¯] in this model approach.

  16. Potential micrometeoroid and orbital debris protection system using a gradient magnetic field and magnetic flux compression

    NASA Astrophysics Data System (ADS)

    Giffin, A.; Shneider, M. N.; Miles, R. B.

    2010-08-01

    A system for using a magnetic field in conjunction with conventional shielding configurations to protect against micrometeoroid and orbital debris is presented. Analytical, numerical, and experimental studies of a conductor moving through a gradient magnetic field have been performed. The results show that in the high magnetic Reynolds number regime a conducting object will experience large forces that tend to deform it while moving through the gradient field. Additionally a configuration using magnetic flux compression is introduced to act as a magnetic shock absorber. Separately or together, this technology may augment or replace current protection designs for space systems.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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

  2. On the look-up tables for the critical heat flux in tubes (history and problems)

    SciTech Connect

    Kirillov, P.L.; Smogalev, I.P.

    1995-09-01

    The complication of critical heat flux (CHF) problem for boiling in channels is caused by the large number of variable factors and the variety of two-phase flows. The existence of several hundreds of correlations for the prediction of CHF demonstrates the unsatisfactory state of this problem. The phenomenological CHF models can provide only the qualitative predictions of CHF primarily in annular-dispersed flow. The CHF look-up tables covered the results of numerous experiments received more recognition in the last 15 years. These tables are based on the statistical averaging of CHF values for each range of pressure, mass flux and quality. The CHF values for regions, where no experimental data is available, are obtained by extrapolation. The correction of these tables to account for the diameter effect is a complicated problem. There are ranges of conditions where the simple correlations cannot produce the reliable results. Therefore, diameter effect on CHF needs additional study. The modification of look-up table data for CHF in tubes to predict CHF in rod bundles must include a method which to take into account the nonuniformity of quality in a rod bundle cross section.

  3. 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.

  4. 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.

  5. Induced mass and wave motions in the lower solar atmosphere. I - Effects of shear motion of flux tubes

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Hu, Y. Q.; Nakagawa, Y.; Tandberg-Hanssen, E.

    1983-01-01

    Observations indicate that various dynamic solar phenomena lead to enhanced emission of electromagnetic waves from radio to X-ray wavelengths which can be traced to magnetic activity in the photospheric level. A number of previous investigations have ignored the dynamic responses in the solar atmosphere. On the other hand, Nakagawa et al. (1978, 1981) have studied the atmospheric responses in the frame of MHD in the supersonic super-Alfvenic region. Studies of the slowly varying dynamic response (subsonic) have been unsuccessful because of the requirements of high accuracy in the numerical scheme in which a rigorous mathematical treatment of the boundary conditions is necessary. Recently, a numerical MHD model was constructed by using the full implicit continuous eulerian method. The present investigation makes use of a method which is written in a more convenient numerical code. A two-dimensional, time-dependent, nonplanar MHD model is used to investigate the induced mass and wave motions in the lower solar atmosphere due to the shear motion of flux tubes.

  6. Magnetization plateaux and jumps in frustrated four-leg spin tubes in magnetic fields

    NASA Astrophysics Data System (ADS)

    Rosales, H. D.; Arlego, M.; Gómez Albarracín, F. A.

    2014-12-01

    We study the ground state phase diagram of a frustrated spin-1/2 four-leg tube in an external magnetic field. We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: density matrix renormalization group (DMRG), a low-energy effective Hamiltonian (LEH) and a Hartree variational approach (HVA). We find that in the limit of weakly interacting plaquettes, singlet and triplet states play an important role in the formation of magnetization plateaux. We study the transition regions numerically and analytically, and find that they are described, at first order in a strong- coupling expansion, by an XXZ spin-1/2 chain in a magnetic field. These results are consistent with the DMRG and HVA calculations.

  7. Comparison of conventional and novel quadrupole drift tube magnets inspired by Klaus Halbach

    SciTech Connect

    Feinberg, B.

    1995-02-01

    Quadrupole drift tube magnets for a heavy-ion linac provide a demanding application of magnet technology. A comparison is made of three different solutions to the problem of providing an adjustable high-field-strength quadrupole magnet in a small volume. A conventional tape-wound electromagnet quadrupole magnet (conventional) is compared with an adjustable permanent-magnet/iron quadrupole magnet (hybrid) and a laced permanent-magnet/iron/electromagnet (laced). Data is presented from magnets constructed for the SuperHILAC heavy-ion linear accelerator, and conclusions are drawn for various applications.

  8. The kink instability in infinite cylindrical flux tubes - Eigenvalues for power-law twist profiles

    NASA Astrophysics Data System (ADS)

    Craig, I. J. D.; Robb, T. D.; Sneyd, A. D.; McClymont, A. N.

    1990-04-01

    Simple, accurate methods of calculating ideal MHD instability eigenvalues for infinitely long cylindrical tubes with twist function T(r) are developed. The results show that the most rapidly growing and energetic instabilities occur in the Gold-Hoyle v = 0 field, with the instability progressively weakening with increasing v. However, the maximum force eigenvalue is always small, so that even in the Gold-Hoyle case only a small proportion of the available magnetic energy can be released in the linear phase. The results also confirm that the linear pinch is remarkably weak yet relatively resistant to line-tying. It is shown that the weakness of the force eigenvalue implies that the influence of uniform gas pressure on stability is negligible. Implications for the energy-release mechanism in solar flares are discussed.

  9. Rapidly solidified Ag-Cu eutectics: A comparative study using drop-tube and melt fluxing techniques

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Mullis, A. M.; Cochrane, R. F.

    2016-03-01

    A comparative study of rapid solidification of Ag-Cu eutectic alloy processed via melt fluxing and drop-tube techniques is presented. A computational model is used to estimate the cooling rate and undercooling of the free fall droplets as this cannot be determined directly. SEM micrographs show that both materials consist of lamellar and anomalous eutectic structures. However, below the critical undercooling the morphologies of each are different in respect of the distribution and volume of anomalous eutectic. The anomalous eutectic in flux- undercooled samples preferentially forms at cell boundaries around the lamellar eutectic in the cell body. In drop-tube processed samples it tends to distribute randomly inside the droplets and at much smaller volume fractions. That the formation of the anomalous eutectic can, at least in part, be suppressed in the drop-tube is strongly suggestive that the formation of anomalous eutectic occurs via remelting process, which is suppressed by rapid cooling during solidification.

  10. 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.

  11. The effect of a constraining metal tube on flux pinning induced stress in a long cylindrical superconductor

    NASA Astrophysics Data System (ADS)

    Yang, Xiaobin; Tu, Shan-Tung

    2012-07-01

    The use of an alloy tube to impose pressure on a superconducting cylinder during magnetizing reduces pinning-induced tensile stress in high temperature superconductors has been well established. In this paper the natural contact state between the superconducting cylinder and the metal tube is modeled. An exact solution is obtained for the isotropic magnetoelastic problem with the superconductor behaving magnetically, and an expression for the contact pressure exerted on the superconductor by the metal tube is obtained. This expression explicitly gives the contribution of the ratio of Young's modulus of the superconductor to that of the metal and the ratio of the internal to external radii of the metal tube. The stress profile in the superconductor, subjected to the restriction of metal tube, with both field cooled activation and pulse field activation is analyzed in terms of the Bean critical-state model. The results show that the metal tube can prevent radial expansion of the superconductor and can reduce the maximum tension for field-cooled and pulsed-field activations. These results are important for the selection of materials as well as the optimization of sizes of the alloy tube.

  12. 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.

  13. Supergranular-scale magnetic flux emergence beneath an unstable filament

    NASA Astrophysics Data System (ADS)

    Palacios, J.; Cid, C.; Guerrero, A.; Saiz, E.; Cerrato, Y.

    2015-11-01

    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 Magnetic 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 flux emergence happened very close to a filament barb that was very active in mass motion, as seen in 304 Å images. The observed flux emergence exhibited hectogauss values. The flux 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 magnetic flux 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 magnetic flux 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

  14. System having unmodulated flux locked loop for measuring magnetic fields

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2006-08-15

    A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux 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.

  15. Nonlinear evolution of magnetic flux ropes. I - Low-beta limit

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    We study the nonlinear self-similar evolution of a cylindrical magnetic flux tube with two components of the magnetic field, axial and azimuthal. We restrict ourselves to the case of a plasma of low beta. Introducing a special class of configurations we call 'separable fields', we reduce the problem to an ordinary differential equation. Two cases are to be distinguished: (1) when the total field minimizes on the symmetry axis, the magnetic configuration inexorably collapses, and (2) when, on the other hand, the total field maximizes on the symmetry axis, the magnetic configuration behaves analogously to a nonlinear oscillator. Here we focus on the latter case. The effective potential of the motion contains two terms: a strong repulsive term and a weak restoring term associated with the pinch. We solve the nonlinear differential equation of motion numerically and find that the period of oscillations grows exponentially with the energy of the oscillator. Our treatment emphasizes the role of the force-free configuration as the lowest potential energy state about which the system oscillates.

  16. Decoupling suspension controller based on magnetic flux feedback.

    PubMed

    Zhang, Wenqing; Li, Jie; Zhang, Kun; Cui, Peng

    2013-01-01

    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 magnetic 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 magnetic flux 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.

  17. Energy flux determines magnetic field strength of planets and stars.

    PubMed

    Christensen, Ulrich R; Holzwarth, Volkmar; Reiners, Ansgar

    2009-01-08

    The magnetic 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 flux available for generating the magnetic 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.

  18. Exponentially localized Wannier functions in periodic zero flux magnetic fields

    NASA Astrophysics Data System (ADS)

    De Nittis, G.; Lein, M.

    2011-11-01

    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 flux magnetic 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 magnetic symmetry plays a crucial rôle; to a large class of symmetries for a non-magnetic system, one can associate "magnetic" symmetries of the related magnetic 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 magnetic 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.

  19. INTERPLANETARY MAGNETIC FLUX DEPLETION DURING PROTRACTED SOLAR MINIMA

    SciTech Connect

    Connick, David E.; Smith, Charles W.; Schwadron, Nathan A. E-mail: Charles.Smith@unh.edu

    2011-01-20

    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 magnetic field continues to be depleted at low latitudes throughout the protracted solar minimum reaching levels below previously predicted minima. We obtain a rate of flux removal resulting in magnetic 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 flux 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.

  20. Localized electrons on a lattice with incommensurate magnetic flux

    NASA Astrophysics Data System (ADS)

    Fishman, Shmuel; Shapir, Yonathan; Wang, Xiang-Rong

    1992-11-01

    The magnetic-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 magnetic flux per plaquette (in units of a flux 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.

  1. Counterstreaming electrons in small interplanetary magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Feng, H. Q.; Zhao, G. Q.; Wang, J. M.

    2015-12-01

    Small interplanetary magnetic flux 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 flux ropes contain CSEs, and the percentages of counterstreaming vary from 8% to 98%, with a mean value of 51%. CSEs are often observed in magnetic 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.

  2. Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520

    SciTech Connect

    Cheng, X.; Ding, M. D.; Zhang, J.; Guo, Y.; Sun, X. D.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-10

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s{sup –1}. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  3. Formation of a Double-decker Magnetic Flux Rope in the Sigmoidal Solar Active Region 11520

    NASA Astrophysics Data System (ADS)

    Cheng, X.; Ding, M. D.; Zhang, J.; Sun, X. D.; Guo, Y.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-07-01

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s-1. The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  4. A laboratory study of arched magnetic flux rope eruptions*

    NASA Astrophysics Data System (ADS)

    Tripathi, S.; Gekelman, W. N.

    2010-12-01

    Arched magnetic flux ropes (AMFRs) are arch-shaped twisted magnetic-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 magnetized 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 magnetic field along the curved axis of the AMFR. The vacuum chamber has an additional plasma source and electromagnets to produce the ambient magnetized 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 magnetic flux 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.

  5. Simple explanation of the theory of the total magnetic flux method for the measurement of ferromagnetic cross sections

    SciTech Connect

    Stanley, R.K. )

    1995-01-01

    In a previous paper (Kirkwood and Stanley, 1992), the authors have outlined the total magnetic flux (TMF) method for the inspection of elongated ferromagnetic product, such as tubing, drill pipe, sucker rods, wire rope, and piping in refineries and chemical plants. This paper is presented to provide the scientific background to this nondestructive evaluation (NDE) method, which has not previously been presented, and to provide a list of references in which the technique is known to be used. Because the method detects wall loss in ferromagnetic steel parts, and is often used in conjunction with other NDE methods such as magnetic flux leakage (MFL), it represents yet another technique for rapid volumetric scanning of such parts.

  6. Forecasting F10.7 with Solar Magnetic Flux Transport Modeling (Postprint)

    DTIC Science & Technology

    2012-04-03

    modeling of future magnetic field distributions to predict F10.7 several days ahead. 3 . Global Solar Magnetic Flux Transport [ 8 ] Solar magnetic flux...intervals of the 18 year period investigated. By evolving solar magnetic synoptic maps forward 1–7 days, this new method provides a realistic...that the observed Earth-side solar magnetic field strength and distribution can be used to estimate F10.7 surprisingly well. [ 3 ] Chapman and Boyden

  7. Enhanced magnetic particle transport by integration of a magnetic flux guide: Experimental verification of simulated behavior

    NASA Astrophysics Data System (ADS)

    Wirix-Speetjens, Roel; Fyen, Wim; Boeck, Jo De; Borghs, Gustaaf

    2006-04-01

    In the past, magnetic 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 magnetic particles is firmly established, research groups continue to explore the unique ability of manipulating these particles by applying controlled magnetic forces. One of the challenging tasks in designing magnetic force generating structures remains the generation of large forces for a minimal current consumption. Previously, a simple transporting device for single magnetic particles has been demonstrated using a magnetic 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 magnetic particle moving in the vicinity of a solid wall. Using this model, we now present a technique that enhances the magnetic force up to a factor of 3 using a magnetic flux guide. The larger magnetic force results in an average speed of the particle which increases with a factor of 3. These simulations show good agreement with experimental results.

  8. Lava tube shatter rings and their correlation with lava flux increases at Kīlauea Volcano, Hawai‘i

    USGS Publications Warehouse

    Orr, T.R.

    2011-01-01

    Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava tubes. They are typified by an upraised rim of blocky rubble and a central depression. Prior to this study, shatter rings had not been observed forming, and, thus, were interpreted in many ways. This paper describes the process of formation for shatter rings observed at Kīlauea Volcano during November 2005–July 2006. During this period, tilt data, time-lapse images, and field observations showed that episodic tilt changes at the nearby Pu‘u ‘Ō‘ō cone, the shallow magmatic source reservoir, were directly related to fluctuations in the level of lava in the active lava tube, with periods of deflation at Pu‘u ‘Ō‘ō correlating with increases in the level of the lava stream surface. Increases in lava level are interpreted as increases in lava flux, and were coincident with lava breakouts from shatter rings constructed over the lava tube. The repetitive behavior of the lava flux changes, inferred from the nearly continuous tilt oscillations, suggests that shatter rings form from the repeated rise and fall of a portion of a lava tube roof. The locations of shatter rings along the active lava tube suggest that they form where there is an abrupt decrease in flow velocity through the tube, e.g., large increase in tube width, abrupt decrease in tube slope, and (or) sudden change in tube direction. To conserve volume, this necessitates an abrupt increase in lava stream depth and causes over-pressurization of the tube. More than a hundred shatter rings have been identified on volcanoes on Hawai‘i and Maui, and dozens have been reported from basaltic lava fields in Iceland, Australia, Italy, Samoa, and the mainland United States. A quick study of other basaltic lava fields worldwide, using freely available satellite imagery, suggests that they might be even more common than previously thought. If so, this confirms that episodic

  9. Zero-energy traps and magnetic flux read-out in graphene

    NASA Astrophysics Data System (ADS)

    Downing, Charles A.; Gupta, Kumar S.; Portnoi, Mikhail E.

    2014-03-01

    There is a widespread belief that electrostatic confinement of graphene charge carriers, which resemble massless Dirac fermions, is impossible as a result of the Klein paradox. We show that full confinement is indeed possible for zero-energy states in pristine graphene with careful modulation of the strength of the trapping electrostatic potential. The addition of a magnetic flux tube to the system requires one to perform a one-parameter self-adjoint extension of the Dirac Hamiltonian to completely define the spectrum of the zero-modes, which can be carried out using the method of deficiency indices developed by von Neumann. We propose such a magnetic vector potential as an additional means to control these optimal quantum dots supporting zero-energy states and bring about confinement-deconfinement on demand. The considered system can be utilised in novel graphene-based magnetic read-out devices. C. A. Downing, D. A. Stone, and M. E. Portnoi, Phys. Rev. B 84, 155437 (2011). C. A. Downing, K. S. Gupta, and M. E. Portnoi (in preparation).

  10. Magnetization plateaus and jumps in a frustrated four-leg spin tube under a magnetic field

    NASA Astrophysics Data System (ADS)

    Gómez Albarracín, F. A.; Arlego, M.; Rosales, H. D.

    2014-11-01

    We study the ground state phase diagram of a frustrated spin-1/2 four-leg spin tube in an external magnetic field. We explore the parameter space of this model in the regime of all-antiferromagnetic exchange couplings by means of three different approaches: analysis of low-energy effective Hamiltonian, a Hartree variational approach, and density matrix renormalization group for finite clusters. We find that in the limit of weakly interacting plaquettes, low-energy singlet, triplet, and quintuplet states play an important role in the formation of fractional magnetization plateaus. We study the transition regions numerically and analytically, and find that they are described, at first order in a strong-coupling expansion, by an X X Z spin-1/2 chain in a magnetic field; the second-order terms give corrections to the X X Z model. All techniques provide consistent results which allow us to predict the existence of fractional plateaus in an important region in the space of parameters of the model.

  11. Experimental study on heat transfer enhancement of laminar ferrofluid flow in horizontal tube partially filled porous media under fixed parallel magnet bars

    NASA Astrophysics Data System (ADS)

    Sheikhnejad, Yahya; Hosseini, Reza; Saffar Avval, Majid

    2017-02-01

    In this study, steady state laminar ferroconvection through circular horizontal tube partially filled with porous media under constant heat flux is experimentally investigated. Transverse magnetic fields were applied on ferrofluid flow by two fixed parallel magnet bar positioned on a certain distance from beginning of the test section. The results show promising notable enhancement in heat transfer as a consequence of partially filled porous media and magnetic field, up to 2.2 and 1.4 fold enhancement were observed in heat transfer coefficient respectively. It was found that presence of both porous media and magnetic field simultaneously can highly improve heat transfer up to 2.4 fold. Porous media of course plays a major role in this configuration. Virtually, application of Magnetic field and porous media also insert higher pressure loss along the pipe which again porous media contribution is higher that magnetic field.

  12. Estimates of magnetic flux, and energy balance in the plasma sheet during substorm expansion

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Birn, Joachim; Pulkkinen, Tuija

    1996-01-01

    The energy and magnetic flux budgets of the magnetotail plasma sheet during substorm expansion are investigated. The possible mechanisms that change the energy content of the closed field line region which contains all the major dissipation mechanisms of relevance during substorms, are considered. The compression of the plasma sheet mechanism and the diffusion mechanism are considered and excluded. It is concluded that the magnetic reconnection mechanism can accomplish the required transport. Data-based empirical magnetic field models are used to investigate the magnetic flux transport required to account for the observed magnetic field dipolarizations in the inner magnetosphere. It is found that the magnetic flux permeating the current sheet is typically insufficient to supply the required magnetic flux. It is concluded that no major substorm-type magnetospheric reconfiguration is possible in the absence of magnetic reconnection.

  13. Evidence for globally coherent variability in solar magnetic flux emergence

    NASA Technical Reports Server (NTRS)

    Golub, L.; Vaiana, G. S.

    1980-01-01

    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 magnetic flux emergence. Major variations in the rate of flux 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.

  14. Properties of longitudinal flux tube waves. II. Limiting shock strength behavior

    NASA Astrophysics Data System (ADS)

    Cuntz, M.

    2004-06-01

    We extend our previous work on analytic evaluations of properties of longitudinal tube waves to waves propagating in gravitational atmospheres. We derive an expression for the limiting shock strength and discuss the behavior of the shock strength in tubes of different geometry. It is found that a height-independent value for the limiting strength is attained for constant cross-section tubes and exponential tubes, whereas for wine-glass tubes the limiting shock strength increases with height due to the increase of the tube cross section. The limiting shock strength is well reproduced by time-dependent simulations. The derived limiting shock strength as well as the energy dissipation rate of the waves show significant similarities to acoustic waves. The limiting shock strength allows to estimate the heating potential of waves in the absence of detailed time-dependent computations.

  15. ENERGY INJECTION VIA FLUX EMERGENCE ON THE SUN DEPENDING ON THE GEOMETRIC SHAPE OF MAGNETIC FIELD

    SciTech Connect

    Magara, T.

    2011-04-20

    Flux emergence is a complicated process involving flow and magnetic field, which provides a way of injecting magnetic 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 magnetic field vectors. By using this quantity, we demonstrate that the geometric shape of magnetic field might play an important role in the energy injection via flux emergence.

  16. Testing a solar coronal magnetic field extrapolation code with the Titov-Démoulin magnetic flux rope model

    NASA Astrophysics Data System (ADS)

    Jiang, Chao-Wei; Feng, Xue-Shang

    2016-01-01

    In the solar corona, the magnetic flux rope is believed to be a fundamental structure that accounts for magnetic free energy storage and solar eruptions. Up to the present, the extrapolation of the magnetic field from boundary data has been the primary way to obtain fully three-dimensional magnetic information about the corona. As a result, the ability to reliably recover the coronal magnetic flux rope is important for coronal field extrapolation. In this paper, our coronal field extrapolation code is examined with an analytical magnetic flux rope model proposed by Titov & Démoulin, which consists of a bipolar magnetic configuration holding a semi-circular line-tied flux 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 magnetic topological interfaces formed between the flux rope and the surrounding arcade, i.e., the “hyperbolic flux 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 magnetic flux rope in the solar corona as long as the vector magnetogram satisfies the force-free constraints.

  17. Critical heat-flux characteristics of R-113 boiling two-phase flow in twisted-tape-inserted tubes

    SciTech Connect

    Lee, Sangryoul; Inoue, Akira; Takahashi, Minoru

    1996-07-01

    This paper presents experimental data on the critical heat flux (CHF) in twisted-tape-inserted tubes over a wide quality range of {minus}0.25 to 0.8. The influences of quality, twist ratio, mass velocity, and clearance between the twisted tape and tube inner wall on CHF were investigated. In the subcooled region, it was observed, using an infrared thermoviewer, that CHF was initiated locally at the wall near the twisted tape. Consequently, twisted tape insertion with small tape-well clearance decreased CHF to below the value of the empty tubes at a low flow rate. This decrease was found to be avoidable by adjusting the clearance. In the net quality region, CHF of the twisted-tape-inserted tubes increased with increasing flow rate contrary to the case of the empty tubes. However, CHF in the net quality region was also decreased by insertion of twisted tapes with high twist ratio (loosely twisted tapes) at a very low flow rate.

  18. Eddy-current inspection of ferromagnetic tubing using pulsed magnetic saturation

    SciTech Connect

    Dodd, C V; Deeds, W E

    1986-07-01

    A pulsed eddy-current system has been designed and developed for nondestructive evaluation of 2.25Cr-1Mo steam generator tubing from the bore side. Since the tubing is ferromagnetic, a large current pulse is sent through a driver coil to produce magnetic saturation all the way through the tube wall. A pickup coil produces an output pulse that is dependent upon the tube properties as well as the driving pulse. The output pulse heights at selected times are used as data that are computer-correlated with calibration data taken from machined standards. Performance data, circuit diagrams, and computer programs are given for the system, which has been demonstrated to detect small flaws located near the outside of a thick ferromagnetic tube.

  19. Experiments on plasma immersion ion implantation inside conducting tubes embedded in an external magnetic field

    NASA Astrophysics Data System (ADS)

    Pillaca, E. J. D. M.; Ueda, M.; Reuther, H.; Pichon, L.; Lepienski, C. M.

    2015-12-01

    Tubes of stainless steel (SS) embedded in external magnetic field were used to study the effects of plasma immersion ion implantation (PIII) as a function of their diameter. The study was complemented with and without a grounded auxiliary electrode (AE) placed at the axis of the tube. During the discharge tests in tubes of larger diameter (D = 11 cm), with and without AE, nitrogen gas breakdown was established inside the tube at pressures near 2.0 × 10-2 mbar. Under the same operation conditions, stable plasmas with similar PIII current densities were obtained for both arrangements. Reducing the diameter of the tube (D = 1.5 cm) turned the plasma unstable and made it inappropriate for ion implantation. This situation was solved by supplying gas at higher pressure or using higher magnetic field, without the presence of an AE. Under these conditions, nitrogen PIII treatments of these small diameter tubes were performed but gave not the best implantation results yet. Our results have also shown higher ion implantation current density (16 mA/cm2) in tube of intermediate diameter (D = 4 cm) using AE, compared to largest diameter tube used. In this case, a thick nitrogen layer of about 9 μm was obtained in the SS sample placed inside the tube. As a consequence of this, its structural and mechanical properties were enhanced. These results are attributed to the thermal diffusion promoted by ions hitting the inner wall in a large number due to the presence of the AE and the magnetic field.

  20. Magnetic reconnection in 3D magnetosphere models: magnetic separators and open flux production

    NASA Astrophysics Data System (ADS)

    Glocer, A.; Dorelli, J.; Toth, G.; Komar, C. M.; Cassak, P.

    2014-12-01

    There are multiple competing definitions of magnetic 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 magnetic 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 magnetic nulls. A separator in the magnetosphere represents the intersection of four distinct magnetic 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 flux production, and is one measure of the reconnection rate. We present three methods for locating magnetic 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 Flux Transfer Events (FTEs) and Kelvin-Helmholtz instability.

  1. 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.

  2. Investigation of electron trajectories of an x-ray tube in magnetic fields of MR scanners.

    PubMed

    Wen, Zhifei; Fahrig, Rebecca; Conolly, Steven; Pelc, Norbert J

    2007-06-01

    A hybrid x-ray/MR system combining an x-ray fluoroscopic system and an open-bore magnetic resonance (MR) system offers advantages from both powerful imaging modalities and thus can benefit numerous image-guided interventional procedures. In our hybrid system configurations, the x-ray tube and detector are placed in the MR magnet and therefore experience a strong magnetic field. The electron beam inside the x-ray tube can be deflected by a misaligned magnetic field, which may damage the tube. Understanding the deflection process is crucial to predicting the electron beam deflection and avoiding potential damage to the x-ray tube. For this purpose, the motion of an electron in combined electric (E) and magnetic (B) fields was analyzed theoretically to provide general solutions that can be applied to different geometries. For two specific cases, a slightly misaligned strong field and a perpendicular weak field, computer simulations were performed with a finite-element method program. In addition, experiments were conducted using an open MRI magnet and an inserted electromagnet to quantitatively verify the relationship between the deflections and the field misalignment. In a strong (B > E/c; c: speed of light) and slightly misaligned magnetic field, the deflection in the plane of E and B caused by electrons following the magnetic field lines is the dominant component compared to the deflection in the E X B direction due to the drift of electrons. In a weak magnetic field (B < or = E/c), the main deflection is in the E x B direction and is caused by the perpendicular component of the magnetic field.

  3. Recent experience in the fabrication and brazing of ceramic beam tubes for kicker magnets at FNAL

    SciTech Connect

    Ader, C.R.; Jensen, C.; Reilly, R.; Snee, D.; Wilson, J.H.; /Fermilab

    2008-06-01

    Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermi National Accelerator Laboratory. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil (titanium/incusil) alloy brazing material are stacked in the furnace and then brazed in the furnace at 1000 C. The ceramic specified is 99.8% Alumina, Al{sub 2}O{sub 3}, a strong recrystallized high-alumina fabricated by slip casting. Recent experience at Fermilab with the fabrication and brazing of these tubes has brought to light numerous problems including tube breakage and cracking and also the difficulty of brazing the tube to produce a leak-tight joint. These problems may be due to the ceramic quality, voids in the ceramic, thinness of the wall, and micro-cracks in the ends which make it difficult to braze because it cannot fill tiny surface cracks which are caused by grain pullout during the cutting process. Solutions which are being investigated include lapping the ends of the tubes before brazing to eliminate the micro-cracks and also metallization of the tubes.

  4. Beta electron fluxes inside a magnetic plasma cavern: Calculation and comparison with experiment

    NASA Astrophysics Data System (ADS)

    Stupitskii, E. L.; Smirnov, E. V.; Kulikova, N. A.

    2010-12-01

    We study the possibility of electrostatic blanking of beta electrons in the expanding spherical blob of a radioactive plasma in a rarefied ionosphere. From numerical studies on the dynamics of beta electrons departing a cavern, we obtain the form of a function that determines the portion of departing electrons and calculate the flux density of beta electrons inside the cavern in relation to the Starfish Prime nuclear blast. We show that the flux density of electrons in geomagnetic flux tubes and inside the cavern depend on a correct allowance for the quantity of beta electrons returning to the cavern. On the basis of a physical analysis, we determine the approximate criterion for the return of electrons from a geomagnetic flux tube to the cavern. We compare calculation results in terms of the flux density of beta electrons inside the cavern with the recently published experimental results from operation Starfish Prime.

  5. Modeling longitudinal motions of thermal O+ and H+ ions in magnetic field tube convective through daytime polar cusp

    NASA Astrophysics Data System (ADS)

    Zinin, L. V.

    1985-03-01

    The altitude profile of the concentrations and velocities of thermal ions in a magnetic field tube passing convectively through the day-time polar cusp to the cap undergoes a considerable dynamic restructuring. With the intersection of the cusp for a few minutes, the plasma experiences a short term heating and additional ionization by low energy electrons close to and below the F-layer maximum, after which the field tube relaxes. A modified nonsteady-state polar wind model is used to analyze the longitudinal motions of ions in a field tube about 50,000 km long, both for O(+) and H(+) ions, and to estimate the flow of these ions into the magnetosphere. The results of calculating the fluxes F(O+) and F(H+) as well as the longitudinal velocities V(O+) and V(H+) are summarized in two tables for times of from 0 to 160 minutes after exiting the cusp for altitudes of 600, 1,000, 1,500, 2,050, 4,000, 7,920 and 23,050 km. A hydrodynamic mechanism for the entry of thermal O(+) ions from the polar ionosphere into magnetosphere is described; it must play a considerable part in the observed filling of the magnetosphere with energetic O(+) ions.

  6. Length and time for development of laminar flow in tubes following a step increase of volume flux

    NASA Astrophysics Data System (ADS)

    Chaudhury, Rafeed A.; Herrmann, Marcus; Frakes, David H.; Adrian, Ronald J.

    2015-01-01

    Laminar flows starting up from rest in round tubes are relevant to numerous industrial and biomedical applications. The two most common types are flows driven by an abruptly imposed constant pressure gradient or by an abruptly imposed constant volume flux. Analytical solutions are available for transient, fully developed flows, wherein streamwise development over the entrance length is absent (Szymanski in J de Mathématiques Pures et Appliquées 11:67-107, 1932; Andersson and Tiseth in Chem Eng Commun 112(1):121-133, 1992, respectively). They represent the transient responses of flows in tubes that are very long compared with the entrance length, a condition that is seldom satisfied in biomedical tube networks. This study establishes the entrance (development) length and development time of starting laminar flow in a round tube of finite length driven by a piston pump that produces a step change from zero flow to a constant volume flux for Reynolds numbers between 500 and 3,000. The flows are examined experimentally, using stereographic particle image velocimetry and computationally using computational fluid dynamics, and are then compared with the known analytical solutions for fully developed flow conditions in infinitely long tubes. Results show that step function volume flux start-up flows reach steady state and fully developed flow five times more quickly than those driven by a step function pressure gradient, a 500 % change when compared with existing estimates. Based on these results, we present new, simple guidelines for achieving experimental flows that are fully developed in space and time in realistic (finite) tube geometries. To a first approximation, the time to achieve steady spatially developing flow is nearly equal to the time needed to achieve steady, fully developed flow. Conversely, the entrance length needed to achieve fully developed transient flow is approximately equal to the length needed to achieve fully developed steady flow. Beyond this

  7. Enhancement of thermoelectric properties in benzene molecule junction by the magnetic flux

    NASA Astrophysics Data System (ADS)

    Li, Haidong; Wang, Yuan; kang, Xiubao; Liu, Shaohui; Li, Ruixue

    2017-02-01

    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 magnetic flux. The reason for such a behavior is that the quantum interference caused by the magnetic 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 magnetic flux and the magnitude of Z T may exceed 2 under some specific magnetic flux and onsite Coulomb interaction.

  8. Prediction method of flux loss in anisotropic NdFeB/SmFeN hybrid magnets

    NASA Astrophysics Data System (ADS)

    Fukunaga, Hirotoshi; Murata, Hiroki; Yanai, Takeshi; Nakano, Masaki; Yamashita, Fumitoshi

    2010-05-01

    We systematically evaluated the initial flux loss of anisotropic HDDR-NdFeB/RD-SmFeN hybrid bonded magnets. The measured flux loss values were compared with those obtained by two prediction methods based on our previous proposal. Consequently, it was clarified that the initial flux loss of anisotropic bonded magnets can be predicted from demagnetization curves at room and exposure temperatures of the corresponding hybrid magnets, which suggests that the method proposed previously for isotropic magnets can be also applicable to anisotropic ones.

  9. Structure of a magnetic flux annihilation layer formed by the collision of supersonic, magnetized plasma flows

    SciTech Connect

    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.

    2016-05-31

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and magnetized aluminum plasma flows. The anti parallel magnetic 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 the in-flowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.

  10. Structure of a magnetic flux annihilation layer formed by the collision of supersonic, magnetized plasma flows

    DOE PAGES

    Suttle, L. G.; Hare, J. D.; Lebedev, S. V.; ...

    2016-05-31

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counter-streaming, supersonic and magnetized aluminum plasma flows. The anti parallel magnetic 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 magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.« less

  11. Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows.

    PubMed

    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

    2016-06-03

    We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic 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 magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.

  12. Experimental Investigation of the Stability of a Single and Multiple Magnetic Flux Ropes

    NASA Astrophysics Data System (ADS)

    Furno, I.; Intrator, T.; Hemsing, E.

    2003-12-01

    Both the stability of a single magnetic flux rope and the interaction between multiple magnetic flux ropes are fundamental issues in the dynamics of the solar corona. Examples are in coronal mass ejections, in which highly twisted flux ropes are believed to play a crucial role, and in solar flares and large-scale eruptions in which transport of twist through magnetic reconnection is observed between distinct coronal flux systems. To study the interaction of magnetic flux 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 magnetic reconnection during the coalescence of parallel current channels. Commercial plasma guns are used to inject magnetic helicity into hydrogen plasma column (r = 2 cm radius, L = 0.2-3 m length). Multiple flux 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 magnetic field parallel to the current channels. The azimuthal (Bθ = 0-100 Gauss) and axial (Bz = 0-1000 Gauss) magnetic field components as well as the plasma density (1012}-10{14 cm-3) can be varied independently. In particular, the twist of magnetic 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 flux rope and the interaction of two flux ropes are studied in the RSX operational space. Magnetic data and visible light emission from a fast CCD camera are presented showing twisting and braiding of magnetic flux ropes.

  13. BUILDUP OF MAGNETIC SHEAR AND FREE ENERGY DURING FLUX EMERGENCE AND CANCELLATION

    SciTech Connect

    Fang Fang; Manchester, Ward IV; Van der Holst, Bart; Abbett, William P.

    2012-07-20

    We examine a simulation of flux emergence and cancellation, which shows a complex sequence of processes that accumulate free magnetic 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 magnetic polarities, builds up the magnetic shear. Tether-cutting reconnection above the PIL then produces longer sheared magnetic field lines that extend higher into the corona, where a sigmoidal structure forms. Most significantly, reconnection and upward-energy-flux transfer are found to occur even as magnetic flux 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 magnetic flux and formation of sunspots.

  14. Energy Loss of Solar p Modes due to the Excitation of Magnetic Sausage Tube Waves: Importance of Coupling the Upper Atmosphere

    NASA Astrophysics Data System (ADS)

    Gascoyne, A.; Jain, R.; Hindman, B. W.

    2014-07-01

    We consider damping and absorption of solar p modes due to their energy loss to magnetic tube waves that can freely carry energy out of the acoustic cavity. The coupling of p modes and sausage tube waves is studied in a model atmosphere composed of a polytropic interior above which lies an isothermal upper atmosphere. The sausage tube waves, excited by p modes, propagate along a magnetic fibril which is assumed to be a vertically aligned, stratified, thin magnetic flux tube. The deficit of p-mode energy is quantified through the damping rate, Γ, and absorption coefficient, α. The variation of Γ and α as a function of frequency and the tube's plasma properties is studied in detail. Previous similar studies have considered only a subphotospheric layer, modeled as a polytrope that has been truncated at the photosphere. Such studies have found that the resulting energy loss by the p modes is very sensitive to the upper boundary condition, which, due to the lack of an upper atmosphere, have been imposed in a somewhat ad hoc manner. The model presented here avoids such problems by using an isothermal layer to model the overlying atmosphere (chromosphere, and, consequently, allows us to analyze the propagation of p-mode-driven sausage waves above the photosphere. In this paper, we restrict our attention to frequencies below the acoustic cut off frequency. We demonstrate the importance of coupling all waves (acoustic, magnetic) in the subsurface solar atmosphere with the overlying atmosphere in order to accurately model the interaction of solar f and p modes with sausage tube waves. In calculating the absorption and damping of p modes, we find that for low frequencies, below ≈3.5 mHz, the isothermal atmosphere, for the two-region model, behaves like a stress-free boundary condition applied at the interface (z = -z 0).

  15. Nano-cavities observed in a 316SS PWR Flux Thimble Tube Irradiated to 33 and 70 dpa

    SciTech Connect

    Edwards, Danny J.; Garner, Francis A.; Bruemmer, Stephen M.; Efsing, Pal G.

    2009-02-28

    The radiation-induced microstructure of a cold-worked 316SS flux thimble tube from an operating pressurized water reactor (PWR) was examined. Two irradiated conditions, 33 dpa at 290ºC and 70 dpa at 315ºC were examined by transmission electron microscopy. The original dislocation network had completely disappeared and was replaced by fine dispersions of Frank loops and small nano-cavities at high densities. The latter appear to be bubbles containing high levels of helium and hydrogen. An enhanced distribution of these nano-cavities was found at grain boundaries and may play a role in the increased susceptibility of the irradiated 316SS to intergranular failure of specimens from this tube during post-irradiation slow strain rate testing in PWR water conditions.

  16. Magnetic Flux Concentrations in Stratified Turbulent Plasma Due to Negative Effective Magnetic Pressure Instability

    NASA Astrophysics Data System (ADS)

    Jabbari, S.; Brandenburg, A.

    2014-12-01

    al. 2013). When the field is vertical, the resulting magnetic flux concentrations lead to the magnetic 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 magnetic spots (Brandenburg et al. 2014).

  17. Magnetic flux superperiods in fractional quantum Hall interferometers

    NASA Astrophysics Data System (ADS)

    Camino, F. E.; Lin, P. V.; Goldman, V. J.

    2010-03-01

    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 magnetic field periods in the different size devices and review the evidence that the flux 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).

  18. 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.

  19. Measurement of conductivity and permittivity on samples sealed in nuclear magnetic resonance tubes

    SciTech Connect

    Huang, W.; Angell, C. A.; Yarger, J. L.; Richert, R.

    2013-07-15

    We present a broadband impedance spectroscopy instrument designed to measure conductivity and/or permittivity for samples that are sealed in glass tubes, such as the standard 5 mm tubes used for nuclear magnetic resonance experiments. The calibrations and corrections required to extract the dielectric properties of the sample itself are outlined. It is demonstrated that good estimates of the value of dc-conductivity can be obtained even without correcting for the effects of glass or air on the overall impedance. The approach is validated by comparing data obtained from samples sealed in nuclear magnetic resonance tubes with those from standard dielectric cells, using glycerol and butylmethylimidazolium-hexafluorophosphate as respective examples of a molecular and an ionic liquid. This instrument and approach may prove useful for other studies of permittivity and conductivity where contact to the metal electrodes or to the ambient atmosphere needs to be avoided.

  20. Angular magnetic field beam improves efficiency in klystrons and traveling wave tubes

    NASA Technical Reports Server (NTRS)

    Neugebauer, W.

    1973-01-01

    Special lens shaping allows variation of focusing strength with radius. Lens can be either converging or diverging depending on charge of particles and direction of angular magnetic field. There is potential use for lens in particle analyzers, electron beam welding systems, microwave tube refocusing systems, and possible display type devices.

  1. The magnetic, basal, and radiative-equilibrium components in Mount Wilson Ca II H + K fluxes

    SciTech Connect

    Schrijver, C.J.; Dobson, A.K.; Radick, R.R.; Joint Institute for Laboratory Astrophysics, Boulder, CO )

    1989-06-01

    Mount Wilson Ca II H + K flux measurements of cool dwarf stars are analyzed and compared with stellar Mg II h + k fluxes, variability amplitudes, rotation rates, and solar data. It is concluded that the Mount Wilson Ca II H + K fluxes comprise three principal parts: (1) a photospheric contribution in the line wings, (2) a basal chromospheric component that appears to be unrelated to stellar magnetic activity and is, therefore, possibly nonmagnetic in origin, and (3) a chromospheric component which is associated with magnetically active regions and the (quiet and active) network. The basal chromosphere appears to cover the entire surface of magnetically inactive stars. The basal Ca II H + K flux density for solar-type stars equals the average emission observed in the centers of solar supergranulation cells, where the magnetic flux density is small. 27 refs.

  2. The magnetic, basal, and radiative-equilibrium components in Mount Wilson Ca II H + K fluxes

    NASA Technical Reports Server (NTRS)

    Schrijver, C. J.; Dobson, Andrea K.; Radick, Richard R.

    1989-01-01

    Mount Wilson Ca II H + K flux measurements of cool dwarf stars are analyzed and compared with stellar Mg II h + k fluxes, variability amplitudes, rotation rates, and solar data. It is concluded that the Mount Wilson Ca II H + K fluxes comprise three principal parts: (1) a photospheric contribution in the line wings, (2) a basal chromospheric component that appears to be unrelated to stellar magnetic activity and is, therefore, possibly nonmagnetic in origin, and (3) a chromospheric component which is associated with magnetically active regions and the (quiet and active) network. The basal chromosphere appears to cover the entire surface of magnetically inactive stars. The basal Ca II H + K flux density for solar-type stars equals the average emission observed in the centers of solar supergranulation cells, where the magnetic flux density is small.

  3. Implementing and diagnosing magnetic flux compression on the Z pulsed power accelerator

    SciTech Connect

    McBride, Ryan D.; Bliss, David E.; Gomez, Matthew R.; Hansen, Stephanie B.; Martin, Matthew R.; Jennings, Christopher Ashley; Slutz, Stephen A.; Rovang, Dean C.; Knapp, Patrick F.; Schmit, Paul F.; Awe, Thomas James; Hess, M. H.; Lemke, Raymond W.; Dolan, D. H.; Lamppa, Derek C.; Jobe, Marc Ronald Lee; Fang, Lu; Hahn, Kelly D.; Chandler, Gordon A.; Cooper, Gary Wayne; Ruiz, Carlos L.; Maurer, A. J.; Robertson, Grafton Kincannon; Cuneo, Michael E.; Sinars, Daniel; Tomlinson, Kurt; Smith, Gary; Paguio, Reny; Intrator, Tom; Weber, Thomas; Greenly, John

    2015-11-01

    We report on the progress made to date for a Laboratory Directed Research and Development (LDRD) project aimed at diagnosing magnetic flux compression on the Z pulsed-power accelerator (0-20 MA in 100 ns). Each experiment consisted of an initially solid Be or Al liner (cylindrical tube), which was imploded using the Z accelerator's drive current (0-20 MA in 100 ns). The imploding liner compresses a 10-T axial seed field, B z ( 0 ) , supplied by an independently driven Helmholtz coil pair. Assuming perfect flux conservation, the axial field amplification should be well described by B z ( t ) = B z ( 0 ) x [ R ( 0 ) / R ( t )] 2 , where R is the liner's inner surface radius. With perfect flux conservation, B z ( t ) and dB z / dt values exceeding 10 4 T and 10 12 T/s, respectively, are expected. These large values, the diminishing liner volume, and the harsh environment on Z, make it particularly challenging to measure these fields. We report on our latest efforts to do so using three primary techniques: (1) micro B-dot probes to measure the fringe fields associated with flux compression, (2) streaked visible Zeeman absorption spectroscopy, and (3) fiber-based Faraday rotation. We also mention two new techniques that make use of the neutron diagnostics suite on Z. These techniques were not developed under this LDRD, but they could influence how we prioritize our efforts to diagnose magnetic flux compression on Z in the future. The first technique is based on the yield ratio of secondary DT to primary DD reactions. The second technique makes use of the secondary DT neutron time-of-flight energy spectra. Both of these techniques have been used successfully to infer the degree of magnetization at stagnation in fully integrated Magnetized Liner Inertial Fusion (MagLIF) experiments on Z [P. F. Schmit et al. , Phys. Rev. Lett. 113 , 155004 (2014); P. F. Knapp et al. , Phys. Plasmas, 22 , 056312 (2015)]. Finally, we present some recent developments for designing

  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. Design and characterization of a device to quantify the magnetic drug targeting efficiency of magnetic nanoparticles in a tube flow phantom by magnetic particle spectroscopy

    NASA Astrophysics Data System (ADS)

    Radon, Patricia; Löwa, Norbert; Gutkelch, Dirk; Wiekhorst, Frank

    2017-04-01

    The aim of magnetic drug targeting (MDT) is to transfer a therapeutic drug coupled to magnetic nanoparticles (MNP) to desired disease locations (e.g. tumor region) with the help of magnetic field gradients. To transfer the MDT approach into clinical practice a number of important issues remain to be solved. We developed and characterized an in-vitro flow phantom to provide a defined and reproducible MDT environment. The tube system of the flow phantom is directed through the detection coil of a magnetic particle spectroscopy (MPS) device to determine the targeting efficiency. MPS offers an excellent temporal resolution of seconds and an outstanding specific sensitivity of some nanograms of iron. In the flow phantom different MNP types, magnet geometries and tube materials can be employed to vary physical parameters like diameter, flow rate, magnetic targeting gradient, and MNP properties.

  6. MMS observations of small magnetic flux ropes in the near-tail (X > -11 Re)

    NASA Astrophysics Data System (ADS)

    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.

    2015-12-01

    Magnetic reconnection is the most important energy conversion process in the Earth's magnetotail. Flux ropes are helical magnetic 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 flux 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 magnetic and electric fields measurements are near ideal for the investigation of secondary island - type flux ropes carried Earthward from downstream reconnnection sites, as well as their interaction with the strong dipolar magnetic fields of the inner magnetosphere. We present and analyze initial MMS magnetic field measurements of small flux ropes in the near-tail during the commissioning phase while the spacecraft were in a "string-­of-­pearls" configuration.

  7. Superconducting Quantum Interference Devices for the Detection of Magnetic Flux and Application to Airborne High Frequency Direction Finding

    DTIC Science & Technology

    2015-03-26

    SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES FOR THE DETECTION OF MAGNETIC FLUX AND APPLICATION TO AIRBORNE HIGH FREQUENCY DIRECTION FINDING THESIS...SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES FOR THE DETECTION OF MAGNETIC FLUX AND APPLICATION TO AIRBORNE HIGH FREQUENCY DIRECTION FINDING THESIS Presented to the...SUPERCONDUCTING QUANTUM INTERFERENCE DEVICES FOR THE DETECTION OF MAGNETIC FLUX AND APPLICATION TO AIRBORNE HIGH FREQUENCY DIRECTION FINDING THESIS Travis

  8. In-tube magnetic solid phase microextraction of some fluoroquinolones based on the use of sodium dodecyl sulfate coated Fe3O4 nanoparticles packed tube.

    PubMed

    Manbohi, Ahmad; Ahmadi, Seyyed Hamid

    2015-07-23

    In-tube magnetic solid phase microextraction (in-tube MSPME) of fluoroquinolones from water and urine samples based on the use of sodium dodecyl sulfate (SDS) coated Fe3O4 nanoparticles packed tube has been reported. After the preparation of Fe3O4 nanoparticles (NPs) by a batch synthesis, these NPs were introduced into a stainless steel tube by a syringe and then a strong magnet was placed around the tube, so that the Fe3O4 NPs were remained in the tube and the tube was used in the in-tube SPME-HPLC/UV for the analysis of fluoroquinolones in water and urine samples. Plackett-Burman design was employed for screening the variables significantly affecting the extraction efficiency. Then, the significant factors were more investigated by Box-Behnken design. Calibration curves were linear (R(2)>0.990) in the range of 0.1-1000μgL(-1) for ciprofloxacin (CIP) and 0.5-500μgL(-1) for enrofloxacin (ENR) and ofloxacin (OFL), respectively. LODs for all studied fluoroquinolones ranged from 0.01 to 0.05μgL(-1). The main advantages of this method were rapid and easy automation and analysis, short extraction time, high sensitivity, possibility of fully sorbent collection after analysis, wide linear range and no need to organic solvents in extraction.

  9. Fermionic condensate in a conical space with a circular boundary and magnetic flux

    SciTech Connect

    Bellucci, S.; Bezerra de Mello, E. R.; Saharian, A. A.

    2011-04-15

    The fermionic condensate is investigated in a (2+1)-dimensional conical spacetime in the presence of a circular boundary and a magnetic flux. 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 magnetic flux with the period equal to the flux 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 magnetic flux. 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 magnetic flux to the flux 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 magnetic flux to the flux quantum, the irregular mode gives a nonzero contribution to the fermionic condensate in the boundary-free conical space.

  10. The Formation of Magnetic Depletions and Flux Annihilation Due to Reconnection in the Heliosheath

    NASA Astrophysics Data System (ADS)

    Drake, J. F.; Swisdak, M.; Opher, M.; Richardson, J. D.

    2017-03-01

    The misalignment of the solar rotation axis and the magnetic axis of the Sun produces a periodic reversal of the Parker spiral magnetic 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 magnetic flux 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 flux survive, separated by bands of deep magnetic field depletion. The ambient plasma pressure supports the strong magnetic pressure variation so that pressure is anticorrelated with magnetic field strength. There is little variation in the magnetic field direction across the boundaries of the magnetic depressions. At irregular intervals within the magnetic depressions are long-lived pairs of magnetic islands where the magnetic field direction reverses so that spacecraft data would reveal sharp magnetic field depressions with only occasional crossings with jumps in magnetic field direction. This is typical of the magnetic field data from the Voyager spacecraft. Voyager 2 data reveal that fluctuations in the density and magnetic field strength are anticorrelated in the sector zone, as expected from reconnection, but not in unipolar regions. The consequence of the annihilation of subdominant flux is a sharp reduction in the number of sectors and a loss in magnetic flux, as documented from the Voyager 1 magnetic field and flow data.

  11. 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.

  12. 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.

  13. Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect

    SciTech Connect

    Omidi, Mahboubeh Faizabadi, Edris

    2015-03-21

    Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.

  14. Plasma signatures in large Martian magnetic flux ropes: MARSIS/ASPERA-3 observations

    NASA Astrophysics Data System (ADS)

    Diéval, Catherine; Morgan, David; Duru, Firdevs; Gurnett, Donald

    2014-05-01

    Cylindrical structures of highly twisted magnetic field (flux 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 flux ropes are spikes of magnetic field strength and magnetic field rotations. Both small scale flux ropes (diameters of a few tens of km) and large scale flux ropes (diameters of around 100 km) have been found at Mars. We look at times of presumed flux ropes on the dayside of Mars, detected in the local magnetic field strength given by MARSIS. The signatures in MARSIS are magnetic 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 magnetic field regions. Although we cannot determine the presence of a magnetic field rotation because of the lack of a magnetometer onboard MEX, we assume that these magnetic field increases are large flux ropes. There are indeed large flux ropes with similar characteristics which were established by the magnetometer data from MGS, and thought to form by stretching and reconnection of crustal magnetic 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 flux ropes, which will give hints on their origin.

  15. 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.

  16. Tracking the magnetic structure of flux ropes from eruption to in-situ detection

    NASA Astrophysics Data System (ADS)

    Palmerio, Erika; Kilpua, Emilia; Green, Lucie; James, Alexander; Pomoell, Jens; Valori, Gherardo

    2016-04-01

    Coronal Mass Ejections (CMEs) are spectacular explosions from the Sun where huge amounts of plasma and magnetic flux are ejected into the heliosphere. CMEs are built at the Sun as a force-free (J ×B = 0) magnetic flux rope. It is well-established that CMEs are the main drivers of intense magnetic 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 magnetic fields, neither in the onset process nor during the subsequent propagation from the solar surface to the Earth. The magnetic properties of the CME flux rope (magnetic helicity sign, the flux rope tilt and the direction of the flux 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 flux ropes. We compare their magnetic 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.

  17. Reduction of flux-creep in magnetized bulk HTS by use of permanent magnets

    NASA Astrophysics Data System (ADS)

    Parks, D.; Weinstein, R.; Davey, K.; Sawh, R.-P.; Carpenter, K.

    2017-01-01

    We report the effect of permanent magnet (PM) collars on the flux-creep rate of magnetized 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 flux-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.

  18. Finite element modeling and analysis of electro-magnetic pulse welding of aluminium tubes to steel bars

    NASA Astrophysics Data System (ADS)

    Kumar, Ramesh; Doley, Jyoti; Kore, Sachine

    2016-10-01

    Magnetic pulse welding is a high-speed, solid-state welding process that is applicable to sheets or tube-to-tube or tube-to-bar configurations. In this article we discuss about the MPW process modeling and simulation for welding Al tubes to steel bars. Finite element simulation was done to weld 6061 Al tubes of 1.65 mm wall thickness to 1010 steel bars of a 47.6 mm nominal diameter. Simulation results indicate that Al tubes can be successfully welded to steel bars using MPW. It is found that the standoff distance between the Al tube and the steel bar i.e. gap between inner diameter of Al tube and diameter of steel bar is a dominant factor for achieving a sound weld. The addition of receding angles to the bars can promote MPW weldability window.

  19. 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.

  20. BaBar technical design report: Chapter 9, Magnet coil and flux return

    SciTech Connect

    O`Connor, T.; The BaBar Collaboration

    1995-03-01

    The BaBar magnet is a thin, 1.5 T superconducting solenoid with a hexagonal flux return. This chapter discusses the physics requirements and performance goals for the magnet, describes key interfaces, and summarizes the projected magnet performance. It also presents the design of the superconducting solenoid, including magnetic 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 flux return is described.

  1. 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.

  2. Cluster electric current density measurements within a magnetic flux rope in the plasma sheet

    NASA Technical Reports Server (NTRS)

    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.

    2003-01-01

    On August 22, 2001 all 4 Cluster spacecraft nearly simultaneously penetrated a magnetic flux rope in the tail. The flux 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 flux 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 flux rope moved over the spacecraft is in close agreement with the Cluster plasma measurements. The magnetic field profiles measured at each spacecraft were first modeled separately using the Lepping-Burlaga force-free flux rope model. The results indicated that the center of the flux 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 flux rope predicted by these single-s/c models were approx.15-19 nA/sq m. The 4-spacecraft Cluster magnetic field measurements provide a second means to determine the electric current density without any assumption regarding flux rope structure. The current profile determined using the curlometer technique was qualitatively similar to those determined by modeling the individual spacecraft magnetic 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 flux rope was not force-free with the component of the current density perpendicular to the magnetic 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 flux rope magnetic field and current variations, they do not provide a stringent test of the force-free condition.

  3. Multi-wavelength high-resolution observations of a small-scale emerging magnetic flux event and the chromospheric and coronal response

    SciTech Connect

    Vargas Domínguez, Santiago; Kosovichev, Alexander; Yurchyshyn, Vasyl

    2014-10-20

    State-of-the-art solar instrumentation is now revealing magnetic activity of the Sun with unprecedented temporal and spatial resolutions. Observations with the 1.6 m aperture New Solar Telescope (NST) of the Big Bear Solar Observatory are making next steps in our understanding of the solar surface structure. Granular-scale magnetic flux emergence and the response of the solar atmosphere are among the key research topics of high-resolution solar physics. As part of a joint observing program with NASA's Interface Region Imaging Spectrograph (IRIS) mission on 2013 August 7, the NST observed active region NOAA 11,810 in the photospheric TiO 7057 Å band with a resolution of pixel size of 0.''034 and chromospheric He I 10830 Å and Hα 6563 Å wavelengths. Complementary data are provided by the Solar Dynamics Observatory (SDO) and Hinode space-based telescopes. The region displayed a group of solar pores, in the vicinity of which we detect a small-scale buoyant horizontal magnetic flux tube causing granular alignments and interacting with the preexisting ambient field in the upper atmospheric layers. Following the expansion of distorted granules at the emergence site, we observed a sudden appearance of an extended surge in the He I 10830 Å data (bandpass of 0.05 Å). The IRIS transition region imaging caught ejection of a hot plasma jet associated with the He I surge. The SDO/HMI data used to study the evolution of the magnetic and Doppler velocity fields reveal emerging magnetic loop-like structures. Hinode/Ca II H and IRIS filtergrams detail the connectivities of the newly emerged magnetic field in the lower solar chromosphere. From these data, we find that the orientation of the emerging magnetic field lines from a twisted flux tube formed an angle of ∼45° with the overlying ambient field. Nevertheless, the interaction of emerging magnetic field lines with the pre-existing overlying field generates high-temperature emission regions and boosts the surge

  4. STABILITY AND DYNAMICS OF A FLUX ROPE FORMED VIA FLUX EMERGENCE INTO THE SOLAR ATMOSPHERE

    SciTech Connect

    An, J. M.; Magara, T. E-mail: magara@khu.ac.kr

    2013-08-10

    We study the stability and dynamics of a flux rope formed through the emergence of a twisted magnetic flux tube into the solar atmosphere. A three-dimensional magnetohydrodynamic simulation has been performed to investigate several key factors affecting the dynamics of the flux rope. The stability of the flux rope is examined by deriving the decay index of the coronal magnetic field surrounding the flux rope. We investigate a transition between the quasi-static and dynamic states of the flux rope through an analysis of the curvature and scale height of emerging magnetic field. A practical application of this analysis for global eruptions is also considered.

  5. Magnetically driven flows in arched plasma structures.

    PubMed

    Stenson, E V; Bellan, P M

    2012-08-17

    Laboratory experiments demonstrate high-speed plasma flows from both footpoints of arched magnetic flux tubes, resulting in bulk plasma transport into the flux tube and persistent axial collimation even as the flux tube lengthens and kinks. The measured flows are in agreement with the predictions of hoop force and collimation models involving fundamental MHD forces. These forces are expected to drive plasma acceleration in other open flux configurations with arched geometries, such as those found on the solar surface.

  6. Direct control of air gap flux in permanent magnet machines

    DOEpatents

    Hsu, John S.

    2000-01-01

    A method and apparatus for field weakening in PM machines uses field weakening coils (35, 44, 45, 71, 72) to produce flux in one or more stators (34, 49, 63, 64), including a flux which counters flux 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.

  7. 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.

  8. Observation of an evolving magnetic flux rope before and during a solar eruption.

    PubMed

    Zhang, Jie; Cheng, Xin; Ding, Ming-de

    2012-03-20

    Explosive energy release is a common phenomenon occurring in magnetized plasma systems ranging from laboratories, Earth's magnetosphere, the solar corona and astrophysical environments. Its physical explanation is usually attributed to magnetic reconnection in a thin current sheet. Here we report the important role of magnetic flux rope structure, a volumetric current channel, in producing explosive events. The flux 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 magnetic flux rope triggers the eruption, thus making a major addition to the traditional magnetic-reconnection paradigm.

  9. 22 year cycle in the imbalance of the photospheric magnetic fluxes

    NASA Astrophysics Data System (ADS)

    Vernova, Elena; Baranov, Dmitrii; Tyasto, Marta

    The manifestation of the 22 year solar magnetic cycle in the imbalance of positive and negative photospheric magnetic fluxes is studied. For the analysis we use synoptic maps of the photospheric magnetic field of Kitt Peak Observatory (1976 - 2003) and John Wilcox Observatory in Stanford (1976 - 2012). We consider strong magnetic fields for the heliolatitudes in the interval from +40° to -40°. It is shown that the sign of the imbalance between positive and negative fluxes remains constant during 11 years from one inversion of the Sun’s global magnetic field to the next one and always coincides with the sign of the polar field in the Northern hemisphere. Thus, the imbalance between the magnetic fluxes 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 magnetic fluxes can be observed not only for the strong fields in the sunspot zone. The mean magnetic field of the Sun (Sun as a star), which is determined by the net flux 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 magnetic fields are reflected also in the parameters of heliosphere. We show the connection of the imbalance with the quadrupole component of the photospheric magnetic field and with the imbalance of the interplanetary magnetic field (the difference between the numbers of the days with positive and negative polarities of the interplanetary magnetic field near Earth).

  10. 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.

  11. Mechanical design of ceramic beam tube braze joints for NOvA kicker magnets

    SciTech Connect

    Ader, C.R.; Reilly, R.E.; Wilson, J.H.; /Fermilab

    2010-05-01

    The NO?A Experiment will construct a detector optimized for electron neutrino detection in the existing NuMI neutrino beam. The NuMI beam line is capable of operating at 400 kW of primary beam power and the upgrade will allow up to 700 kW. Ceramic beam tubes are utilized in numerous kicker magnets in different accelerator rings at Fermi National Accelerator Laboratory. Kovar flanges are brazed onto each beam tube end, since kovar and high alumina ceramic have similar expansion curves. The tube, kovar flange, end piece, and braze foil alloy brazing material are stacked in the furnace and then brazed. The most challenging aspect of fabricating kicker magnets in recent years have been making hermetic vacuum seals on the braze joints between the ceramic and flange. Numerous process variables can influence the robustness of conventional metal/ceramic brazing processes. The ceramic-filler metal interface is normally the weak layer when failure does not occur within the ceramic. Differences between active brazing filler metal and the moly-manganese process will be discussed along with the applicable results of these techniques used for Fermilab production kicker tubes.

  12. A portable magnetic field of >3 T generated by the flux jump assisted, pulsed field magnetization of bulk superconductors

    NASA Astrophysics Data System (ADS)

    Zhou, Difan; Ainslie, Mark D.; Shi, Yunhua; Dennis, Anthony R.; Huang, Kaiyuan; Hull, John R.; Cardwell, David A.; Durrell, John H.

    2017-02-01

    A trapped magnetic 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 magnetization. The magnet system is portable and operates at temperatures between 50 K and 60 K. Flux jump behaviour was observed consistently during magnetization 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 flux jump behaviour enables the magnetic flux to penetrate fully to the centre of the bulk superconductor, resulting in full magnetization of the sample without requiring an applied field as large as that predicted by the Bean model. We show that this flux jump behaviour can occur over a wide range of fields and temperatures, and that it can be exploited in a practical quasi-permanent magnet system.

  13. Magnetic flux and heat losses by diffusive, advective, and Nernst effects in magnetized liner inertial fusion-like plasma

    SciTech Connect

    Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.

    2015-04-15

    The magnetized 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 magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic 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 magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux 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 magnetic flux 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.

  14. Magnetic flux and heat losses by diffusive, advective, and Nernst effects in magnetized liner inertial fusion-like plasma

    NASA Astrophysics Data System (ADS)

    Velikovich, A. L.; Giuliani, J. L.; Zalesak, S. T.

    2015-04-01

    The magnetized 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 magnetic flux by a heavy cylindrical liner. The losses of heat and magnetic flux from the plasma to the liner are thereby determined by plasma advection and gradient-driven transport processes, such as thermal conductivity, magnetic 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 magnetized plasma to the cold liner is dominated by transverse heat conduction and advection, and the corresponding loss of magnetic flux 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 magnetic flux 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.

  15. Silica supported Fe(3)O(4) magnetic nanoparticles for magnetic solid-phase extraction and magnetic in-tube solid-phase microextraction: application to organophosphorous compounds.

    PubMed

    Moliner-Martinez, Y; Vitta, Yosmery; Prima-Garcia, Helena; González-Fuenzalida, R A; Ribera, Antonio; Campíns-Falcó, P; Coronado, Eugenio

    2014-03-01

    This work demonstrates the application of silica supported Fe3O4 nanoparticles as sorbent phase for magnetic solid-phase extraction (MSPE) and magnetic on-line in-tube solid-phase microextraction (Magnetic-IT-SPME) combined with capillary liquid chromatography-diode array detection (CapLC-DAD) to determine organophosphorous compounds (OPs) at trace level. In MSPE, magnetism is used as separation tool while in Magnetic-IT-SPME, the application of an external magnetic field gave rise to a significant improvement of the adsorption of OPs on the sorbent phase. Extraction efficiency, analysis time, reproducibility and sensitivity have been compared. This work showed that Magnetic-IT-SPME can be extended to OPs with successful results in terms of simplicity, speed, extraction efficiency and limit of detection. Finally, wastewater samples were analysed to determine OPs at nanograms per litre.

  16. 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.

  17. Positron emission tomography within a magnetic field using photomultiplier tubes and lightguides.

    PubMed

    Christensen, N L; Hammer, B E; Heil, B G; Fetterly, K

    1995-04-01

    The spatial resolution of positron emission tomography (PET) improves when positron annihilation takes place in a strong magnetic field. In a magnetic field, the Lorentz force restricts positron range perpendicular to the field. Since positron annihilation occurs closer to its point of origin, the positron annihilation point spread function decreases. This was verified experimentally by measuring the spread function of positron annihilation from a 500 mm 68Ge bead imbedded in tissue-equivalent wax. At 5 T the spread function full width at half maximum (FWHM) and the full width at tenth maximum (FWTM) decrease by a factor of 1.42 and 2.09, respectively. Two NaI(Tl) scintillation crystals that interface to a pair of photomultiplier tubes (PMTS) through long lightguides detect positron annihilation at zero field and 5.0 T. Photomultiplier tubes, inoperable in strong magnetic fields, are functional if lightguides bring the photons produced by scintillators within the field to a minimal magnetic field. These tests also demonstrate techniques necessary for combining magnetic resonance imaging (MRI) and PET into one scanner.

  18. A phenomenological model for boiling heat transfer and the critical heat flux in tubes containing twisted tapes

    NASA Astrophysics Data System (ADS)

    Weisman, J.; Yang, J. Y.; Usman, S.

    1994-01-01

    New critical heat flux (CHF) and boiling heat transfer data were obtained in the subcooled and low quality regions using refrigerant 113. These data were obtained in a 0.61 cm round tube containing a twisted tape having a twist ratio of 6.25. The new CHF data, plus water data from the literature, were compared to a modified version of the CHF predictive model based on bubble crowding and coalescence in the bubbly layer (Weisman and Pei, (1983), Weisman and Illeslamlou, (1988)). Reasonably good predictions were obtained within the range of the model. It was also found that the Yang and Weisman (1991) extension of the CHF model to boiling heat transfer held for swirling flow.

  19. Drift flux model as approximation of two fluid model for two phase dispersed and slug flow in tube

    SciTech Connect

    Nigmatulin, R.I.

    1995-09-01

    The analysis of one-dimensional schematizing for non-steady two-phase dispersed and slug flow in tube is presented. Quasi-static approximation, when inertia forces because of the accelerations of the phases may be neglected, is considered. Gas-liquid bubbly and slug vertical upward flows are analyzed. Non-trivial theoretical equations for slip velocity for these flows are derived. Juxtaposition of the derived equations for slip velocity with the famous Zuber-Findlay correlation as cross correlation coefficients is criticized. The generalization of non-steady drift flux Wallis theory taking into account influence of wall friction on the bubbly or slug flows for kinematical waves is considered.

  20. A Magnetic Flux Leakage and Magnetostrictive Guided Wave Hybrid Transducer for Detecting Bridge Cables

    PubMed Central

    Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

    2012-01-01

    Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux 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 magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic 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

  1. A magnetic flux leakage and magnetostrictive guided wave hybrid transducer for detecting bridge cables.

    PubMed

    Xu, Jiang; Wu, Xinjun; Cheng, Cheng; Ben, Anran

    2012-01-01

    Condition assessment of cables has gained considerable attention for the bridge safety. A magnetic flux 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 magnetizers and a ribbon coil. The static axial magnetic field provided by the magnetizers meets the needs of the magnetic flux leakage testing and the magnetostrictive guided wave testing. The magnetizers also provide the attraction for the climbing modules. In the magnetic flux leakage testing for the free length of cable, the coil induces the axial leakage magnetic field. In the magnetostrictive guided wave testing for the anchorage zone, the coil provides a pulse high power variational magnetic field for generating guided waves; the coil induces the magnetic 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.

  2. MAGNETAR GIANT FLARES-FLUX ROPE ERUPTIONS IN MULTIPOLAR MAGNETOSPHERIC MAGNETIC FIELDS

    SciTech Connect

    Yu Cong

    2012-09-20

    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 magnetic field configurations that contain a helically twisted force-free flux rope. Depending on the surface magnetic field polarity, there exist two kinds of magnetic field configurations, inverse and normal. For these two kinds of configurations, variations of the flux rope equilibrium height in response to gradual surface physical processes, such as flux 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 magnetic field evolves slowly, the height of the flux rope would gradually reach a critical value beyond which stable equilibriums can no longer be maintained. Subsequently, the flux rope would lose equilibrium and the gradual quasi-static evolution of the magnetosphere will be replaced by a fast dynamical evolution. In addition to flux injections, the relative motion of active regions would give rise to the catastrophic behavior and lead to magnetic 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.

  3. Coalescence of magnetic flux ropes observed in the tailward high-speed flows

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Wang, Rongsheng; Lu, Quanming; Du, Aimin; Yao, Zhonghua; Wu, Mingyu

    2016-11-01

    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 magnetic flux ropes, while the middle one is found to result from the collision of the two flux 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 magnetic flux ropes were coalescing. The observations indicate that coalescence of magnetic flux 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.

  4. Induced fermionic current by a magnetic flux in a cosmic string spacetime at finite temperature

    NASA Astrophysics Data System (ADS)

    Bezerra de Mello, Eugênio R.; Saharian, Aram A.; Mohammadi, Azadeh

    2016-01-01

    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 magnetic flux 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 magnetic flux with the period equal to the quantum flux 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 magnetic flux 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.

  5. 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.

  6. Magnetic flux relaxation in YBa2Cu3)(7-x) thin film: Thermal or athermal

    NASA Technical Reports Server (NTRS)

    Vitta, Satish; Stan, M. A.; Warner, J. D.; Alterovitz, S. A.

    1991-01-01

    The magnetic flux 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 flux relaxation rate S and the net flux 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 flux 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 flux lines. The magnetic field dependence of U, however, is not completely understood.

  7. Line-Tied Magnetic Flux Ropes in the Laboratory: Equilibrium Force Balance and Eruptive Instabilities

    NASA Astrophysics Data System (ADS)

    Myers, Clayton E.; Yamada, M.; Belova, E. V.

    2013-07-01

    Flux-rope-based models of solar eruptions rely on the formation of a line-tied flux 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 flux ropes, focusing primarily on the role of the potential magnetic field in controlling the flux 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 flux ropes studied here, which are produced in the Magnetic 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 magnetic field configuration that can be systematically modified between discharges. Detailed in situ magnetic 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 flux ropes are often well confined even in the absence of a "strapping" arcade. These observed guide field forces arise from changes in the toroidal magnetic pressure and tension that result from a combination of effects within the expanding flux rope. With regard to eruptions, the aforementioned guide field forces supplement the well-known strapping field forces to largely prevent the flux ropes from erupting. In particular, many regimes were explored where the strapping field configuration is predicted to be "torus unstable" and yet the flux ropes do not erupt. Eruptions are observed in some regimes, however, and we will discuss the physical

  8. Laboratory simulation of arched magnetic flux rope eruptions in the solar atmosphere.

    PubMed

    Tripathi, S K P; Gekelman, W

    2010-08-13

    Dramatic eruption of an arched magnetic flux 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 magnetic-field topology and link the magnetic-field lines of the rope with the ambient plasma. Following this event, the flux 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.

  9. Laboratory Simulation of Arched Magnetic Flux Rope Eruptions in the Solar Atmosphere

    SciTech Connect

    Tripathi, S. K. P.; Gekelman, W.

    2010-08-13

    Dramatic eruption of an arched magnetic flux 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 magnetic-field topology and link the magnetic-field lines of the rope with the ambient plasma. Following this event, the flux 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.

  10. Magnetic flux transport and the sun's dipole moment - New twists to the Babcock-Leighton model

    NASA Technical Reports Server (NTRS)

    Wang, Y.-M.; Sheeley, N. R., Jr.

    1991-01-01

    The mechanisms that give rise to the sun's large-scale poloidal magnetic 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 magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed.

  11. Embedding Circular Force-Free Flux Ropes in Potential Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.

    2013-12-01

    We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type magnetic field with a thin force-free flux rope embedded inside it. The flux rope has a circular-arc axis and circular cross-section in which the interior magnetic field is predominantly toroidal (axial). Its magnetic pressure is balanced outside by that of the poloidal (azimuthal) field created at the boundary by the electric current sheathing the flux 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 magnetic field. The parameters of the flux 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 magnetic configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the flux rope. The proposed method is a useful tool for constructing pre-eruption magnetic 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.

  12. Magnetism-Enhanced Monolith-Based In-Tube Solid Phase Microextraction.

    PubMed

    Mei, Meng; Huang, Xiaojia; Luo, Qing; Yuan, Dongxin

    2016-02-02

    Monolith-based in-tube solid phase microextraction (MB/IT-SPME) has received wide attention because of miniaturization, automation, expected loading capacity, and environmental friendliness. However, the unsatisfactory extraction efficiency becomes the main disadvantage of MB/IT-SPME. To overcome this circumstance, magnetism-enhanced MB/IT-SPME (ME-MB/IT-SPME) was developed in the present work, taking advantage of magnetic microfluidic principles. First, modified Fe3O4 nanoparticles were mixed with polymerization solution and in situ polymerized in the capillary to obtain a magnetic monolith extraction phase. After that, the monolithic capillary column was placed inside a magnetic coil that allowed the exertion of a variable magnetic field. The effects of intensity of magnetic field, adsorption and desorption flow rate, volume of sample, and desorption solvent on the performance of ME-MB/IT-SPME were investigated in detail. The analysis of six steroid hormones in water samples by the combination of ME-MB/IT-SPME with high-performance liquid chromatography with diode array detection was selected as a paradigm for the practical evaluation of ME-MB/IT-SPME. The application of a controlled magnetic field resulted in an obvious increase of extraction efficiencies of the target analytes between 70% and 100%. The present work demonstrated that application of different magnetic forces in adsorption and desorption steps can effectively enhance extraction efficiency of MB/IT-SPME systems.

  13. Skin-layer of the eruptive magnetic flux rope in large solar flares

    NASA Astrophysics Data System (ADS)

    Kichigin, G. N.; Miroshnichenko, L. I.; Sidorov, V. I.; Yazev, S. A.

    2016-07-01

    The analysis of observations of large solar flares made it possible to propose a hypothesis on existence of a skin-layer in magnetic flux ropes of coronal mass ejections. On the assumption that the Bohm coefficient determines the diffusion of magnetic 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 magnetic field of flux rope, arises for ~5 min in the surface layer of the eruptive flux 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 flux rope leads to their precipitation along field lines to footpoints of the flux 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 magnetic reconnection in the corona leads to a shift of the skin-layer of flux rope across the magnetic field. The area of precipitation of accelerated particles at the flux-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 magnetic barrier (in the magnetic 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.

  14. Supersymmetric models on magnetized orbifolds with flux-induced Fayet-Iliopoulos terms

    NASA Astrophysics Data System (ADS)

    Abe, Hiroyuki; Kobayashi, Tatsuo; Sumita, Keigo; Tatsuta, Yoshiyuki

    2017-01-01

    We study supersymmetric (SUSY) models derived from the ten-dimensional SUSY Yang-Mills theory compactified on magnetized orbifolds, with nonvanishing Fayet-Iliopoulos (FI) terms induced by magnetic fluxes in extra dimensions. Allowing the presence of FI-terms relaxes a constraint on flux configurations in SUSY model building based on magnetized backgrounds. In this case, charged fields develop their vacuum expectation values to cancel the FI-terms in the D-flat directions of fluxed gauge symmetries, which break the gauge symmetries and lead to a SUSY vacuum. Based on this idea, we propose a new class of SUSY magnetized 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.

  15. Twist accumulation and topology structure of a solar magnetic flux rope

    SciTech Connect

    Guo, Y.; Ding, M. D.; Cheng, X.; Zhao, J.; Pariat, E.

    2013-12-20

    To study the buildup of a magnetic flux rope before a major flare and coronal mass ejection (CME), we compute the magnetic helicity injection, twist accumulation, and topology structure of the three-dimensional (3D) magnetic 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 magnetic fields, which were observed by the Digital Vector Magnetograph at Big Bear Solar Observatory. The injected magnetic helicity is computed with the vector magnetic 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 magnetic helicity became the internal helicity of the magnetic flux rope, whose twist increasing rate was –0.18 ± 0.08 Turns hr{sup –1}. The quasi-separatrix layers (QSLs) of the 3D magnetic field are computed by evaluating the squashing degree, Q. We find that the flux rope was wrapped by QSLs with large Q values, where the magnetic reconnection induced by the continuously injected magnetic helicity further produced the confined flares. We suggest that the flux rope was built up and heated by the magnetic reconnection in the QSLs.

  16. Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems

    SciTech Connect

    He, Jianliang; Coffey, H.

    1997-08-01

    This paper discusses magnetic damping forces in figure-eight-shaped null-flux coil suspension systems, focusing on the Holloman maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting magnet by two short-circuited loop coils in the guideway. Closed-form formulas for the magnetic 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.

  17. The Depolarization Probability of Ultracold Neutrons in Collision with Material Guide Tubes in a Varying Ambient Magnetic Field

    NASA Astrophysics Data System (ADS)

    Dearmitt, Damien; Holley, Adam

    2016-09-01

    Ultracold neutrons (UCN) are defined as having an energy of 100 neV. Polarized β-decay experiments using UCN require consideration of material depolarization for maximizing statistics as well as for understanding and controlling systematic effects. The Los Alamos National Lab UCN team performed an experiment in which UCN were polarized using a 6T longitudinal field. The resulting high-field-seeking spin state neutrons were then introduced into a material test guide. UCN which depolarize become trapped between the high-field region and a shutter, while high-field seeking UCN return through the magnet and are upscattered on a plastic foil. After loading the system with UCN and monitoring the incoming flux, the depolarization probability per bounce can be determined by opening the shutter and counting the population of trapped depolarized neutrons. A determination from this dataset of depolarization per bounce as a function of the ambient magnetic field in guide tubes made of unpolished, mechanically polished, and electropolished Cu, diamond-like carbon coated Cu, and stainless steel will be presented.

  18. Observations and analysis of small-scale magnetic flux ropes in the solar wind

    NASA Astrophysics Data System (ADS)

    Zheng, Jinlei; Hu, Qiang

    2016-11-01

    The small-scale magnetic flux 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 flux ropes, i.e., magnetic clouds. However, accumulating evidence suggests that their plasma characteristics, origin, formation mechanism and evolution are different from those of large-scale flux ropes. The small-scale flux 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 flux rope structures in two events using the Grad-Shafranov reconstruction approach. In one event, a twin flux rope structure at 1 AU occurring on 2002 February 1 and two following single flux rope structures are identified behind an interplanetary shock. In the other event, we reconstruct the flux 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 flux rope structures are discussed.

  19. 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

  20. Magnetic Flux Ropes from the Sun to 1 AU*

    NASA Astrophysics Data System (ADS)

    Krall, J.; Yurchyshyn, V. B.; St. Cyr, O. C.; Chen, J.

    2004-12-01

    Any practical model of the dynamics of a coronal mass ejection (CME) and its interplanetary counterpart (ICME) must conform to available observational constraints from sun and to the earth; the upcoming STEREO mission will add significantly to those constraints. We present model/data comparisons for specific CME/ICME events near the sun (using coronagraph image data) and in the heliosphere (using in situ measurements) to show that the flux rope model of Chen and Krall[1-2] provides an accurate physics-based characterization of flux-rope CMEs over this range. We further show that quantitative results, such as the field energy required for eruption, depend on specific aspects of the flux rope geometry, such as the ratio (length/width) of the elliptical shape traced out by the flux-rope axis. It is this geometry that will be determined, for the first time, by STEREO. [1] Chen, J. 1996, JGR, 101, 27499 [2] Krall, J. et al., 2000, ApJ, 539, 964 *Work supported by ONR, NASA and NSF

  1. Improved thrust calculations of active magnetic bearings considering fringing flux

    NASA Astrophysics Data System (ADS)

    Jang, Seok-Myeong; Kim, Kwan-Ho; Ko, Kyoung-Jin; Choi, Ji-Hwan; Sung, So-Young; Lee, Yong-Bok

    2012-04-01

    A methodology for deriving fringing permeance in axisymmetric devices such as active thrust magnetic bearings (ATMBs) is presented. The methodology is used to develop an improved equivalent magnetic circuit (EMC) for ATMBs, which considers the fringing effect. This EMC was used to characterize the force between the housing and mover and the dependence of thrust and inductance on the air gap and input current, respectively. These characteristics were validated by comparison with those obtained by the finite element method and in experiments.

  2. On Polar Magnetic Field Reversal and Surface Flux Transport During Solar Cycle 24

    NASA Astrophysics Data System (ADS)

    Sun, Xudong; Hoeksema, J. Todd; Liu, Yang; Zhao, Junwei

    2015-01-01

    As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33-2014.33) of line-of-sight magnetic field measurements from the Helioseismic and Magnetic Imager. The total flux associated with ARs reached maximum in the north in 2011, more than two years earlier than the south; the maximum is significantly weaker than Cycle 23. The process of polar field reversal is relatively slow, north-south asymmetric, and episodic. We estimate that the global axial dipole changed sign in 2013 October; the northern and southern polar fields (mean above 60° latitude) reversed in 2012 November and 2014 March, respectively, about 16 months apart. Notably, the poleward surges of flux in each hemisphere alternated in polarity, giving rise to multiple reversals in the north. We show that the surges of the trailing sunspot polarity tend to correspond to normal mean AR tilt, higher total AR flux, or slower mid-latitude near-surface meridional flow, while exceptions occur during low magnetic activity. In particular, the AR flux and the mid-latitude poleward flow speed exhibit a clear anti-correlation. We discuss how these features can be explained in a surface flux transport process that includes a field-dependent converging flow toward the ARs, a characteristic that may contribute to solar cycle variability.

  3. ON POLAR MAGNETIC FIELD REVERSAL AND SURFACE FLUX TRANSPORT DURING SOLAR CYCLE 24

    SciTech Connect

    Sun, Xudong; Todd Hoeksema, J.; Liu, Yang; Zhao, Junwei

    2015-01-10

    As each solar cycle progresses, remnant magnetic flux from active regions (ARs) migrates poleward to cancel the old-cycle polar field. We describe this polarity reversal process during Cycle 24 using four years (2010.33-2014.33) of line-of-sight magnetic field measurements from the Helioseismic and Magnetic Imager. The total flux associated with ARs reached maximum in the north in 2011, more than two years earlier than the south; the maximum is significantly weaker than Cycle 23. The process of polar field reversal is relatively slow, north-south asymmetric, and episodic. We estimate that the global axial dipole changed sign in 2013 October; the northern and southern polar fields (mean above 60° latitude) reversed in 2012 November and 2014 March, respectively, about 16 months apart. Notably, the poleward surges of flux in each hemisphere alternated in polarity, giving rise to multiple reversals in the north. We show that the surges of the trailing sunspot polarity tend to correspond to normal mean AR tilt, higher total AR flux, or slower mid-latitude near-surface meridional flow, while exceptions occur during low magnetic activity. In particular, the AR flux and the mid-latitude poleward flow speed exhibit a clear anti-correlation. We discuss how these features can be explained in a surface flux transport process that includes a field-dependent converging flow toward the ARs, a characteristic that may contribute to solar cycle variability.

  4. 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.

  5. Relaxation of flux ropes and magnetic reconnection in the Reconnection Scaling Experiment at LANL

    NASA Astrophysics Data System (ADS)

    Furno, Ivo

    2004-11-01

    Magnetic reconnection and plasma relaxation are studied in the Reconnection Scaling Experiment (RSX) with current carrying plasma columns (magnetic flux ropes). Using plasma guns, multiple flux ropes (B_pol < 100 Gauss, L=90 cm, r < 3 cm) are generated in a three-dimensional (3D) cylindrical geometry and are observed to evolve dynamically during the injection of magnetic helicity. Detailed evolution of electron density, temperature, plasma potential and magnetic field structures is reconstructed experimentally and visible light emission is captured with a fast-gated, intensified CCD camera to provide insight into the global flux rope dynamics. Experiments with two flux ropes in collisional plasmas and in a strong axial guide field (Bz / B_pol > 10) suggest that magnetic reconnection plays an important role in the initial stages of flux rope evolution. During the early stages of the applied current drive (t < 20τ_Alfven), the flux ropes are observed to twist, partially coalesce and form a thin current sheet with a scale size comparable to that of the ion sound gyro-radius. Here, non-ideal terms in a generalized Ohm's Law appear to play a significant role in the 3D reconnection process as shown by the presence of a strong axial pressure gradient in the current sheet. In addition, a density perturbation with a structure characteristic of a kinetic Alfvén wave is observed to propagate axially in the current layer, anti-parallel to the induced sheet current. Later in the evolution, when a sufficient amount of helicity is injected into the system, a critical threshold for the kink instability is exceeded and the helical twisting of each individual flux rope can dominate the dynamics of the system. This may prevent the complete coalescence of the flux ropes.

  6. Relaxation of flux ropes and magnetic reconnection in the Reconnection Scaling Experiment at LANL

    NASA Astrophysics Data System (ADS)

    Furno, I.; Intrator, T.; Hemsing, E.; Hsu, S.; Lapenta, G.; Abbate, S.

    2004-12-01

    Magnetic reconnection and plasma relaxation are studied in the Reconnection Scaling Experiment (RSX) with current carrying plasma columns (magnetic flux ropes). Using plasma guns, multiple flux ropes (Bθ ≤ 100 Gauss, L=90 cm, r≤3 cm) are generated in a three-dimensional (3D) cylindrical geometry and are observed to evolve dynamically during the injection of magnetic helicity. Detailed evolution of electron density, temperature, plasma potential and magnetic field structures is reconstructed experimentally and visible light emission is captured with a fast-gated, intensified CCD camera to provide insight into the global flux rope dynamics. Experiments with two flux ropes in collisional plasmas and in a strong axial guide field (Bz / Bθ > 10) suggest that magnetic reconnection plays an important role in the initial stages of flux rope evolution. During the early stages of the applied current drive (t≤ 20 τ Alfv´ {e}n), the flux ropes are observed to twist, partially coalesce and form a thin current sheet with a scale size comparable to that of the ion sound gyro-radius. Here, non-ideal terms in a generalized Ohm's Law appear to play a significant role in the 3D reconnection process as shown by the presence of a strong axial pressure gradient in the current sheet. In addition, a density perturbation with a structure characteristic of a kinetic Alfvén wave is observed to propagate axially in the current layer, anti-parallel to the induced sheet current. Later in the evolution, when a sufficient amount of helicity is injected into the system, a critical threshold for the kink instability is exceeded and the helical twisting of each individual flux rope can dominate the dynamics of the system. This may prevent the complete coalescence of the flux ropes.

  7. Magnetic flux conversion in the DIII-D high-beta hybrid scenario

    NASA Astrophysics Data System (ADS)

    Taylor, N. Z.; Luce, T. C.; La Haye, R. J.; Petty, C. C.; Piovesan, P.

    2016-10-01

    In DIII-D hybrid scenario discharges, the rate of poloidal magnetic energy consumption is more than the rate of energy flow from the poloidal field coils. This is evidence that there is a conversion of toroidal flux to poloidal flux, which may account for a process known as flux pumping that leads to anomalous broadening of the current profile. The hybrid is a promising high confinement scenario for ITER. The broader current profile aids discharge sustainment by raising the minimum safety factor above unity thereby avoiding sawtooth-triggered 2/1 tearing modes that spoil energy confinement. During long ( 1.5s) stationary intervals with constant stored magnetic energy, a significant flux state deficit rate >10 mV was observed. This anomalous consumption of poloidal flux only occurred in discharges with βN > 2.5 and when a relatively benign 3/2 tearing mode was present. This suggests the tearing mode plays a critical role in flux conversion. Studies have shown that 3D core displacements can lead to flux conversion, suggesting that the 3/2 tearing mode and its 2/2 side band produce helical perturbations in the core velocity and magnetic field capable of producing a dynamo EMF that drives the observed current redistribution. Supported by the US DOE under DE-AC05-06OR23100 and DE-FC02-04ER54698.

  8. Enhancement of critical heat flux for subcooled flow boiling of water in tubes with a twisted tape and with a helically coiled wire

    SciTech Connect

    Kabata, Y.; Nakajima, R.; Shioda, K.

    1996-08-01

    This paper reports results of an experimental investigation for critical heat flux (CHF) up to 30 MW/m{sup 2} in subcooled flow boiling of water in tubes with a twisted tape and with a helically coiled wire. Experiments were carried out using uniformly heated horizontal tubes with inner diameters of 8 and 12 mm, and with a heated length of 50 mm. Although the CHF of tubes with and without the twisted tape depends on velocity and exit subcooling of water, no observable influence of the tube diameter is detected. As for the CHF enhancement ratio of the tubes with the tape, it is at least 40% higher than the case without the tape, and increases as the exit water subcooling decreases. In the case of the helically coiled wire, the CHF increases as the wire diameter becomes larger and as the coil pitch smaller. The increase of the CHF by the coil, which is the wire diameter of 1.0 mm and the coil pitch of 12 mm, is higher than that by the twisted tape. The CHF model for the smooth tube developed by Celata et al. was applied to the swirl tube by modifying for the calculation of the friction factor, and the radial temperature and velocity distribution in the liquid. Prediction using the modified Celata model accounts for almost all available experimental data for the swirl tube within {+-}25%. This study is relevant for the development of fusion reactors.

  9. Tunable magnetic flux sensor using a metallic Rashba ring with half-metal electrodes

    NASA Astrophysics Data System (ADS)

    Chen, J.; Jalil, M. B. A.; Tan, S. G.

    2011-04-01

    We propose a magnetic field sensor consisting of a square ring made of metal with a strong Rashba spin-orbital coupling (RSOC) and contacted to half-metal electrodes. Due to the Aharonov-Casher effect, the presence of the RSOC imparts a spin-dependent geometric phase to conduction electrons in the ring. The combination of the magnetic flux emanating from the magnetic sample placed below the ring, and the Aharonov-Casher effect due to RSOC results in spin interference, which modulates the spin transport in the ring nanostructure. By using the tight-binding nonequilibrium Green's function formalism to model the transport across the nanoring detector, we theoretically show that with proper optimization, the Rashba ring can function as a sensitive and tunable magnetic probe to detect magnetic flux.

  10. Origin and Reduction of 1 /f Magnetic Flux Noise in Superconducting Devices

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Sendelbach, S.; Beck, M. A.; Freeland, J. W.; Wang, Zhe; Wang, Hui; Yu, Clare C.; Wu, R. Q.; Pappas, D. P.; McDermott, R.

    2016-10-01

    Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1 /fα, with α ≲1 , and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular O2 is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be reduced by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more than an order of magnitude and a suppression of 1 /f magnetic flux noise power spectral density of up to a factor of 5. These advances open the door to the realization of superconducting qubits with improved quantum coherence.

  11. 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.

  12. Permanent magnet desktop magnetic resonance imaging system with microfabricated multiturn gradient coils for microflow imaging in capillary tubes.

    PubMed

    Sahebjavaher, Ramin S; Walus, Konrad; Stoeber, Boris

    2010-02-01

    A prototype for a desktop high-resolution magnetic resonance imaging (MRI) velocimetry instrument to characterize flow fields in a capillary tube is demonstrated. This inexpensive compact system is achieved with a 0.6 T permanent magnetic configuration (Larmor frequency of 25 MHz) and temperature compensation using off-the-shelf NdFeB permanent magnets. A triaxial gradient module with microfabricated copper coils using a lithographic fabrication process has been developed. This gradient module is capable of generating fast-switching gradients (<100 micros) with amplitudes up to 1.7 T/m using custom made current amplifiers, and was optimized for microflow imaging. The radio frequency probe is integrated with the gradient module and is driven by custom electronics. A two-dimensional (2D) cross-sectional static image of the inside of a capillary tube with an inner diameter of 1.67 mm is acquired at an in-plane spatial resolution of better than 40 microm. Time-of-flight flow measurements were also obtained using this MRI system to measure the velocity profile of water flowing at average velocities of above 50 mm/s. The flow profile for slower flow velocities was obtained using phase-encoded techniques, which provides quantitative velocity information in 2D.

  13. Longitudinal and seasonal variation of the equatorial flux tube integrated Rayleigh-Taylor instability growth rate

    NASA Astrophysics Data System (ADS)

    Wu, Qian

    2015-09-01

    Using the National Center for Atmospheric Research Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM), the ionospheric Rayleigh-Taylor instability growth rate is calculated. The seasonal and longitudinal variations of the growth rate from the TIEGCM appear to match that of the spread F observed by various satellite missions. The growth rate is strongly dependent on the angle between the sunset terminator and the geomagnetic field line near the magnetic equator. The TIEGCM simulations with nonmigrating tides show the zonal wave number 4 structure in the Rayleigh-Taylor instability due to the inclusion of the nonmigrating diurnal eastward zonal wave number 3 and semidiurnal eastward zonal wave number 2 tides.

  14. Effect of different magnetic field distributions on laminar ferroconvection heat transfer in horizontal tube

    NASA Astrophysics Data System (ADS)

    Sheikhnejad, Yahya; Hosseini, Reza; Saffar-avval, Majid

    2015-09-01

    The forced convection heat transfer of ferrofluid steady state laminar flow through a circular axisymmetric horizontal pipe under different magnetic field is the focus of this study. The pipe is under constant heat flux while different linear axial magnetic fields were applied on the ferrofluid with equal magnetic energy. In this scenario, viscosity of ferrofluid is temperature dependent, to capture ferrofluid real behavior a nonlinear Langevin equation was considered for equilibrium magnetization. For this purpose, the set of nonlinear governing PDEs was solved using proper CFD techniques: the finite volume method and SIMPLE algorithm were used to discretize and numerically solve the governing equation in order to obtain thermohydrodynamic flow characteristics. The numerical results show a promising enhancement of up to 135.7% in heat transfer as a consequence of the application of magnetic field. The magnetic field also increases pressure loss of up to 77% along the pipe; but effectiveness (favorable to unfavorable effect ratio) of the magnetic field as a performance index economically justifies its application such that higher magnetic field intensity causes higher effectiveness of up to 1.364.

  15. The effect of magnetic field on nanofluids heat transfer through a uniformly heated horizontal tube

    NASA Astrophysics Data System (ADS)

    Hatami, N.; Kazemnejad Banari, A.; Malekzadeh, A.; Pouranfard, A. R.

    2017-02-01

    In this study, the effects of magnetic field on forced convection heat transfer of Fe3O4-water nanofluid with laminar flow regime in a horizontal pipe under constant heat flux conditions were studied, experimentally. The convective heat transfer of magnetic fluid flow inside the heated pipe with uniform magnetic field was measured. Fe3O4 nanoparticles with diameters less than 100 nm dispersed in water with various volume concentrations are used as the test fluid. The effect of the external magnetic field (Ha = 33.4 ×10-4 to 136.6 ×10-4) and nanoparticle concentrations (φ = 0, 0.1, 0.5, 1%) on heat transfer characteristics were investigated. Results showed that by the presence of a magnetic field, increase in nanoparticle concentration caused reduction of convection heat transfer coefficient. In this condition, heat transfer decreased up to 25%. Where, in the absence of an external magnetic field, adding magnetic nanoparticles increased convection heat transfer more than 60%. It was observed that the Nusselt number decreased by increasing the Hartmann number at a specified concentration of magnetic nanofluids, that reduction about 25% in heat transfer rate could be found.

  16. Magnetic microscopic imaging with an optically pumped magnetometer and flux guides

    NASA Astrophysics Data System (ADS)

    Kim, Young Jin; Savukov, Igor; Huang, Jen-Huang; Nath, Pulak

    2017-01-01

    By combining an optically pumped magnetometer (OPM) with flux guides (FGs) and by installing a sample platform on automated translation stages, we have implemented an ultra-sensitive FG-OPM scanning magnetic imaging system that is capable of detecting magnetic fields of ˜20 pT with spatial resolution better than 300 μm (expected to reach ˜10 pT sensitivity and ˜100 μm spatial resolution with optimized FGs). As a demonstration of one possible application of the FG-OPM device, we conducted magnetic imaging of micron-size magnetic particles. Magnetic imaging of such particles, including nano-particles and clusters, is very important for many fields, especially for medical cancer diagnostics and biophysics applications. For rapid, precise magnetic imaging, we constructed an automatic scanning system, which holds and moves a target sample containing magnetic particles at a given stand-off distance from the FG tips. We show that the device was able to produce clear microscopic magnetic images of 10 μm-size magnetic particles. In addition, we also numerically investigated how the magnetic flux from a target sample at a given stand-off distance is transmitted to the OPM vapor cell.

  17. Magnetic microscopic imaging with an optically pumped magnetometer and flux guides

    DOE PAGES

    Kim, Young Jin; Savukov, Igor Mykhaylovich; Huang, Jen -Huang; ...

    2017-01-23

    Here, by combining an optically pumped magnetometer (OPM) with flux guides (FGs) and by installing a sample platform on automated translation stages, we have implemented an ultra-sensitive FG-OPM scanning magnetic imaging system that is capable of detecting magnetic fields of ~20 pT with spatial resolution better than 300 μm (expected to reach ~10 pT sensitivity and ~100 μm spatial resolution with optimized FGs). As a demonstration of one possible application of the FG-OPM device, we conducted magnetic imaging of micron-size magnetic particles. Magnetic imaging of such particles, including nano-particles and clusters, is very important for many fields, especially for medicalmore » cancer diagnostics and biophysics applications. For rapid, precise magnetic imaging, we constructed an automatic scanning system, which holds and moves a target sample containing magnetic particles at a given stand-off distance from the FG tips. We show that the device was able to produce clear microscopic magnetic images of 10 μm-size magnetic particles. In addition, we also numerically investigated how the magnetic flux from a target sample at a given stand-off distance is transmitted to the OPM vapor cell.« less

  18. A flux-mnemonic permanent magnet brushless machine for wind power generation

    NASA Astrophysics Data System (ADS)

    Yu, Chuang; Chau, K. T.; Jiang, J. Z.

    2009-04-01

    In this paper, the concept of flux mnemonics is newly extended to the wind power generator. By incorporating a small magnetizing winding into an outer-rotor doubly salient AlNiCo permanent magnet (PM) machine, a new flux-mnemonic PM brushless wind power generator is proposed and implemented. This generator can offer effective and efficient air-gap flux control. First, the characteristics of the proposed generator are analyzed by using the finite element method. Second, the closed-loop flux control is devised to achieve a constant generated voltage under time-varying wind speeds. Finally, the experimental results are given to verify the validity of the proposed generator and control system.

  19. Performance comparison of three-phase flux reversal permanent magnet motors in BLDC and BLAC operation mode

    NASA Astrophysics Data System (ADS)

    Štumberger, B.; Štumberger, G.; Hadžiselimović, M.; Hamler, A.; Goričan, V.; Jesenik, M.; Trlep, M.

    The paper presents a comparison of torque capability and flux-weakening performance of three-phase flux reversal permanent magnet motors with surface and inset permanent magnets. Finite element analysis is employed to determine the performance of each motor in BLDC and BLAC operation mode. It is shown that the torque capability and flux-weakening performance of surface or inset permanent magnet configuration is strongly dependent on the stator teeth number/rotor pole number combination.

  20. Disc formation in turbulent cloud cores: is magnetic flux loss necessary to stop the magnetic braking catastrophe or not?

    NASA Astrophysics Data System (ADS)

    Santos-Lima, R.; de Gouveia Dal Pino, E. M.; Lazarian, A.

    2013-03-01

    Recent numerical analysis of Keplerian disc formation in turbulent, magnetized cloud cores by Santos-Lima et al. demonstrated that reconnection diffusion is an efficient process to remove the magnetic flux excess during the buildup of a rotationally supported disc. This process is induced by fast reconnection of the magnetic fields in a turbulent flow. In a similar numerical study, Seifried et al. concluded that reconnection diffusion or any other non-ideal magnetohydrodynamic effects would not be necessary and turbulence shear alone would provide a natural way to build up a rotating disc without requiring magnetic flux loss. Their conclusion was based on the fact that the mean mass-to-flux ratio (μ) evaluated over a spherical region with a radius much larger than the disc is nearly constant in their models. In this paper, we compare the two sets of simulations and show that this averaging over large scales can mask significant real increases of μ in the inner regions where the disc is built up. We demonstrate that turbulence-induced reconnection diffusion of the magnetic field happens in the initial stages of the disc formation in the turbulent envelope material that is accreting. Our analysis is suggestive that reconnection diffusion is present in both sets of simulations and provides a simple solution for the `magnetic braking catastrophe' which is discussed in the literature in relation to the formation of protostellar accretion discs.

  1. Arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube

    DOEpatents

    Pidcoe, Stephen V.; Zink, Roger A.; Boroski, William N.; McCaw, William R.

    1993-01-01

    An arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube of a magnet such as is used with the Superconducting Super Collider (SSC). The arrangement includes a magnetic field alignment gauge that is carried through the magnet bore tube by a positioning shuttle in predetermined increments. The positioning shuttle includes an extensible body assembly which is actuated by an internal piston arrangement. A pair of spaced inflatable cuffs are carried by the body assembly and are selectively actuated in cooperation with pressurizing of the piston to selectively drive the positioning shuttle in an axial direction. Control of the shuttle is provided by programmed electronic computer means located exteriorly of the bore tube and which controls valves provided pressurized fluid to the inflatable cuss and the piston arrangement.

  2. Evolution of a typical ion-scale magnetic flux rope caused by thermal pressure enhancement

    NASA Astrophysics Data System (ADS)

    Teh, W.-L.; Nakamura, T. K. M.; Nakamura, R.; Baumjohann, W.; Russell, C. T.; Pollock, C.; Lindqvist, P.-A.; Ergun, R. E.; Burch, J. L.; Torbert, R. B.; Giles, B. L.

    2017-02-01

    With high time-resolution field and plasma measurements by the Magnetospheric Multiscale spacecraft, interior fine structures of two ion-scale magnetic flux ropes ( 5 and 11 ion inertial length radius) separated by 14 s are resolved. These two ion-scale flux ropes (FR1 and FR2) show non-frozen-in ion behavior and consist of a strong axial magnetic field at the reversal of the negative-then-positive bipolar field component. The negative bipolar field component of the FR2 is found to be depressed, where magnetic pressure and total pressure decrease, but ion and electron thermal pressures increase, a feature akin to a crater-like flux rope. The pressure enhancement is due to the magnetosheath plasma feeding into the flux rope along the field lines. Magnetic field draping and energetic electrons are also observed in the trailing part of the FR2. The ratio of perpendicular and parallel currents indicates that the FR1 appears force-free but the FR2 seems not. Moreover, the FR2 is time-dependent as a result of a low correlation coefficient (CC = 0.75) for the derivation of the deHoffmann-Teller frame using the direct measured electric fields, while the FR1 is in quasi-steady conditions (CC = 0.94). It is concluded that the crater formation within the FR2 can be interpreted by the analytical flux rope simulation as the evolution of typical flux rope to crater-like one due to the thermal pressure enhancement, which could be induced by the depression of transverse magnetic fields of the flux rope.

  3. Magnetic-field decay of three interlocked flux rings with zero linking number.

    PubMed

    Del Sordo, Fabio; Candelaresi, Simon; Brandenburg, Axel

    2010-03-01

    The resistive decay of chains of three interlocked magnetic flux rings is considered. Depending on the relative orientation of the magnetic field in the three rings, the late-time decay can be either fast or slow. Thus, the qualitative degree of tangledness is less important than the actual value of the linking number or, equivalently, the net magnetic helicity. Our results do not suggest that invariants of higher order than that of the magnetic helicity need to be considered to characterize the decay of the field.

  4. Development of a Permanent-Magnet Microwave Ion Source for a Sealed-Tube Neutron Generator

    SciTech Connect

    Waldmann, Ole; Ludewigt, Bernhard

    2011-03-31

    A microwave ion source has been designed and constructed for use with a sealed-tube, high-yield neutron generator. When operated with a tritium-deuterium gas mixture the generator will be capable of producing 5*1011 n/s in non-proliferation applications. Microwave ion sources are well suited for such a device because they can produce high extracted beam currents with a high atomic fraction at low gas pressures of 0.2-0.3 Pa required for sealed tube operation. The magnetic field strength for achieving electron cyclotron resonance (ECR) condition, 87.5 mT at 2.45 GHz microwave frequency, was generated and shaped with permanent magnets surrounding the plasma chamber and a ferromagnetic plasma electrode. This approach resulted in a compact ion source that matches the neutron generator requirements. The needed proton-equivalent extracted beam current density of 40 mA/cm^2 was obtained at moderate microwave power levels of 400 W. Results on magnetic field design, pressure dependency and atomic fraction measured for different wall materials are presented.

  5. Magnetic Flux Noise in dc SQUIDs: Temperature and Geometry Dependence

    DTIC Science & Technology

    2013-04-05

    with a slope that flattens at higher frequencies as the white noise from the shunt resistors becomes significant. At low frequencies (f & 101 Hz) and...ðfÞ. We performed a least squares fit to SðfÞ ¼ A2=ðf=1 HzÞ þ C2, representing the flux 1=f noise and the white noise from the resistive shunts, to...we made measure- ments at dI=d ¼ 0, enabling us to determine the critical current 1=f noise . We verified that the power spectrum of the white noise

  6. Magnetic Flux Effect on a Kondo-Induced Electric Polarization in a Triangular Triple Quantum Dot

    NASA Astrophysics Data System (ADS)

    Koga, Mikito; Matsumoto, Masashige; Kusunose, Hiroaki

    2014-08-01

    A magnetic flux effect is studied theoretically on an electric polarization induced by the Kondo effect in a triangular triple-quantum-dot system, where one of the three dots is connected to a metallic lead. This electric polarization exhibits an Aharonov-Bohm oscillation as a function of the magnetic flux penetrating through the triangular loop. The numerical renormalization group analysis reveals how the oscillation pattern depends on the Kondo coupling of a local spin with lead electrons, which is sensitive to the point contact with the lead. It provides an experimental implication that the Kondo effect is the origin of the emergent electric polarization.

  7. Multiple Triangulation Analysis: another approach to determine the orientation of magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Zhou, X.-Z.; Zong, Q.-G.; Pu, Z. Y.; Fritz, T. A.; Dunlop, M. W.; Shi, Q. Q.; Wang, J.; Wei, Y.

    2006-07-01

    Another approach (Multiple Triangulation Analysis, MTA) is presented to determine the orientation of magnetic flux rope, based on 4-point measurements. A 2-D flux rope model is used to examine the accuracy of the MTA technique in a theoretical way. It is found that the precision of the estimated orientation is dependent on both the spacecraft separation and the constellation path relative to the flux rope structure. However, the MTA error range can be shown to be smaller than that of the traditional MVA technique. As an application to real Cluster data, several flux rope events on 26 January 2001 are analyzed using MTA, to obtain their orientations. The results are compared with the ones obtained by several other methods which also yield flux rope orientation. The estimated axis orientations are shown to be fairly close, suggesting the reliability of the MTA method.

  8. A TORSIONAL ALFVEN WAVE EMBEDDED WITHIN A SMALL MAGNETIC FLUX ROPE IN THE SOLAR WIND

    SciTech Connect

    Gosling, J. T.; Teh, W.-L.; Eriksson, S.

    2010-08-10

    We describe and use novel techniques to analyze a striking and distinct solar wind event observed by two spacecraft. We show that the event is consistent with an interpretation as a torsional Alfven wave embedded within a small, nearly radially aligned, magnetic flux rope of total width {approx}10{sup 6} km. It seems likely that the torsional wave was generated by distortions produced within a pre-existing flux rope that erupted from the Sun. Our examination of many events previously identified as flux ropes in the solar wind indicates that torsional Alfven waves are extremely rare in such events.

  9. Measurement of the Magnetic Flux Noise Spectrum in Superconducting Xmon Transmon Quantum Bits

    NASA Astrophysics Data System (ADS)

    Chiaro, Ben; Sank, D.; Kelly, J.; Chen, Z.; Campbell, B.; Dunsworth, A.; O'Malley, P.; Neill, C.; Quintana, C.; Vainsencher, A.; Wenner, J.; Barends, R.; Chen, Y.; Fowler, A.; Jeffrey, E.; Migrant, A.; Mutus, J.; Roushan, P.; White, T.; Martinis, J. M.

    Dephasing induced by magnetic flux noise limits the performance of modern superconducting quantum processors. We measure the flux noise power spectrum in planar, frequency-tunable, Xmon transmon quantum bits (qubits), with several SQUID loop geometries. We extend the Ramsey Tomography Oscilloscope (RTO) technique by rapid sampling up to 1 MHz, without state reset, to measure the flux noise power spectrum between 10-2 and 105 Hz. The RTO measurements are combined with idle gate randomized benchmarking and Ramsey decay to give a more complete picture of dephasing in SQUID-based devices.

  10. Evidence in Magnetic Clouds for Systematic Open Flux Transport on the Sun

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    Most magnetic clouds encountered by spacecraft at 1 AU display a mix of unidirectional suprathermal electrons signaling open field lines and counterstreaming electrons signaling loops connected to the Sun at both ends. Assuming the open fields were originally loops that underwent interchange reconnection with open fields at the Sun, we determine the sense of connectedness of the open fields found in 72 of 97 magnetic clouds identified by the Wind spacecraft in order to obtain information on the location and sense of the reconnection and resulting flux transport at the Sun. The true polarity of the open fields in each magnetic cloud was determined from the direction of the suprathermal electron flow relative to the magnetic field direction. Results indicate that the polarity of all open fields within a given magnetic cloud is the same 89% of the time, implying that interchange reconnection at the Sun most often occurs in only one leg of a flux rope loop, thus transporting open flux in a single direction, from a coronal hole near that leg to the foot point of the opposite leg. This pattern is consistent with the view that interchange reconnection in coronal mass ejections systematically transports an amount of open flux sufficient to reverse the polarity of the heliospheric field through the course of the solar cycle. Using the same electron data, we also find that the fields encountered in magnetic clouds are only a third as likely to be locally inverted as not. While one might expect inversions to be equally as common as not in flux rope coils, consideration of the geometry of spacecraft trajectories relative to the modeled magnetic cloud axes leads us to conclude that the result is reasonable.

  11. SOLAR MAGNETIC TRACKING. III. APPARENT UNIPOLAR FLUX EMERGENCE IN HIGH-RESOLUTION OBSERVATIONS

    SciTech Connect

    Lamb, D. A.; DeForest, C. E.; Hagenaar, H. J.; Parnell, C. E.; Welsch, B. T.

    2010-09-10

    Understanding the behavior of weak magnetic fields near the detection limit of current instrumentation is important for determining the flux budget of the solar photosphere at small spatial scales. Using 0.''3-resolution magnetograms from the Solar Optical Telescope's Narrowband Filter Imager (NFI) on the Hinode spacecraft, we confirm that the previously reported apparent unipolar magnetic flux emergence seen in intermediate-resolution magnetograms is indeed the coalescence of previously existing flux. We demonstrate that similar but smaller events seen in NFI magnetograms are also likely to correspond to the coalescence of previously existing weak fields. The uncoalesced flux, detectable only in the ensemble average of hundreds of these events, accounts for 50% of the total flux within 3 Mm of the detected features. The spatial scale at which apparent unipolar emergence can be directly observed as coalescence remains unknown. The polarity of the coalescing flux is more balanced than would be expected given the imbalance of the data set, however without further study we cannot speculate whether this implies that the flux in the apparent unipolar emergence events is produced by a granulation-scale dynamo or is recycled from existing field.

  12. A miniaturized human-motion energy harvester using flux-guided magnet stacks

    NASA Astrophysics Data System (ADS)

    Halim, M. A.; Park, J. Y.

    2016-11-01

    We present a miniaturized electromagnetic energy harvester (EMEH) using two flux-guided magnet stacks to harvest energy from human-generated vibration such as handshaking. Each flux-guided magnet stack increases (40%) the magnetic flux density by guiding the flux lines through a soft magnetic material. The EMEH has been designed to up-convert the applied human-motion vibration to a high-frequency oscillation by mechanical impact of a spring-less structure. The high-frequency oscillator consists of the analyzed 2-magnet stack and a customized helical compression spring. A standard AAA battery sized prototype (3.9 cm3) can generate maximum 203 μW average power from human hand-shaking vibration. It has a maximum average power density of 52 μWcm-3 which is significantly higher than the current state-of-the-art devices. A 6-stage multiplier and rectifier circuit interfaces the harvester with a wearable electronic load (wrist watch) to demonstrate its capability of powering small- scale electronic systems from human-generated vibration.

  13. Reduction of Thermal Loss in HTS Windings by Using Magnetic Flux Deflection

    NASA Astrophysics Data System (ADS)

    Tsuzuki, K.; Miki, M.; Felder, B.; Koshiba, Y.; Izumi, M.; Umemoto, K.; Aizawa, K.; Yanamoto, T.

    Efforts on the generation of intensified magnetic flux have been made for the optimized shape of HTS winding applications. This contributes to the high efficiency of the rotating machines using HTS windings. Heat generation from the HTS windings requires to be suppressed as much as possible, when those coils are under operation with either direct or alternative currents. Presently, the reduction of such thermal loss generated by the applied currents on the HTS coils is reported with a magnetic flux deflection system. The HTS coils are fixed together with flattened magnetic materials to realize a kind of redirection of the flux pathway. Eventually, the magnetic flux density perpendicular to the tape surface (equivalent to the a-b plane) of the HTS tape materials is reduced to the proximity of the HTS coil. To verify the new geometry of the surroundings of the HTS coils with magnetic materials, a comparative study of the DC coil voltage was done for different applied currents in prototype field-pole coils of a ship propulsion motor.

  14. Dynamic analysis of a magnetic bearing system with flux control

    NASA Technical Reports Server (NTRS)

    Knight, Josiah; Walsh, Thomas; Virgin, Lawrence

    1994-01-01

    Using measured values of two-dimensional forces in a magnetic actuator, equations of motion for an active magnetic bearing are presented. The presence of geometric coupling between coordinate directions causes the equations of motion to be nonlinear. Two methods are used to examine the unbalance response of the system: simulation by direct integration in time; and determination of approximate steady state solutions by harmonic balance. For relatively large values of the derivative control coefficient, the system behaves in an essentially linear manner, but for lower values of this parameter, or for higher values of the coupling coefficient, the response shows a split of amplitudes in the two principal directions. This bifurcation is sensitive to initial conditions. The harmonic balance solution shows that the separation of amplitudes actually corresponds to a change in stability of multiple coexisting solutions.

  15. On the Ratio of Periods of the Fundamental Harmonic and First Overtone of Magnetic Tube Kink Oscillations

    NASA Astrophysics Data System (ADS)

    Ruderman, M. S.; Petrukhin, N. S.; Pelinovsky, E.

    2016-04-01

    We study kink oscillations of thin magnetic tubes. We assume that the density inside and outside the tube (and possibly also the cross-section radius) can vary along the tube. This variation is assumed to be of such a form that the kink speed is symmetric with respect to the tube centre and varies monotonically from the tube ends to the tube centre. Then we prove a theorem stating that the ratio of periods of the fundamental mode and first overtone is a monotonically increasing function of the ratio of the kink speed at the tube centre and the tube ends. In particular, it follows from this theorem that the period ratio is lower than two when the kink speed increases from the tube ends to its centre, while it is higher than two when the kink speed decreases from the tube ends to its centre. The first case is typical for non-expanding coronal magnetic loops, and the second for prominence threads. We apply the general results to particular problems. First we consider kink oscillations of coronal magnetic loops. We prove that, under reasonable assumptions, the ratio of the fundamental period to the first overtone is lower than two and decreases when the loop size increases. The second problem concerns kink oscillations of prominence threads. We consider three internal density profiles: generalised parabolic, Gaussian, and Lorentzian. Each of these profiles contain the parameter α that is responsible for its sharpness. We calculate the dependence of the period ratio on the ratio of the mean to the maximum density. For all considered values of α we find that a formula relating the period ratio and the ratio of the mean and maximum density suggested by Soler, Goossens, and Ballester ( Astron. Astrophys. 575, A123, 2015) gives a sufficiently good approximation to the exact dependence.

  16. Geometrical investigation of the kinetic evolution of the magnetic field in a periodic flux rope

    SciTech Connect

    Restante, A. L.; Lapenta, G.; Markidis, S.; Intrator, T.

    2013-08-15

    Flux ropes are bundles of magnetic field wrapped around an axis. Many laboratory, space, and astrophysics processes can be represented using this idealized concept. Here, a massively parallel 3D kinetic simulation of a periodic flux rope undergoing the kink instability is studied. The focus is on the topology of the magnetic field and its geometric structures. The analysis considers various techniques such as Poincaré maps and the quasi-separatrix layer (QSL). These are used to highlight regions with expansion or compression and changes in the connectivity of magnetic field lines and consequently to outline regions where heating and current may be generated due to magnetic reconnection. The present study is, to our knowledge, the first QSL analysis of a fully kinetic 3D particle in cell simulation and focuses the existing QSL method of analysis to periodic systems.

  17. 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

  18. Large-Scale Coronal Heating, Clustering of Coronal Bright Points, and Concentration of Magnetic Flux

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    By combining quiet-region Fe XII coronal images from SOHO/EIT with magnetograms from NSO/Kitt Peak and from SOHO/MDI, we show that on scales larger than a supergranule the population of network coronal bright points and the magnetic flux content of the network are both markedly greater under the bright half of the quiet corona than under the dim half. These results (1) support the view that the heating of the entire corona in quiet regions and coronal holes is driven by fine-scale magnetic activity (microflares, explosive events, spicules) seated low in the magnetic network, and (2) suggest that this large-scale modulation of the magnetic flux and coronal heating is a signature of giant convection cells.

  19. 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.

  20. Sensing magnetic flux density of artificial neurons with a MEMS device.

    PubMed

    Tapia, Jesus A; Herrera-May, Agustin L; García-Ramírez, Pedro J; Martinez-Castillo, Jaime; Figueras, Eduard; Flores, Amira; Manjarrez, Elías

    2011-04-01

    We describe a simple procedure to characterize a magnetic field sensor based on microelectromechanical systems (MEMS) technology, which exploits the Lorentz force principle. This sensor is designed to detect, in future applications, the spiking activity of neurons or muscle cells. This procedure is based on the well-known capability that a magnetic MEMS device can be used to sense a small magnetic flux density. In this work, an electronic neuron (FitzHugh-Nagumo) is used to generate controlled spike-like magnetic fields. We show that the magnetic flux density generated by the hardware of this neuron can be detected with a new MEMS magnetic field sensor. This microdevice has a compact resonant structure (700 × 600 × 5 μm) integrated by an array of silicon beams and p-type piezoresistive sensing elements, which need an easy fabrication process. The proposed microsensor has a resolution of 80 nT, a sensitivity of 1.2 V.T(-1), a resonant frequency of 13.87 kHz, low power consumption (2.05 mW), quality factor of 93 at atmospheric pressure, and requires a simple signal processing circuit. The importance of our study is twofold. First, because the artificial neuron can generate well-controlled magnetic flux density, we suggest it could be used to analyze the resolution and performance of different magnetic field sensors intended for neurobiological applications. Second, the introduced MEMS magnetic field sensor may be used as a prototype to develop new high-resolution biomedical microdevices to sense magnetic fields from cardiac tissue, nerves, spinal cord, or the brain.

  1. Predicting the sun's polar magnetic fields with a surface flux transport model

    SciTech Connect

    Upton, Lisa; Hathaway, David H. E-mail: lar0009@uah.edu

    2014-01-01

    The Sun's polar magnetic fields are directly related to solar cycle variability. The strength of the polar fields at the start (minimum) of a cycle determine the subsequent amplitude of that cycle. In addition, the polar field reversals at cycle maximum alter the propagat