WorldWideScience

Sample records for field aligned currents

  1. The field-aligned currents observed by JIKIKEN

    International Nuclear Information System (INIS)

    Aoyama, I.; Toyama, F.; Takahashi, T.; Sakurai, T.; Tonegawa, Y.

    1979-01-01

    New substorm effects on field-aligned current which belongs to a magnetic shell at L asymptotically equals 6 are found in the records from the fluxgate magnetometer on board the scientific satellite, JIKIKEN. The deviation from base line in the magnetometer data seems to be enhanced associating with the substorm onset. (author)

  2. Correlation between Auroral kilometric radiation and field-aligned currents

    International Nuclear Information System (INIS)

    Green, J.L.; Saflekos, N.A.; Gurnett, D.A.; Potemra, T.A.

    1982-01-01

    Simultaneous observations of field-aligned currents (FAC) and auroral kilometric radiation (AKR) are compared from the polar-orbiting satellites Triad and Hawkeye. The Triad observations were restricted to the evening-to-midnight local time sector (1900 to 0100 hours magnetic local time) in the northern hemisphere. This is the region in which the most intense storms of AKR are believed to originate. The Hawkeye observations were restricted to when the satellite was in the AKR emission cone in the northern hemisphere and at radial distances > or =7R/sub E/ (earth radii) to avoid local propagation cutoff effects. A(R/7R/sub E/) 2 normalization to the power flux measurements of the kilometric radiation from Hawkeye is used to take into account the radial dependence of this radiation and to scale all intensity measurements so that they are independent of Hawkeye's position in the emission cone. Integrated field-aligned current intensities from Triad are determined from the observed transverse magnetic field disturbances. There appears to be a weak correlation between AKR intensity and the integrated current sheet intensity of field-aligned currents. In general, as the intensity of auroral kilometric radiation increases so does the integrated auroral zone current sheet intensity increase. Statistically, the linear correlation coefficient between the log of the AKR power flux and the log of the current sheet intensity is 0.57. During weak AKR bursts ( - 18 W m - 2 Hz - 1 ), Triad always observed weak FAC'S ( - 1 ), and when Triad observed large FAC's (> or =0.6 A m - 1 ), the AKR intensity from Hawkeye was moderately intense (10 - 5 to 10 - 14 W m - 2 Hz - 1 ) to intense (>10 - 14 W m - 2 Hz - 1 ). It is not clear from these preliminary results what the exact role is that auroral zone field-aligned currents play in the generation or amplification of auroral kilometric radiation

  3. Field-aligned currents during northward IMF: Morphology and causes

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Moretto, T.; Rastätter, L.

    2005-01-01

    We present the results of a global MHD simulation of solar wind magnetosphere interaction during northward IMF. In particular, we emphasize the effect of the IMF B y component on the reconnection geometry and the mapping along field lines to the polar ionosphere, through field-aligned currents. We...... find that the existence and geometry of the polar cap is closely connected to the IMF B y component. During strictly northward IMF the simulated magnetosphere can remain essentially closed because the solar wind field lines reconnect in both hemispheres, thereby creating newly reconnected closed...... exist both on open and closed field lines and are created by the shear of the newly reconnected field lines against the mantle field as they are convected tailward by the solar wind. When the IMF rotates from northward toward east, the magnetospheric mapping regions of the NBZ currents likewise rotates...

  4. Field-Aligned Current Response to Solar Indices

    DEFF Research Database (Denmark)

    R. Edwards, Thom; Weimer, D. R.; Tobiska, W. K.

    2017-01-01

    Magnetometer data from three satellite missions have been used to analyze and identify the effects of varying solar radiation on the magnitudes and locations of field-aligned currents in the Earth's upper atmosphere. Data from the CHAMP, Ørsted, and Swarm satellite missions have been bought...... together to provide a database spanning a 15 year period. The extensive time frame has been augmented by data from the ACE satellite, as well as a number of indices of solar radiation. This data set has been sorted by a number of solar wind, interplanetary magnetic field, and solar radiation indices...... to evaluate the effects of variations in four different solar indices on the total current in different regions of the polar cap. While the solar indices do not have major influence on the total current of the polar cap when compared to solar wind and interplanetary magnetic field parameters it does appear...

  5. Field-aligned currents near the magnetosphere boundary

    International Nuclear Information System (INIS)

    Hones, E.W. Jr.

    1984-01-01

    This paper describes present thinking about the structure of magnetospheric boundary layers and their roles in the generation of the field-aligned currents that are observed in the polar regions. A principal effect of the momentum loss by magnetosheath plasma to the magnetosphere boundary regions just within the magnetopause, whether it be by a diffusive process or by magnetic reconnection, is the tailward pulling of the surface flux tubes relative to those deeper below the surface. The dayside region 1 currents at low altitudes flow along field lines in the resulting regions of magnetic shear. The direction of the shear and its magnitude, actually measured in the boundary region, confirm that the polarities and intensities of the dayside region 1 currents can be accounted for by this process. The low latitude boundary layer, formerly thought to be threaded entirely by closed field lines, now appears to contain at least some open field lines, newly reconnected, that are in the process of being swept into the high latitude tail to form the plasma mantle. The open flux tubes of the flux transfer events, thought to be the product of patchy reconnection have a spiral magnetic structure whose helicity is such as to suggest currents having the polarities of the region 1 currents. 13 references

  6. Field-aligned currents near the magnetosphere boundary

    International Nuclear Information System (INIS)

    Hones, E.W. Jr.

    1983-01-01

    This paper reviews present thinking about the structure of magnetospheric boundary layers and their roles in the generation of the field-aligned currents that are observed in the polar regions. A principal effect of the momentum loss by magnetosheath plasma to the magnetosphere boundary regions just within the magnetopause, whether it be by a diffusive process or by magnetic reconnection, is the tailward pulling of surface flux tubes relative to those deeper below the surface. The dayside region 1 currents at low altitudes flow along field lines in the resulting regions of magnetic shear. The direction of the shear and its magnitude, measured in the boundary region, confirm tht the polarities and intensities of the dayside region 1 currents can be accounted for by this process. The low latitude boundary layer, formerly thought to be threaded entirely by closed field lines, now appears to contain at least some open field lines, newly reconnected, that are in the process of being swept into the high latitude tail to form the plasma mantle. The open flux tubes of the flux transfer events, thought to be the product of patchy reconnection have a spiral magnetic structure whose helicity is such as to suggest currents having the polarities of the region 1 currents

  7. Electric fields and field-aligned current generation in the magnetosphere

    International Nuclear Information System (INIS)

    Alexeev, I.I.; Belenkaya, E.S.; Kalegaev, V.V.; Lyutov, Yu.G.

    1993-01-01

    The authors present a calculation of the electric potential, field-aligned currents, and plasma convection caused by the penetration of the solar wind electric field into the magnetosphere. Ohm's law and the continuity equation of ionospheric currents are used. It is shown that the large-scale convection system is reversed in the plasma sheet flanks. In this region the plasma flow is antisunward earthward of the neutral line and sunward tailward of it. The interplanetary magnetic field (IMF) B z dependences on the dimension of the magnetopause open-quotes windowsclose quotes which are intersected by open field lines, on the potential drop across the polar cap, and on the distance to the neutral line are determined. Because of the IMF effect and the effect of seasonal or daily variations of the geomagnetic field which violate its symmetry relative to the equatorial plane, there may arise a potential drop along field lines which causes field-aligned currents. The values and directions of these currents, the field-aligned potential drop, and a self-consistent solution for the potential at the ionosphere level for high field-aligned conductivity have been determined. 41 refs., 7 figs

  8. Field-aligned currents during northward interplanetary magnetic field: Morphology and causes

    DEFF Research Database (Denmark)

    Vennerstrøm, Susanne; Moretto, T.; Rastatter, L.

    2005-01-01

    [1] We present the results of a global MHD simulation of solar wind magnetosphere interaction during northward IMF. In particular, we emphasize the effect of the IMF By component on the reconnection geometry and the mapping along field lines to the polar ionosphere, through field-aligned currents....... We find that the existence and geometry of the polar cap is closely connected to the IMF By component. During strictly northward IMF the simulated magnetosphere can remain essentially closed because the solar wind field lines reconnect in both hemispheres, thereby creating newly reconnected closed...... both on open and closed field lines and are created by the shear of the newly reconnected field lines against the mantle field as they are convected tailward by the solar wind. When the IMF rotates from northward toward east, the magnetospheric mapping regions of the NBZ currents likewise rotates...

  9. Linear Response of Field-Aligned Currents to the Interplanetary Electric Field

    DEFF Research Database (Denmark)

    Weimer, D. R.; R. Edwards, T.; Olsen, Nils

    2017-01-01

    Many studies that have shown that the ionospheric, polar cap electric potentials (PCEP) exhibit a “saturation” behavior in response to the level of the driving by the solar wind. As the magnitude of the interplanetary magnetic field (IMF) and electric field (IEF) increase, the PCEP response...... of the field-aligned currents (FAC) with the solar wind/magnetosphere/ionosphere system has a role. As the FAC are more difficult to measure, their behavior in response to the level of the IEF has not been investigated as thoroughly. In order to resolve the question of whether or not the FAC also exhibit...... saturation, we have processed the magnetic field measurements from the Ørsted, CHAMP, and Swarm missions, spanning more than a decade. As the amount of current in each region needs to be known, a new technique is used to separate and sum the current by region, widely known as R0, R1, and R2. These totals...

  10. The influence of conductivities consistent with field-aligned currents on high-latitude convection patterns

    International Nuclear Information System (INIS)

    Blomberg, L.G.; Marklund, G.T.

    1988-02-01

    The influence on the high-latitude ionospheric convection of conductivities associated with upward field-aligned currents is investigated. Potential patterns are calculated from a given distribution of field-aligned currents and a conductivity model. The resulting patterns are shown to be modified considerably by including a coupling term between the conductivity and the field-aligned current in the conductivity model. The clockwise rotation of the entire potential pattern is reduced when the conductivity enhancement coincides with the regions of upward field-aligned current. Also, the electric field within these regions turns out to be rather insensitive to change in the magnitude of the current. In regions of downward current or when the current-dependent conductivity is excluded there is on the other hand an almost linear relationship between current and electric field. Although the particles producing the conductivity enhancement may not be the same as those carrying the major part of the field-aligned current it is clear from observations that there is a positive correlation between upward current conductivity. Therefore, the simple relationship used in this study is believed to reflect rather well the principal features of the current-conductivity coupling, which is of im- portance to the modelling of ionospheric electrodynamics. (With 26 refs.) (authors)

  11. The evening diffuse radio aurora, field-aligned currents and particle precipitation

    International Nuclear Information System (INIS)

    Unwin, R.S.

    1980-01-01

    The relationship of the afternoon/evening diffuse radio aurora, proton and electron precipitation and field-aligned currents is studied with data from the auroral radar at Slope Point, New Zealand, and the ISIS 2 satellite. It is shown that there is a very close association between the radio aurora and (primarily downward) field-aligned currents, which confirms and extends previous work, but that there is no clear relation with either proton or electron precipitation. (author)

  12. Simultaneous field-aligned currents at Swarm and Cluster satellites

    DEFF Research Database (Denmark)

    Dunlop, M. W.; Yang, J. Y.; Yang, Y. Y.

    2015-01-01

    altitude) orbits using a particular Swarm and Cluster conjunction. The Cluster signatures are interpreted and ordered through joint mapping of the ground/magnetospheric footprints and estimation of the auroral zone boundaries (taken as indication of the boundaries of Region 1 and Region 2 currents). We...... find clear evidence of both small-scale and large-scale FACs and clear matching of the behavior and structure of the large-scale currents at both Cluster and Swarm. The methodology is made possible through the joint operations of Cluster and Swarm, which contain, in the first several months of Swarm...

  13. Relationship between PC index and magnetospheric field-aligned currents measured by Swarm satellites

    DEFF Research Database (Denmark)

    Troshichev, О.; Sormakov, D.; Behlke, R.

    2018-01-01

    Abstract The relationship between the magnetospheric field-aligned currents (FAC) monitored by the Swarm satellites and the magnetic activity PC index (which is a proxy of the solar wind energy incoming into the magnetosphere) is examined. It is shown that current intensities measured in the R1...... between the PC index and the intensity of field-aligned currents in the R1 dawn and dusk layers: increase of FAC intensity in the course of substorm development is accompanied by increasing the PC index values. Correlation between PC and FAC intensities in the R2 dawn and dusk layers is also observed...

  14. A numerical model of ionospheric convection derived from field-aligned currents and the corresponding conductivity

    International Nuclear Information System (INIS)

    Blomberg, L.G.; Marklund, G.T.

    1991-08-01

    A numerical model for the calculation of ionospheric convection patterns from given distributions of field-aligned current and ionospheric conductivity is described. The model includes a coupling between the conductivity and the field-aligned current, so that the conductivity peaks in regions of upward current, as is usually observed by measurements. The model is very flexible in that the input distributions, the field-aligned current and the conductivity, have been parametrized in a convenient way. From the primary model output, namely the ionospheric electrostatic potential (or convection) in the corotating frame, a number of other quantities can be computed. These include; the potential in the inertial frame (the transformation takes into account the non-alignment of the Earths magnetic and geographic axes), the potential in the magnetospheric equatorial plane (projected using either a dipole magnetic field model or the Tsyganenko-Usmanov model, and the assumption of either vanishing parallel electric field or a proportionality between parallel potential and upward field-aligned current), the distribution of ionospheric (horizontal) current, and the Joule heating in the ionosphere. This model has been used together with a new snapshot technique to calculate the high-latitude potential distribution prevailing during a particular event by combining information from global auroral images and local measurements of fields and particles. The model potential variation along the satellite orbit was found to be in excellent agreement with that calculated from the measured electric field. The model has also been used to study some fundamental properties of the electrodynamics of the high-latitude ionosphere. The results of these different applications of the model have been published separately. (au) (39 refs.)

  15. Small-scale field-aligned currents observed by the AKEBONO (EXOS-D) satellite

    International Nuclear Information System (INIS)

    Fukunishi, H.; Oya, H.; Kokubun, S.; Tohyama, F.; Mukai, T.; Fujii, R.

    1991-01-01

    The EXOS-D fluxgate magnetometer data obtained at 3,000-10,000 km altitude have shown that small-scale field-aligned currents always exist in large-scale region 1, region 2, cusp and polar cap current systems. Assuming that these small-scale field-aligned currents have current sheet structure, the width of current sheet is estimated to be 5-20 km at ionospheric altitude. By comparing the magnetometer data with charged particle and high frequency plasma wave data simultaneously obtained from EXOS-D, it is found that small-scale currents have one-to-one correspondence with localized electron precipitation events characterized by flux enhancement over a wide energy range from 10 eV to several keV and broadband electrostatic bursts occasionally extending above local plasma frequencies or electron cyclotron frequencies

  16. Field-aligned currents' scale analysis performed with the Swarm constellation

    DEFF Research Database (Denmark)

    Lühr, Hermann; Park, Jaeheung; Gjerløv, Jesper Wittendorff

    2015-01-01

    We present a statistical study of the temporal- and spatial-scale characteristics of different field-aligned current (FAC) types derived with the Swarm satellite formation. We divide FACs into two classes: small-scale, up to some 10 km, which are carried predominantly by kinetic Alfve´n waves...

  17. Alfven Wave Reflection Model of Field-Aligned Currents at Mercury

    Science.gov (United States)

    Lyatsky, Wladislaw; Khazanov, George V.; Slavin, James

    2010-01-01

    An Alfven Wave Reflection (AWR) model is proposed that provides closure for strong field-aligned currents (FACs) driven by the magnetopause reconnection in the magnetospheres of planets having no significant ionospheric and surface electrical conductance. The model is based on properties of the Alfven waves, generated at high altitudes and reflected from the low-conductivity surface of the planet. When magnetospheric convection is very slow, the incident and reflected Alfven waves propagate along approximately the same path. In this case, the net field-aligned currents will be small. However, as the convection speed increases. the reflected wave is displaced relatively to the incident wave so that the incident and reflected waves no longer compensate each other. In this case, the net field-aligned current may be large despite the lack of significant ionospheric and surface conductivity. Our estimate shows that for typical solar wind conditions at Mercury, the magnitude of Region 1-type FACs in Mercury's magnetosphere may reach hundreds of kilo-Amperes. This AWR model of field-aligned currents may provide a solution to the long-standing problem of the closure of FACs in the Mercury's magnetosphere. c2009 Elsevier Inc. All rights reserved.

  18. On the role of neutral flow in field-aligned currents

    Science.gov (United States)

    Mannucci, Anthony J.; Verkhoglyadova, Olga P.; Meng, Xing; McGranaghan, Ryan

    2018-01-01

    In this brief note we explore the role of the neutral atmosphere in magnetosphere-ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics.

  19. On the role of neutral flow in field-aligned currents

    Directory of Open Access Journals (Sweden)

    A. J. Mannucci

    2018-01-01

    Full Text Available In this brief note we explore the role of the neutral atmosphere in magnetosphere–ionosphere coupling. We analyze momentum balance in the ion rest frame to form hypotheses regarding the role of neutral momentum in the lower ionosphere during geomagnetic storms. Neutral momentum that appears in the ion rest frame is likely the result of momentum imparted to ionospheric ions by solar wind flow and the resultant magnetospheric dynamics. The resulting ion-neutral collisions lead to the existence of an electric field. Horizontal electron flow balances the momentum supplied by this electric field. We suggest a possible role played by the neutral atmosphere in generating field-aligned currents due to local auroral heating. Our physical interpretation suggests that thermospheric neutral dynamics plays a complementary role to the high-latitude field-aligned currents and electric fields resulting from magnetospheric dynamics.

  20. Auroral streamers: characteristics of associated precipitation,convection and field-aligned currents

    Directory of Open Access Journals (Sweden)

    V. A. Sergeev

    2004-01-01

    Full Text Available During the long-duration steady convection activity on 11 December 1998, the development of a few dozen auroral streamers was monitored by Polar UVI instrument in the dark northern nightside ionosphere. On many occasions the DMSP spacecraft crossed the streamer-conjugate regions over the sunlit southern auroral oval, permitting the investigation of the characteristics of ion and electron precipitation, ionospheric convection and field-aligned currents associated with the streamers. We confirm the conjugacy of streamer-associated precipitation, as well as their association with ionospheric plasma streams having a substantial equatorward convection component. The observations display two basic types of streamer-associated precipitation. In its polewardmost half, the streamer-associated (field-aligned accelerated electron precipitation coincides with the strong (≥2–7μA/m2 upward field-aligned currents on the westward flank of the convection stream, sometimes accompanied by enhanced proton precipitation in the adjacent region. In the equatorward portion of the streamer, the enhanced precipitation includes both electrons and protons, often without indication of field-aligned acceleration. Most of these characteristics are consistent with the model describing the generation of the streamer by the narrow plasma bubbles (bursty bulk flows which are contained on dipolarized field lines in the plasma sheet, although the mapping is strongly distorted which makes it difficult to quantitatively interprete the ionospheric image. The convective streams in the ionosphere, when well-resolved, had the maximal convection speeds ∼0.5–1km/s, total field-aligned currents of a few tenths of MA, thicknesses of a few hundreds km and a potential drop of a few kV across the stream. However, this might represent only a small part of the associated flux transport in the equatorial plasma sheet.

    Key words. Ionosphere (electric fiels and

  1. IMF By associated interhemispheric asymmetries in ionospheric convection and field-aligned currents

    Science.gov (United States)

    Kunduri, B.; Baker, J.; Ruohoniemi, J. M.; Clausen, L.; Ribeiro, A.

    2012-12-01

    The solar wind-magnetosphere interaction plays an important role in controlling the dynamics of ionospheric convection. It is widely known that the By component of IMF generates asymmetries in ionospheric convection between the northern and southern polar caps. Some studies show that IMF By-generated electric field penetrates into the closed magnetosphere producing differences in the high latitude ionospheric convection between hemispheres. The differences in convection were attributed to field-aligned potential drop between hemispheres resulting in flow of interhemispheric field aligned currents. In the current paper we present interhemispheric observations of high latitude ionospheric convection on closed field lines in the noon-dusk sector. The observations reveal that the convection is stronger in the northern (southern) hemisphere when IMF By is positive (negative) irrespective of season. The inter-hemispheric differences can be attributed to the flow of interhemispheric field aligned currents which support the existence of oppositely-directed zonal plasma flows in the closed field line regions, suppressing the convection in one hemisphere and aiding it in the other. We estimate the strength of these currents, analyze their characteristics and identify the various factors such as magnetic local time, magnetic latitude and ionospheric conductivity that impact them.

  2. Effects of polar field-aligned currents on the distribution of the electric field and current in the middle and low latitudes ionosphere

    International Nuclear Information System (INIS)

    Maekawa, Koichiro

    1978-01-01

    According to the analysis of the magnetic records from the Triad satellite, it has been found that there are two regions of the field-aligned current of magnetospheric origin along the auroral oval; Region 1 in higher latitude and Region 2 in lower latitude. These currents seem to have important effect on the distribution of electric field and current in the ionosphere, in addition to the Sq electric field and current of ionospheric origin. The global current systems generated by the field-aligned current were calculated, using some simplified ionospheric models. The effect of the field-aligned current on the distribution of electric field and current of the ionosphere at middle and low latitudes was investigated. (Yoshimori, M.)

  3. Field-aligned current density versus electric potential characteristics for magnetospheric flux tubes

    International Nuclear Information System (INIS)

    Lemaire, J.; Scherer, M.

    1983-01-01

    The field-aligned current density (Jsub(tot)) is a non-linear function of the applied potential difference (phi) between the ionosphere and the magnetosphere. This nonlinear function has been calculated for plasma boundary conditions typical in a dayside cusp magnetic flux tube. The J-characteristic of such a flux tube changes when the temperatures of the warm magnetospheric electrons and of the cold ionospheric electrons are modified; it changes also when the relative density of the warm plasma is modified; the presence of trapped secondary electrons changes also the J-characteristic. The partial currents contributed by the warm and cold electrons, and by warm and cold ions are illustrated. The dynamic characteristic of an electric circuit depends on the static characteristic of each component of the sytem: i.e. the resistive ionosphere, the return current region, and the region of particle precipitation whose field-aligned current/voltage characteristics have been studied in this article

  4. A numerical model of ionospheric convection derived from field-aligned current and the corresponding conductivity

    International Nuclear Information System (INIS)

    Blomberg, L.G.; Marklund, G.T.

    1988-03-01

    A numerical model for the calculation of ionospheric convection patterns from given distributions of field-aligned current and ionospheric conductivity is described. The model includes a coupling between the conductivity and the field-aligned current, so that the conductivity peaks in regions of upward current, as usually observed by measurements. The model is very flexible in that the input distributions, the field-aligned current and the conductivity, have been parameterized in a convenient way. From the primary model output, namely the ionospheric electrostatic potential (or convection) in the corotating frame, a number of other quantities can be computed. These include: the potential in a Sun-fixed frame, the distribution of ionospheric (horizontal) current, and the Joule heating in the ionosphere. This model has been used together with input data inferred from satellite measurements to calculate the high-latitude potential distribution prevailing during a particular event. The model potential variation along the satellite orbit was found to be in excellent agreement with the measured electric field. The model has also been used to study some fundamental properties of the electrodynamics of the high-latitude ionosphere. The results of these different applications of the model have been published separately. (With 23 refs.) (authors)

  5. Effect of magnetic field-aligned currents on VLF emissions in the magnetosphere

    International Nuclear Information System (INIS)

    Kulkarni, V.H.

    1988-01-01

    The dispersion relation for the electromagnetic electron cyclotron waves in the presence of magnetic field-aligned currents has been obtained. The kinetic distribution of electrons for the main body of plasma with a temperature anisotropy and a loss cone distribution have been considered. In general, it has been seen that the current moving along the direction of resonant electrons reduce the growth rate. This effect has been analysed in the case of magnetospheric plasma to suggest possible correlations between the Birkeland currents and the emissions of very low frequency (VLF) electromagnetic waves. (author). 19 refs

  6. Relation of field-aligned currents measured by AMPERE project to solar wind and substorms

    Science.gov (United States)

    McPherron, R. L.; Anderson, B. J.; Chu, X.

    2016-12-01

    Magnetic perturbations measured in the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) by the Iridium constellation of spacecraft have been processed to obtain the time history of field-aligned currents (FAC) connecting the magnetosphere to the ionosphere. We find that the strength of these currents is closely related to the strength of the solar wind driver defined as a running average of the previous three hours of the optimum AL (auroral lower) coupling function. The relation is well represented by a saturation model I = A*S*Ss/(S+Ss) with I the current strength in mega Amps, S the driver strength in mV/m, Ss the saturation value of 7.78 mV/m, and A = 2.55 scales the relation to units of current. We also find that in general the upward current on the nightside increases with each substorm expansion onset defined by a combination of the SuperMag SML (SuperMag AL) and midlatitude positive bay (MPB) onset lists. A superposed epoch analysis using 700 onsets in 2010 shows the following: solar wind coupling peaks at expansion onset; dayside outward current starts to increase one hour before onset while nightside outward current starts suddenly at onset; nightside outward current reaches a peak at 28 minutes as do SML and MPB indices; FAC, SML, and MPB respectively take 1, 2, and 3 hours to decay to background. The data indicate that the substorm current wedge is superposed on a pre-existing field-aligned current system and that the location and properties of the current wedge can be studied with the AMPERE data.

  7. Intense auroral field-aligned currents and electrojets detected by rocket-borne fluxgate magnetometer

    International Nuclear Information System (INIS)

    Tohyama, Fumio; Fukunishi, Hiroshi; Takahashi, Takao; Kokubun, Susumu; Fujii, Ryoichi; Yamagishi, Hisao.

    1988-01-01

    The S-310JA-11 and S-310JA-12 rockets, having a vector magnetometer with high sensitivity (1.8 nT) and high sampling frequency (100 Hz), were launched into the aurora on May 29 and July 12, 1985, from Syowa Station, Antarctica. The S-310JA-11 rocket penetrated twice quiet arcs, while the S-310JA-12 rocket traversed across intense and active auroral arcs during a large magnetic substorm. In the S-310JA-12 rocket experiment, intense field-aligned currents of 400 - 600 nT were observed when the rocket penetrated an active arc during the descending flight. The magnetometer on board the S-310JA-12 rocket also detected intense electrojet currents with a center at 110 km on the upward leg and at 108 km on the downward leg. The magnetometer data of the S-310JA-11 rocket showed no distinguished magnetic field variation due to field-aligned current and electrojet. (author)

  8. Field aligned current study during the solar declining- extreme minimum of 23 solar cycle

    Science.gov (United States)

    Nepolian, Jeni Victor; Kumar, Anil; C, Panneerselvam

    Field Aligned Current (FAC) density study has been carried out during the solar declining phase from 2004 to 2006 of the 23rd solar cycle and the ambient terrestrial magnetic field of the extended minimum period of 2008 and 2009. We mainly depended on CHAMP satellite data (http://isdc.gfz-potsdam.de/) for computing the FAC density with backup of IGRF-10 model. The study indicates that, the FAC is controlled by quasi-viscous processes occurring at the flank of the earth’s magnetosphere. The dawn-dusk conventional pattern enhanced during disturbed days. The intensity of R1 current system is higher than the R2 current system. Detailed results will be discussed in the conference.

  9. Theory and observations of upward field-aligned currents at the magnetopause boundary layer.

    Science.gov (United States)

    Wing, Simon; Johnson, Jay R

    2015-11-16

    The dependence of the upward field-aligned current density ( J ‖ ) at the dayside magnetopause boundary layer is well described by a simple analytic model based on a velocity shear generator. A previous observational survey confirmed that the scaling properties predicted by the analytical model are applicable between 11 and 17 MLT. We utilize the analytic model to predict field-aligned currents using solar wind and ionospheric parameters and compare with direct observations. The calculated and observed parallel currents are in excellent agreement, suggesting that the model may be useful to infer boundary layer structures. However, near noon, where velocity shear is small, the kinetic pressure gradients and thermal currents, which are not included in the model, could make a small but significant contribution to J ‖ . Excluding data from noon, our least squares fit returns log( J ‖,max_cal ) = (0.96 ± 0.04) log( J ‖_obs ) + (0.03 ± 0.01) where J ‖,max_cal = calculated J ‖,max and J ‖_obs = observed J ‖ .

  10. Transient, Small-Scale Field-Aligned Currents in the Plasma Sheet Boundary Layer During Storm Time Substorms

    Science.gov (United States)

    Nakamura, R.; Sergeev, V. A.; Baumjohann, W.; Plaschke, F.; Magnes, W.; Fischer, D.; Varsani, A.; Schmid, D.; Nakamura, T. K. M.; Russell, C. T.; hide

    2016-01-01

    We report on field-aligned current observations by the four Magnetospheric Multiscale (MMS) spacecraft near the plasma sheet boundary layer (PSBL) during two major substorms on 23 June 2015. Small-scale field-aligned currents were found embedded in fluctuating PSBL flux tubes near the Separatrix region. We resolve, for the first time, short-lived earthward (downward) intense field-aligned current sheets with thicknesses of a few tens of kilometers, which are well below the ion scale, on flux tubes moving equatorward earth ward during outward plasma sheet expansion. They coincide with upward field-aligned electron beams with energies of a few hundred eV. These electrons are most likely due to acceleration associated with a reconnection jet or high-energy ion beam-produced disturbances. The observations highlight coupling of multiscale processes in PSBL as a consequence of magnetotail reconnection.

  11. Laboratory simulation of the magnetosphere, magnetotail reconnection and the study of field-aligned currents

    International Nuclear Information System (INIS)

    Yur, G.

    1990-01-01

    Laboratory simulation of the Earth's magnetosphere is performed. A wide plasma beam with plasma density ∼ 10 13 cm -3 , velocity ∼ 10 7 cm/s, temperature ∼ 10 eV and pulse duration ∼ 100μs simulates the solar wind plasma. An externally applied magnetic field throughout the interaction chamber is varied between -300 to +300 G to simulate the interplanetary magnet field (IMF). Detailed characterization of the flow of this plasma across the IMF shows various degrees of diamagnetism and rvec E x rvec B propagation. This magnetized plasma beam interacts with a spherical dipole magnetic field that simulates the planetary field to form a planetary type plasma sphere. Cusp structures and particle precipitations are studied with optical time exposure photographs of the simulated magnetosphere. The structure is strongly controlled by the polarity of the IMF. The global structure of the magnetosphere is measured in detail for different values of the IMF at various locations in the magnetosphere. Particularly, the magnetic field measurements in the tail reveal interesting reconnection processes and above the polar region, the structure of field aligned currents that are similar to the ones obtained from the satellites above the polar region of the Earth. The main experimental parameters are selected in such a way that, at least, MHD scaling is satisfied

  12. Estimates of the field-aligned current density in current-carrying filaments using auroral zone ground-based observations

    Directory of Open Access Journals (Sweden)

    M. A. Danielides

    Full Text Available We described the ground signatures of dynamic substorm features as observed by the imaging riometer, magnetometers and all-sky camera (ASC at Kilpisjärvi, Finland on 5 and 25 October 1999 during the late evening hours. The magnetometer data was consistent with the motion of up-ward field-aligned currents (FACs associated with absorption patches moving within the field of view of the riometer. We used riometer data in order to estimate the intensity of FACs associated with these local current-carrying filaments. It is shown that during these events, the estimated FAC intensity exceeds a threshold value that corresponds to the excitation of the low-frequency turbulence in the upper ionosphere. As a result, a quasi-oscillating regime of anomalous resistivity on the auroral field lines can give rise to the burst-like electron acceleration responsible for simultaneously observed auroral forms and bursts of Pi1B pulsations.

    Key words. Ionosphere (active experiments; auroral ionosphere; electric fields and currents

  13. Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

    Directory of Open Access Journals (Sweden)

    D. L. Green

    2009-04-01

    Full Text Available The configuration of the Earth's magnetosphere under various Interplanetary Magnetic Field (IMF and solar wind conditions alters the global distribution of Field-Aligned Currents (FACs at the high latitude ionospheres. We use magnetic field data obtained from the Iridium constellation to extend recent studies that infer the dependence of the global FAC configuration on IMF direction and magnitude, hemisphere and season. New results are a reduced IMF By influence on the FAC configuration for the winter hemisphere and a redistribution of FAC to the nightside for winter relative to the summer hemisphere. These effects are linked to the winter ionosphere conductance distribution being dominated by localised nightside enhancement associated with ionisation from energetic particle precipitation. A comparison of an estimated open-closed field line boundary (OCFLB with the Region 1 FAC locations shows reasonable agreement for summer FAC configurations. However, the OCFLB location is decoupled from the Region 1 FACs in winter, especially for IMF Bz>0.

  14. Seasonal and Temporal Variations of Field-Aligned Currents and Ground Magnetic Deflections During Substorms

    Science.gov (United States)

    Forsyth, C.; Shortt, M.; Coxon, J. C.; Rae, I. J.; Freeman, M. P.; Kalmoni, N. M. E.; Jackman, C. M.; Anderson, B. J.; Milan, S. E.; Burrell, A. G.

    2018-04-01

    Field-aligned currents (FACs), also known as Birkeland currents, are the agents by which energy and momentum are transferred to the ionosphere from the magnetosphere and solar wind. This coupling is enhanced at substorm onset through the formation of the substorm current wedge. Using FAC data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and substorm expansion phase onsets identified using the Substorm Onsets and Phases from Indices of the Electrojet technique, we examine the Northern Hemisphere FACs in all local time sectors with respect to substorm onset and subdivided by season. Our results show that while there is a strong seasonal dependence on the underlying FACs, the increase in FACs following substorm onset only varies by 10% with season, with substorms increasing the hemispheric FACs by 420 kA on average. Over an hour prior to substorm onset, the dayside currents in the postnoon quadrant increase linearly, whereas the nightside currents show a linear increase starting 20-30 min before onset. After onset, the nightside Region 1, Region 2, and nonlocally closed currents and the SuperMAG AL (SML) index follow the Weimer (1994, https://doi.org/10.1029/93JA02721) model with the same time constants in each season. These results contrast earlier contradictory studies that indicate that substorms are either longer in the summer or decay faster in the summer. Our results imply that, on average, substorm FACs do not change with season but that their relative impact on the coupled magnetosphere-ionosphere system does due to the changes in the underlying currents.

  15. The particle carriers of field-aligned currents in the Earth's magnetotail during a substorm

    Science.gov (United States)

    Cheng, Z. W.; Zhang, J. C.; Shi, J. K.; Kistler, L. M.; Dunlop, M.; Dandouras, I.; Fazakerley, A.

    2016-04-01

    Although the particle carriers of field-aligned currents (FACs) in the Earth's magnetotail play an important role in the transfer of momentum and energy between the solar wind, magnetosphere, and ionosphere, the characteristics of the FAC carriers have been poorly understood. Taking advantage of multiinstrument magnetic field and plasma data collected by the four spacecraft of the Cluster constellation as they traversed the northern plasma sheet boundary layer in the magnetotail on 14 September 2004, we identified the species type and energy range of the FAC carriers for the first time. The results indicate that part of tailward FACs is carried by energetic keV ions, which are probably originated from the ionosphere through outflow, and they are not too small (~2 nA/m2) to be ignored. The earthward (tailward) FACs are mainly carried by the dominant tailward (earthward) motion of electrons, and higher-energy electrons (from ~0.5 to 26 keV) are the main carriers.

  16. A Comprehensive Analysis of Multiscale Field-Aligned Currents: Characteristics, Controlling Parameters, and Relationships

    Science.gov (United States)

    McGranaghan, Ryan M.; Mannucci, Anthony J.; Forsyth, Colin

    2017-12-01

    We explore the characteristics, controlling parameters, and relationships of multiscale field-aligned currents (FACs) using a rigorous, comprehensive, and cross-platform analysis. Our unique approach combines FAC data from the Swarm satellites and the Advanced Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to create a database of small-scale (˜10-150 km, 250 km) FACs. We examine these data for the repeatable behavior of FACs across scales (i.e., the characteristics), the dependence on the interplanetary magnetic field orientation, and the degree to which each scale "departs" from nominal large-scale specification. We retrieve new information by utilizing magnetic latitude and local time dependence, correlation analyses, and quantification of the departure of smaller from larger scales. We find that (1) FACs characteristics and dependence on controlling parameters do not map between scales in a straight forward manner, (2) relationships between FAC scales exhibit local time dependence, and (3) the dayside high-latitude region is characterized by remarkably distinct FAC behavior when analyzed at different scales, and the locations of distinction correspond to "anomalous" ionosphere-thermosphere behavior. Comparing with nominal large-scale FACs, we find that differences are characterized by a horseshoe shape, maximizing across dayside local times, and that difference magnitudes increase when smaller-scale observed FACs are considered. We suggest that both new physics and increased resolution of models are required to address the multiscale complexities. We include a summary table of our findings to provide a quick reference for differences between multiscale FACs.

  17. Convection and field-aligned currents, related to polar cap arcs, during strongly northward IMF (11 January 1983)

    International Nuclear Information System (INIS)

    Israelevich, P.L.; Podgorny, I.M.; Kuzmin, A.K.; Nikolaeva, N.S.; Dubinin, E.M.

    1988-01-01

    Electric and magnetic fields and auroral emissions have been measured by the Intercosmos-Bulgaria-1300 satellite on 10-11 January 1983. The measured distributions of the plasma drift velocity show that viscous convection is diminished in the evening sector under IMF B y y > 0. A number of sun-aligned polar cap arcs were observed at the beginning of the period of strongly northward IMF and after a few hours a θ-aurora appeared. The intensity of ionized oxygen emission increased significantly reaching up to several kilo-Rayleighs in the polar cap arc. A complicated pattern of convection and field-aligned currents existed in the nightside polar cap which differed from the four-cell model of convection and NBZ field-aligned current system. This pattern was observed during 12 h and could be interpreted as six large scale field-aligned current sheets and three convective vortices inside the polar cap. Sun-aligned polar cap arcs may be located in regions both of sunward and anti-sunward convection. Structures of smaller spatial scale-correspond to the boundaries of hot plasma regions related to polar cap arcs. Obviously these structures are due to S-shaped distributions of electric potential. Parallel electric fields in these S-structures provide electron acceleration up to 1 keV at the boundaries of polar cap arcs. The pairs of field-aligned currents correspond to those S-structures: a downward current at the external side of the boundary and an upward current at the internal side of it. (author)

  18. Field-aligned current signatures during the March 13-14, 1989, great magnetic storm

    International Nuclear Information System (INIS)

    Fujii, R.; Fukunishi, H.; Kokubun, S.; Sugiura, M.; Tohyama, F.; Hayakawa, H.; Tsuruda, K.; Okada, T.

    1992-01-01

    Characteristics of field-aligned currents (FACs) in the evening and morning regions during the March 13-14, 1989, great magnetic storm have been determined using magnetic and electric field data obtained from the EXOS D spacecraft. This storm began with an SSC at 0128 UT on March 13, and the second SSC occurred at 0747 UT on the same day. The storm continued until March 14. The equatorward boundary of the FAC region began to move equatorward right after the first SSC in both the evening and morning sectors, but the poleward boundary did not immediately respond to the SSC. The equatorward boundary of the FAC system reached as low as below 48 degree invariant latitude, which corresponds to L = 2.2, and the latitudinal width of the FAC region increased greatly, particularly in the morning sector (∼33 degree in invariant latitude). In the evening sector the conventional current system characterized by a pair of upward region 1 and downward region 2 FACs changed into complicated patterns consisting of many pairs of upward and downward FACs with the development of the storm, particularly around 22 UT on March 13 when an intense eastward electrojet was observed as low as 50 degree invariant latitude on the ground. In the morning sector an additional large-scale upward FAC was observed poleward of the conventional downward region 1 and upward region 2 FAC system throughout the storm. In addition, a pair of FACs with a narrow latitudinal width (∼1.5 degree) was observed at the poleward boundary of the extra upward FAC

  19. Energy Flow Exciting Field-Aligned Current at Substorm Expansion Onset

    Science.gov (United States)

    Ebihara, Y.; Tanaka, T.

    2017-12-01

    At substorm expansion onset, upward field-aligned currents (FACs) increase abruptly, and a large amount of electromagnetic energy starts to consume in the polar ionosphere. A question arises as to where the energy comes from. Based on the results obtained by the global magnetohydrodynamics simulation, we present energy flow and energy conversion associated with the upward FACs that manifest the onset. Our simulations show that the cusp/mantle region transmits electromagnetic energy to almost the entire region of the magnetosphere when the interplanetary magnetic field is southward. Integral curve of the Poynting flux shows a spiral moving toward the ionosphere, probably suggesting the pathway of electromagnetic energy from the cusp/mantle dynamo to the ionosphere. The near-Earth reconnection initiates three-dimensional redistribution of the magnetosphere. Flow shear in the near-Earth region results in the generation of the near-Earth dynamo and the onset FACs. The onset FACs are responsible to transport the electromagnetic energy toward the Earth. In the near-Earth region, the electromagnetic energy coming from the cusp/mantle dynamo is converted to the kinetic energy (known as bursty bulk flow) and the thermal energy (associated with high-pressure region in the inner magnetosphere). Then, they are converted to the electromagnetic energy associated with the onset FACs. A part of electromagnetic energy is stored in the lobe region during the growth phase. The release of the stored energy, together with the continuously supplied energy from the cusp/mantle dynamo, contributes to the energy supply to the ionosphere during the expansion phase.

  20. Field-aligned currents observed by CHAMP during the intense 2003 geomagnetic storm events

    Directory of Open Access Journals (Sweden)

    H. Wang

    2006-03-01

    Full Text Available This study concentrates on the characteristics of field-aligned currents (FACs in both hemispheres during the extreme storms in October and November 2003. High-resolution CHAMP magnetic data reflect the dynamics of FACs during these geomagnetic storms, which are different from normal periods. The peak intensity and most equatorward location of FACs in response to the storm phases are examined separately for both hemispheres, as well as for the dayside and nightside. The corresponding large-scale FAC peak densities are, on average, enhanced by about a factor of 5 compared to the quiet-time FACs' strengths. And the FAC densities on the dayside are, on average, 2.5 times larger in the Southern (summer than in the Northern (winter Hemisphere, while the observed intensities on the nightside are comparable between the two hemispheres. Solar wind dynamic pressure is correlated with the FACs strength on the dayside. However, the latitudinal variations of the FACs are compared with the variations in Dst and the interplanetary magnetic field component Bz, in order to determine how these parameters control the large-scale FACs' configuration in the polar region. We have determined that (1 the equatorward shift of FACs on the dayside is directly controlled by the southward IMF Bz and there is a saturation of the latitudinal displacement for large value of negative Bz. In the winter hemisphere this saturation occurs at higher latitudes than in the summer hemisphere. (2 The equatorward expansion of the nightside FACs is delayed with respect to the solar wind input. The poleward recovery of FACs on the nightside is slower than on the dayside. The latitudinal variations on the nightside are better described by the variations of the Dst index. (3 The latitudinal width of the FAC region on the nightside spreads over a wide range of about 25° in latitude.

  1. Laboratory investigation of physical mechanisms of auroral charged particle acceleration in the field-aligned currents layers

    Science.gov (United States)

    Gavrilov, B.; Zetzer, J.; Sobyanin, D.; Podgorny, I.

    One of the major topics of space weather research is to understand auroral structure and the processes that guide, accelerate, and otherwise control particle precipitation and produce auroral substorms. Navigation, communications and radars in the high latitude regions are severely affected through the effects on the ionosphere. It has long been recognized that the direct cause of the aurora is the precipitation of energetic electrons and ions into the atmosphere leading to excitation of the ambient atmospheric gases. Observations of the ionospheric ionization profiles and auroral precipitation characteristics have shown that field-aligned potential drops are formed to create this effect. The problem is that it is not clear the structure of the regions of magnetic field-aligned electric fields and how they are supported in the magnetospheric plasma. The objective of this research is to study the physical mechanisms of these phenomena in a laboratory experiment. It should be achieved by simulating the charged particle acceleration due to field-aligned electrical field generation in all totality of the interconnected events: generation of a plasma flow, its evolution in the magnetic field, polarization of plasma, generation of the field-aligned currents, development of instabilities in the plasma and current layers, double layers or anomalous resistance regions appearance, electrons acceleration. Parameters of the laboratory simulation and preliminary results of the experiment are discussed.

  2. A comparison of field-aligned current signatures simultaneously observed by the MAGSAT and TIROS/NOAA spacecraft

    International Nuclear Information System (INIS)

    Kamide, Y.; Evans, D.S.; Cain, J.C.

    1984-01-01

    In order to examine the relative locations of auroral particle fluxes and field-aligned currents and to identify the main charge carriers of the field-aligned currents at auroral latitudes, nearly simultaneous data from the vector magnetometers on MAGSAT and of precipitating electrons with energies between 300 eV and 20 keV observed by TIROS-N and NOAA-6 are compared. For more than fifty cases, MAGSAT and TIROS and/or NOAA orbits occurred within two minutes (mostly within one minute) of each other in the dawn/dusk sectors, during the time the IMS meridian chains of ground magnetometers were operating from November, 1979 through January, 1980. The latitudinal boundaries of precipitating electrons are found to line up within 1 0 with those of the field-aligned current region. Major portions of the upward field-aligned currents in the poleward half of the evening-sector auroral oval and in the equatorward half of the morining-sector auroral oval appear to be carried by the precipitating keV electrons. (author)

  3. Shape, size, velocity and field-aligned currents of dayside plasma injections: a multi-altitude study

    Directory of Open Access Journals (Sweden)

    A. Marchaudon

    2009-03-01

    Full Text Available On 20 February 2005, Cluster in the outer magnetosphere and Double Star-2 (TC-2 at mid-altitude are situated in the vicinity of the northern cusp/mantle, with Cluster moving sunward and TC-2 anti-sunward. Their magnetic footprints come very close together at about 15:28 UT, over the common field-of-view of SuperDARN radars. Thanks to this conjunction, we determine the velocity, the transverse sizes, perpendicular and parallel to this velocity, and the shape of three magnetic flux tubes of magnetosheath plasma injection. The velocity of the structures determined from the Cluster four-spacecraft timing analysis is almost purely antisunward, in contrast with the antisunward and duskward convection velocity inside the flux tubes. The transverse sizes are defined from the Cluster-TC-2 separation perpendicular to the magnetic field, and from the time spent by a Cluster spacecraft in one structure; they are comprised between 0.6 and 2 RE in agreement with previous studies. Finally, using a comparison between the eigenvectors deduced from a variance analysis of the magnetic perturbation at the four Cluster and at TC-2, we show that the upstream side of the injection flux tubes is magnetically well defined, with even a concave front for the third one giving a bean-like shape, whereas the downstream side is far more turbulent. We also realise the first quantitative comparison between field-aligned currents at Cluster calculated with the curlometer technique and with the single-spacecraft method, assuming infinite parallel current sheets and taking into account the velocity of the injection flux tubes. The results agree nicely, confirming the validity of both methods. Finally, we compare the field-aligned current distribution of the three injection flux tubes at the altitudes of Cluster and TC-2. Both profiles are fairly similar, with mainly a pair of opposite field-aligned currents, upward at low-latitude and downward at high-latitude. In terms of

  4. Three-dimensional equilibria for the extended magnetotail and the generation of field-aligned current sheets

    International Nuclear Information System (INIS)

    Birn, J.

    1989-01-01

    Using the magnetotail equilibrium theory and a solution method outlined by Birn (1987), we have constructed self-consistent three-dimensional models for the quiet average magnetotail beyond about 20 R/sub E/ distance but earthward of a potential distant neutral line, which take into account the decrease of the tail flaring with distance. We find that this effect is coupled with the presence of magnetic shear and thus with field-aligned electric currents. These currents have the signature of region 1 currents, toward the Earth on the dawnside and away on the duskside, and contribute about 5 x 10 5 A to the total Birkeland current. They are strongly concentrated near the plasma sheet-lobe boundary and increase toward the flanks of the tail. Associated with the field-aligned currents and the corresponding magnetic field shear there is a bulging effect that tends to deform a circular cross section of the tail near the Earth into one that has bulges in the low-latitude boundary region. We argue that this effect may be the cause for increased interaction with the solar wind in these regions, producing interconnected fields and tailward flowing plasma on magnetospheric-like fields in the low-latitude boundary layer, and deforming this boundary region into the observed dog bone shape of the plasma sheet cross section. copyright American Geophysical Union 1989

  5. Space Technology 5 (ST-5) Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents

    Science.gov (United States)

    Le, Guan

    2010-01-01

    Space Technology 5 (ST-5) is a three micro-satellite constellation deployed into a 300 x 4500 km, dawn-dusk, sun-synchronous polar orbit from March 22 to June 21, 2006, for technology validations. In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total RI currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of approx. 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  6. Rocket measurement of auroral electron fluxes associated with field-aligned currents

    International Nuclear Information System (INIS)

    Pazich, P.M.; Anderson, H.R.

    1975-01-01

    A Nike-Tomahawk rocket was instrumented with a vector magnetometer and an array of particle detectors including an electron and proton energyspectrometer covering the energy range 0.5-20 keV in seven fixed intervals and measuring the pitch angle distribution from 0degree to 180degree as the rocket spun. The payload was launched from Poker Flat, Alaska, at 0722 UT on February 25, 1972, over a bright auroral band that evidently was the poleward electron aurora, beyond the trapping boundary. An upper limit to the measured proton flux was 10 6 /cm 2 s sr keV. The energy spectrum of the electron flux measured during passage over the visible aurora always exhibited a peak within the measured energy range. During passage over the brighter auroral forms the peak shifted from approx.3 to approx.10 keV, the pitch angle distribution became peaked along B, and the intensity increased. Maximum fluxes of approx.3times10 8 el/cm 2 s sr keV were seen over the aurora, which reached approx.60 kR of lambda5577. The electron flux in regions of maximum flux tended to be the most field-aligned in the energy interval showing the highest intensity

  7. Identifications of the polar cap boundary and the auroral belt in the high-altitude magnetosphere: a model for field-aligned currents

    International Nuclear Information System (INIS)

    Sugiura, M.

    1975-01-01

    By means of the Ogo 5 Goddard Space Flight Center fluxgate magnetometer data the polar cap boundary is identified in the high-altitude magnetosphere by a sudden transition from a dipolar field to a more taillike configuration. It is inferred that there exists a field-aligned-current layer at the polar cap boundary. In the night side magnetosphere the polar cap boundary is identified as the high-latitude boundary of the plasma sheet. The field-aligned current flows downward to the ionosphere on the morning side of the magnetosphere and upward from the ionosphere on the afternoon side. The basic pattern of the magnetic field variations observed during the satellite's traversal of the auroral belt is presented. Currents flow in opposite directions in the two field-aligned-current layers. The current directions in these layers as observed by Ogo 5 in the high-altitude magnetosphere are the same as those observed at low altitudes by the polar-orbiting Triad satellite (Armstrong and Zmuda, 1973). The magnetic field in the region where the lower-latitude field-aligned-current layer is situated is essentially meridional. A model is presented in which two field-aligned-current systems, one at the polar cap boundary and the other on the low-latitude part of the auroral belt, are main []y connected by ionospheric currents flowing across the auroral belt. The existence of field-aligned currents deduced from the Ogo 5 observations is a permanent feature of the magnetosphere. Intensifications of the field-aligned currents and occurrences of multiple pairs of field-aligned-current layers characterize the disturbed conditions of these regions

  8. Magnetosphere-ionosphere coupling currents in Jupiter's middle magnetosphere: effect of magnetosphere-ionosphere decoupling by field-aligned auroral voltages

    Directory of Open Access Journals (Sweden)

    J. D. Nichols

    2005-03-01

    Full Text Available We consider the effect of field-aligned voltages on the magnetosphere-ionosphere coupling current system associated with the breakdown of rigid corotation of equatorial plasma in Jupiter's middle magnetosphere. Previous analyses have assumed perfect mapping of the electric field and flow along equipotential field lines between the equatorial plane and the ionosphere, whereas it has been shown that substantial field-aligned voltages must exist to drive the field-aligned currents associated with the main auroral oval. The effect of these field-aligned voltages is to decouple the flow of the equatorial and ionospheric plasma, such that their angular velocities are in general different from each other. In this paper we self-consistently include the field-aligned voltages in computing the plasma flows and currents in the system. A third order differential equation is derived for the ionospheric plasma angular velocity, and a power series solution obtained which reduces to previous solutions in the limit that the field-aligned voltage is small. Results are obtained to second order in the power series, and are compared to the original zeroth order results with no parallel voltage. We find that for system parameters appropriate to Jupiter the effect of the field-aligned voltages on the solutions is small, thus validating the results of previously-published analyses.

  9. ST5 Observations of the Imbalance of Region 1 and 2 Field-Aligned Currents and Its Implication to the Cross-Polar Cap Pedersen Currents

    Science.gov (United States)

    Le, Guan; Slavin, J. A.; Strangeway, Robert

    2011-01-01

    In this study, we use the in-situ magnetic field observations from Space Technology 5 mission to quantify the imbalance of Region 1 (R1) and Region 2 (R2) currents. During the three-month duration of the ST5 mission, geomagnetic conditions range from quiet to moderately active. We find that the R1 current intensity is consistently stronger than the R2 current intensity both for the dawnside and the duskside large-scale field-aligned current system. The net currents flowing into (out of) the ionosphere in the dawnside (duskside) are in the order of 5% of the total R1 currents. We also find that the net currents flowing into or out of the ionosphere are controlled by the solar wind-magnetosphere interaction in the same way as the field-aligned currents themselves are. Since the net currents due to the imbalance of the R1 and R2 currents require that their closure currents flow across the polar cap from dawn to dusk as Pedersen currents, our results indicate that the total amount of the cross-polar cap Pedersen currents is in the order of 0.1 MA. This study, although with a very limited dataset, is one of the first attempts to quantify the cross-polar cap Pedersen currents. Given the importance of the Joule heating due to Pedersen currents to the high-latitude ionospheric electrodynamics, quantifying the cross-polar cap Pedersen currents and associated Joule heating is needed for developing models of the magnetosphere-ionosphere coupling.

  10. Field-aligned currents and convection patterns in the Southern Polar Cap during stable northward, southward, and azimuthal IMF

    International Nuclear Information System (INIS)

    Papitashvili, V.O.; Belov, B.A.; Gromova, L.I.

    1989-01-01

    Equivalent ionospheric current patterns are derived from ground-based geomagnetic observations for events on 11-12 November 1979 (B/sub z/ >> 0), 24 November 1981 (B/sub z/ > 0) (B/sub y/ >> 0), and 25-26 November 1979 (B/sub y/ 0 . Due to stable external conditions, it is possible to calculate the field-aligned current (FAC) density within cells formed by two adjacent stations by taking into account the uniform conductivity of the summer polar ionosphere. These results completely correspond to regressional analysis of interplanetary magnetic fields (IMF) and ground-based geomagnetic data, and also to satellite observations of the NBZ current system. During stable southward IMF a new result was obtained, a reversal of antisunward convection flow is identified, and an NBZ-like FAC system is restored in the central part of the southern polar cap. The authors conclude that there may be an additional NBZ-like FAC system poleward of -85 0 , which is independent of the IMF and is generated by the quasi-viscous interaction between solar-wind plasma and high-latitude lobes of the magnetospheric tail

  11. Three-dimensional MHD simulation of the interaction of the solar wind with the earth's magnetosphere: The generation of field-aligned currents

    International Nuclear Information System (INIS)

    Ogino, T.

    1986-01-01

    A global computer simulation of the interaction of the solar wind with the earth's magnetosphere was executed by using a three-dimensional magnetohydrodynamic model. As a result, we were able to reproduce quasi-steady-state magnetospheric configurations and a Birkeland field-aligned current system which depend on the polarity of the z component of the interplanetary magnetic field (IMF). Twin convection cells and a dawn to dusk electric potential of 30--100 kV appeared at the equator in the magnetosphere. Four types of field-aligned currents were observed. Region 1 and 2 field-aligned currents generated for all IMF conditions were 0.6--1.0 x 10 6 A and 0.15--0.61 x 10 6 A, respectively, in the total current. Region 1 currents at high latitudes are generated from the field-aligned vorticity at the flanks through a viscous interaction and are strengthened by a twisting of open magnetic field lines in the tail region for southward IMF. On the other hand, the low-latitude region 2 currents probably are generated mainly from the inner pressure gradient of the plasma sheet. The region 1 current obtained from the simulation was in good agreement with an estimate from our theoretical analysis of the localized Alfven mode. The other two types of field-aligned currents are the dayside magnetopause currents in the dayside cusp region, which increase for northward IMF, and the dayside cusp currents for southward IMF. The cusp currents are associated with a twisting of open magnetic field lines in the magnetopause region

  12. Field-aligned currents and ionospheric parameters deduced from EISCAT radar measurements in the post-midnight sector

    Directory of Open Access Journals (Sweden)

    M. Sugino

    2002-09-01

    Full Text Available Attempting to derive the field-aligned current (FAC density using the EISCAT radar and to understand the role of the ionosphere on closing FACs, we conducted special radar experiments with the EISCAT radar on 9 October 1999. In order to derive the gradient of the ionospheric conductivity (grad S and the divergence of the electric field (div E nearly simultaneously, a special experiment employed an EISCAT radar mode which let the transmitting antenna sequentially point to four directions within 10 min; two pairs of the four directions formed two orthogonal diagonals of a square.  Our analysis of the EISCAT radar data disclosed that SP div E and E · grad SP produced FACs with the same direction inside a stable broad arc around 05:00 MLT, when the EISCAT radar presumably crossed the boundary between the large-scale upward and downward current regions. In the most successfully observed case, in which the conductances and the electric field were spatially varying with little temporal variations, the contribution of SP div E was nearly twice as large as that of E · grad SP . On the other hand, the contribution of (b × E · grad SH was small and not effective in closing FACs. The present EISCAT radar mode along with auroral images also enables us to focus on the temporal or spatial variation of high electric fields associated with auroral arcs. In the present experiment, the electric field associated with a stable arc was confined in a spatially restricted region, within ~ 100 km from the arc, with no distinct depletion of electron density. We also detected a region of the high arc-associated electric field, accompanied by the depletion of electron density above 110 km. Using auroral images, this region was identified as a dark spot with a spatial scale of over 150 × 150 km. The dark spot and the electron depletion were likely in existence for a limited time of a few minutes.Key words. Ionosphere (auroral ionosphere; electric fields and currents

  13. Correlations between Geomagnetic Disturbances and Field-Aligned Currents during the 22-29 July 2004 Storm Time Interval

    Science.gov (United States)

    Hood, R.; Woodroffe, J. R.; Morley, S.; Aruliah, A. L.

    2017-12-01

    Using the CHAMP fluxgate magnetometer to calculate field-aligned current (FAC) densities and magnetic latitudes, with SuperMAG ground magnetometers analogously providing ground geomagnetic disturbances (GMD) magnetic perturbations and latitudes, we probe FAC locations and strengths as predictors of GMD locations and strengths. We also study the relationships between solar wind drivers and global magnetospheric activity, and both FACs and GMDs using IMF Bz and the Sym-H index. We present an event study of the 22-29 July 2004 storm time interval, which had particularly large GMDs given its storm intensity. We find no correlation between FAC and GMD magnitudes, perhaps due to CHAMP orbit limitations or ground magnetometer coverage. There is, however, a correlation between IMF Bz and nightside GMD magnitudes, supportive of their generation via tail reconnection. IMF Bz is also correlated with dayside FAC and GMD magnetic latitudes, indicating solar wind as an initial driver. The ring current influence increases during the final storm, with improved correlations between the Sym-H index and both FAC magnetic latitudes and GMD magnitudes. Sym-H index correlations may only be valid for higher intensity storms; a statistical analysis of many storms is needed to verify this.

  14. Field-aligned current signatures in the near-tail region. 2. Coupling between the region 1 and region 2 systems

    International Nuclear Information System (INIS)

    Ohtani, S.; Kokubun, S.; Nakamura, R.; Elphic, R.C.; Russell, C.T.; Baker, D.N.

    1990-01-01

    The development of the substorm-associated current system in the near-tail region is examined in the light of both experiment and theory. First, the March 28, 1979, event is examined intensively by using ground magnetometer data and satellite magnetic field and energetic particle data. The comparison of field-aligned current signatures at geosynchronous altitude and in the near-tail region indicates that the development of the region 1 system is not merely the enhancement in current intensity of the pre-existing system. This finding is consistent with the so-called current wedge model, in which the tail current is converted into a pair of field-aligned currents with the region 1 polarity at substorm onsets. Detailed inspection, however, suggests that the region 2 system is as important as the region 1 system. Statistical properties of the azimuthal magnetic component at synchronous orbit indicate that the deviation during disturbed periods is larger than expected from the enhancement of the region 1 current. These individual and statistical studies suggest that the region 2 system tends to develop in the synchronous region and that the coupling between the region 1 and the region 2 systems is important. The current closure in the magnetosphere is discussed from a viewpoint of the macroscopic behavior of plasma. It is suggested that the dawnside and the duskside region 2 currents are closed in the magnetosphere by the curvature current during the growth phase and by the magnetic gradient current during the expansion phase. The field-aligned currents of the region 1 and the region 2 systems are closed in the ionosphere by the Pedersen current. Consequently, the energy is dissipated as the Joule heating and this energy must be supplied from the magnetosphere. Therefore, the counter part of the Pedersen current, which closes the region 1 and the region 2 currents in magnetosphere, must be the dynamo current

  15. An investigation of the field-aligned currents associated with a large-scale ULF wave using data from CUTLASS and FAST

    Directory of Open Access Journals (Sweden)

    H. C. Scoffield

    2005-02-01

    Full Text Available On 14 December 1999, a large-scale ULF wave event was observed by the Hankasalmi radar of the SuperDARN chain. Simultaneously, the FAST satellite passed through the Hankasalmi field-of-view, measuring the magnetic field oscillations of the wave at around 2000km altitude, along with the precipitating ion and electron populations associated with these fields. A simple field line resonance model of the wave has been created and scaled using the wave's spatial and temporal characteristics inferred from SuperDARN and IMAGE magnetometer data. Here the model calculated field-aligned current is compared with field-aligned currents derived from the FAST energetic particle spectra and magnetic field measurements. This comparison reveals the small-scale structuring and energies of the current carriers in a large-scale Alfvén wave, a topic, which at present, is of considerable theoretical interest. When FAST traverses a region of the wave involving low upward field-aligned current densities, the current appears to be carried by unstructured downgoing electrons of energies less than 30eV. A downward current region appears to be carried partially by upgoing electrons below the FAST energy detection threshold, but also consists of a mixture of hotter downgoing magnetospheric electrons and upgoing ionospheric electrons of energies <30eV, with the hotter upgoing electrons presumably representing those upgoing electrons which have been accelerated by the wave field above the low energy detection threshold of FAST. A stronger interval of upward current shows that small-scale structuring of scale ~50km has been imposed on the current carriers, which are downgoing magnetospheric electrons of energy 0-500eV.

  16. Studies of Westward Electrojets and Field-Aligned Currents in the Magnetotail During Substorms: Implications for Magnetic Field Models

    Science.gov (United States)

    Spence, Harlan E.

    1996-01-01

    This section outlines those tasks undertaken in the final year that contribute integrally to the overarching project goals. Fast, during the final year, it is important to note that the project benefited greatly with the addition of a Boston University graduate student, Ms. Karen Hirsch. Jointly, we made substantial progress on the development of and improvements to magnetotail magnetic field and plasma models. The ultimate aim of this specific task was to assess critically the utility of such models for mapping low-altitude phenomena into the magnetotail (and vice-versa). The bulk of this effort centered around the finite-width- magnetotail convection model developed by and described by Spence and Kivelson (J. Geophys. Res., 98, 15,487, 1993). This analytic, theoretical model specifies the bulk plasma characteristics of the magnetotail plasma sheet (number density, temperature, pressure) across the full width of the tail from the inner edge of the plasma sheet to lunar distances. Model outputs are specified by boundary conditions of the source particle populations as well as the magnetic and electric field configuration. During the reporting period, we modified this code such that it can be interfaced with the auroral particle precipitation model developed by Dr. Terry Onsager. Together, our models provide a simple analytic specification of the equatorial distribution of fields and plasma along with their low-altitude consequences. Specifically, we have built a simple, yet powerful tool which allows us to indirectly 'map' auroral precipitation signatures (VDIS, inverted-V's, etc.) measured by polar orbiting spacecraft in the ionosphere, to the magnetospheric equatorial plane. The combined models allow us to associate latitudinal gradients measured in the ion energy fluxes at low-altitudes with the large-scale pressure gradients in the equatorial plane. Given this global, quasi-static association, we can then make fairly strong statements regarding the location of

  17. Tracing magnetic fields with aligned grains

    International Nuclear Information System (INIS)

    Lazarian, A.

    2007-01-01

    Magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g., transport of heat), and cosmic rays. One of the easiest ways to determine the magnetic field direction is via polarization of radiation resulting from extinction or/and emission by aligned dust grains. Reliability of interpretation of the polarization maps in terms of magnetic fields depends on how well we understand the grain-alignment theory. Explaining what makes grains aligned has been one of the big issues of the modern astronomy. Numerous exciting physical effects have been discovered in the course of research undertaken in this field. As both the theory and observations matured, it became clear that the grain-alignment phenomenon is inherent not only in diffuse interstellar medium or molecular clouds but also is a generic property of the dust in circumstellar regions, interplanetary space and cometary comae. Currently the grain-alignment theory is a predictive one, and its results nicely match observations. Among its predictions is a subtle phenomenon of radiative torques. This phenomenon, after having stayed in oblivion for many years after its discovery, is currently viewed as the most powerful means of alignment. In this article, I shall review the basic physical processes involved in grain alignment, and the currently known mechanisms of alignment. I shall also discuss possible niches for different alignment mechanisms. I shall dwell on the importance of the concept of grain helicity for understanding of many properties of grain alignment, and shall demonstrate that rather arbitrarily shaped grains exhibit helicity when they interact with gaseous and radiative flows

  18. Measurements of magnetic field alignment

    International Nuclear Information System (INIS)

    Kuchnir, M.; Schmidt, E.E.

    1987-01-01

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

  19. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    2001-05-01

    precipitation (AO is mapped to the dawn periphery of the Central Plasma Sheet (CPS; the soft small scale structured precipitation (SSSL is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL. In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA, are observed. The ion energies decrease with increasing latitude. The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM. In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1 and flow out at the AO or DAZ latitudes (Region 2. In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2. In the SSSL, there is anti-sunward convection; in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By . It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996, for the nightside sector of the auroral oval to the dawn sector.Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; plasma convection

  20. Structure of the auroral precipitation region in the dawn sector: relationship to convection reversal boundaries and field-aligned currents

    Directory of Open Access Journals (Sweden)

    Y. I. Feldstein

    electrons and isotropic ion precipitation (AO is mapped to the dawn periphery of the Central Plasma Sheet (CPS; the soft small scale structured precipitation (SSSL is mapped to the outer magnetosphere close to the magnetopause, i.e. the Low Latitude Boundary Layer (LLBL. In the near-noon sector, earthward fluxes of soft electrons, which cause the Diffuse Red Aurora (DRA, are observed. The ion energies decrease with increasing latitude. The plasma spectra of the DRA regime are analogous to the spectra of the Plasma Mantle (PM. In the dawn sector, the large-scale field-aligned currents flow into the ionosphere at the SSSL latitudes (Region 1 and flow out at the AO or DAZ latitudes (Region 2. In the dawn and dusk sectors, the large-scale Region 1 and Region 2 FAC generation occurs in different plasma domains of the distant magnetosphere. The dawn and dusk FAC connection to the traditional Region 1 and Region 2 has only formal character, as FAC generating in various magnetospheric plasma domains integrate in the same region (Region 1 or Region 2. In the SSSL, there is anti-sunward convection; in the DAZ and the AO, there is the sunward convection. At PM latitudes, the convection is controlled by the azimuthal IMF component (By . It is suggested to extend the notation of the plasma pattern boundaries, as proposed by Newell et al. (1996, for the nightside sector of the auroral oval to the dawn sector.

    Key words. Magnetospheric physics (current systems; magnetospheric configuration and dynamics; plasma convection

  1. An auroral westward flow channel (AWFC and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations

    Directory of Open Access Journals (Sweden)

    M. L. Parkinson

    2007-02-01

    Full Text Available An auroral westward flow channel (AWFC is a latitudinally narrow channel of unstable F-region plasma with intense westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to overlap the equatorward edge of the auroral oval, and their life cycle is often synchronised to that of substorms: they commence close to substorm expansion phase onset, intensify during the expansion phase, and then decay during the recovery phase. Here we define for the first time the relationship between an AWFC, large-scale field-aligned current (FAC, the ring current, and plasmapause location. The Tasman International Geospace Environment Radar (TIGER, a Southern Hemisphere HF SuperDARN radar, observed a jet-like AWFC during ~08:35 to 13:28 UT on 7 April 2001. The initiation of the AWFC was preceded by a band of equatorward expanding ionospheric scatter (BEES which conveyed an intense poleward electric field through the inner plasma sheet. Unlike previous AWFCs, this event was not associated with a distinct substorm surge; rather it occurred during an interval of persistent, moderate magnetic activity characterised by AL~−200 nT. The four Cluster spacecraft had perigees within the dusk sector plasmasphere, and their trajectories were magnetically conjugate to the radar observations. The Waves of High frequency and Sounder for Probing Electron density by Relaxation (WHISPER instruments on board Cluster were used to identify the plasmapause location. The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE EUV experiment also provided global-scale observations of the plasmapause. The Cluster fluxgate magnetometers (FGM provided successive measurements specifying the relative location of the ring current and filamentary plasma sheet current. An analysis of Iridium spacecraft magnetometer measurements provided estimates of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows in the AWFC were located close to the peak of a Region 2

  2. Are small-scale field-aligned currents and magneto sheath-like particle precipitation signatures of the same low-altitude cusp?

    DEFF Research Database (Denmark)

    Watermann, J.; Stauning, P.; Luhr, H.

    2009-01-01

    We examined some 75 observations from the low-altitude Earth orbiting DMSP, Orsted and CHAMP satellites which were taken in the region of the nominal cusp. Our objective was to determine whether the actually observed cusp locations as inferred from magnetosheath-like particle precipitation...... ("particle cusp") and intense small-scale magnetic field variations ("current cusp"), respectively, were identical and were consistent with the statistically expected latitude of the cusp derived from a huge number of charged particle spectrograms ("statistical cusp"). The geocentric coordinates...... of the satellites were converted into AACGM coordinates, and the geomagnetic latitude of the cusp boundaries (as indicated by precipitating particles and small-scale field-aligned currents) set in relation to the IMF-B-z dependent latitude of the equatorward boundary of the statistical cusp. We find...

  3. SWMF simulation of field-aligned currents for a varying northward and duskward IMF with nonzero dipole tilt

    Directory of Open Access Journals (Sweden)

    H. Wang

    2008-06-01

    Full Text Available This study concentrates on the FACs distribution for the varying northward and duskward interplanetary magnetic field (IMF conditions when the dipole tilt is nonzero. A global MHD simulation (the Space Weather Modeling Framework, SWMF has been used to perform this study. Hemispheric asymmetry of the time evolution of northward IMF Bz (NBZ FACs is found. As the IMF changes from strictly northward to duskward, NBZ FACs shift counterclockwise in both summer and winter hemispheres. However, in the winter hemisphere, the counterclockwise rotation prohibits the duskward NBZ FACs from evolving into the midday R1 FACs. The midday R1 FACs seem to be an intrusion of dawnside R1 FACs. In the summer hemisphere, the NBZ FACs can evolve into the DPY FACs, consisting of the midday R0 and R1 FACs, after the counterclockwise rotation. The hemispheric asymmetry is due to the fact that the dipole tilt favors more reconnection between the IMF and the summer magnetosphere. When mapping the NBZ and DPY FACs into the magnetosphere it is found that the NBZ currents are located on both open and closed field lines, irrespective of the IMF direction. For the DPY FACs the hemispheric asymmetry emerges: the midday R1 FACs and a small part of R0 FACs are on closed field lines in the winter hemisphere, while a small part of the midday R1 FACs and all the R0 FACs are on open field lines in the summer hemisphere. Both IMF By and dipole tilt cause the polar cap hemispheric and local time asymmetric. When the IMF is northward, the summer polar cap is closed on the nightside while the winter polar cap is open. The polar cap boundary tends to move equatorward as the IMF rotates from northward to duskward, except in the summer hemisphere, the polar cap on the dawnside shifts poleward when the clock angle is less than 10°. The further poleward displacement of the polar cap boundary on one oval side is caused by the twist of the tail plasma sheet, which is in accordance with the

  4. Nanofabrication of Arrays of Silicon Field Emitters with Vertical Silicon Nanowire Current Limiters and Self-Aligned Gates

    Science.gov (United States)

    2016-08-19

    limiters, MEMS, NEMS, field emission, cold cathodes (Some figures may appear in colour only in the online journal) 1. Introduction Dense arrays of silicon... attention has been given to densely packed, highly ordered, top-down fabricated, single crystal vertical silicon nanowire devices that are embedded

  5. Euler potentials for two layers with non-constant current densities in the ambient magnetic field aligned to the layers

    Czech Academy of Sciences Publication Activity Database

    Vandas, Marek; Romashets, E.

    2016-01-01

    Roč. 34, č. 12 (2016), s. 1165-1173 ISSN 0992-7689 R&D Projects: GA ČR(CZ) GA14-19376S Institutional support: RVO:67985815 Keywords : magnetospheric physics * scale birkeland currents * charged particles Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 1.610, year: 2016

  6. Ionospheric conductivity dependence of dayside region-0, 1, and 2 field-aligned current systems: statistical study with DMSP-F7

    Directory of Open Access Journals (Sweden)

    K. Haraguchi

    2004-09-01

    Full Text Available The present study statistically examines the dependence of the intensities of dayside (MLT=8-12h large-scale field-aligned currents (FACs on the ionospheric conductance using the summary data of DMSP-F7 constructed by the procedure of Higuchi and Ohtani (2000. We have found that, in the dayside region, R1 and R0 have a higher correlation between ionospheric conductivity and FAC intensity than R2, suggesting that R0 and R1 are driven by a more voltage-like source than R2. This result is consistent with the idea that R1 and R0 are driven by the interaction between the solar wind and the open magnetospheric magnetic field. We have also found that dayside FAC intensities are latitudinally well balanced when they have a three sheet structure (R0, R1 and R2; on the other hand, for a two sheet structure (R1 and R2, the intensity of R1 is larger than that of R2, so that the net current has the polarity of R1.

  7. Aligning molecules with intense nonresonant laser fields

    DEFF Research Database (Denmark)

    Larsen, J.J.; Safvan, C.P.; Sakai, H.

    1999-01-01

    Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and the molecular polarizability. We demonstrate the general applicability of the scheme by aligning I2, ICl, CS2, CH3I, and C6H5I molecules. The alignment is probed...... by mass selective two dimensional imaging of the photofragment ions produced by femtosecond laser pulses. Calculations on the degree of alignment of I2 are in good agreement with the experiments. We discuss some future applications of laser aligned molecules....

  8. Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

    Directory of Open Access Journals (Sweden)

    A. A. Namgaladze

    Full Text Available The seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF By < 0. In the first variant, the model input data for the summer and winter precipitating fluxes and field-aligned currents have been taken as geomagnetically symmetric and equal to those used earlier in the calculations for the equinoctial conditions. It has been found that both ionospheric and thermospheric disturbances are more intensive in the winter cusp region due to the lower conductivity of the winter polar cap ionosphere and correspondingly larger electric field variations leading to the larger Joule heating effects in the ion and neutral gas temperature, ion drag effects in the thermospheric winds and ion drift effects in the F2-region electron concentration. In the second variant, the calculations have been performed for the events of 28–29 January, 1992 when precipitations were weaker but the magnetospheric convection was stronger than in the first variant. Geomagnetically asymmetric input data for the summer and winter precipitating fluxes and field-aligned currents have been taken from the patterns derived by combining data obtained from the satellite, radar and ground magnetometer observations for these events. Calculated patterns of the ionospheric convection and thermospheric circulation have been compared with observations and it has been established that calculated patterns of the ionospheric convection for both winter and summer hemispheres are in a good agreement with the observations. Calculated patterns of the thermospheric circulation are in a good agreement with the average circulation for the Southern (summer Hemisphere obtained

  9. Quantifying the relationship between the plasmapause and the inner boundary of small-scale field-aligned currents, as deduced from Swarm observations

    Science.gov (United States)

    Heilig, Balázs; Lühr, Hermann

    2018-04-01

    This paper presents a statistical study of the equatorward boundary of small-scale field-aligned currents (SSFACs) and investigates the relation between this boundary and the plasmapause (PP). The PP data used for validation were derived from in situ electron density observations of NASA's Van Allen Probes. We confirmed the findings of a previous study by the same authors obtained from the observations of the CHAMP satellite SSFAC and the NASA IMAGE satellite PP detections, namely that the two boundaries respond similarly to changes in geomagnetic activity, and they are closely located in the near midnight MLT sector, suggesting a dynamic linkage. Dayside PP correlates with the delayed time history of the SSFAC boundary. We interpreted this behaviour as a direct consequence of co-rotation: the new PP, formed on the night side, propagates to the dayside by rotating with Earth. This finding paves the way toward an efficient PP monitoring tool based on an SSFAC index derived from vector magnetic field observations at low-Earth orbit.

  10. STAR/SVT alignment within a finite magnetic field

    International Nuclear Information System (INIS)

    Barannikova, O.Yu.; Belaga, V.V.; Ososkov, G.A.; Panebrattsev, Yu.A.; Bellweid, R.K.; Pruneau, C.A.; Wilson, W.K.

    1999-01-01

    We report on the development of SVT (Silicon Vertex Tracker) software for the purpose of the SVT and TPC (Time Projection Chamber) relative alignment as well as the internal alignment of the SVT components. The alignment procedure described complements the internal SVT alignment procedure discussed in Star Note 356. It involves track reconstruction in both the Star TPC and SVT for the calibration of the SVT geometry in the presence of a finite magnetic field. This new software has been integrated under the package SAL already running under STAR. Both the implementation and the performance of the alignment algorithm are described. We find that the current software implementation in SAL should enable a very satisfactory internal SVT alignment as well as an excellent SVT to TPC relative alignment

  11. Magnetic field-aligned particle precipitation

    International Nuclear Information System (INIS)

    Carlson, W.

    1985-01-01

    Magnetic field-aligned particle fluxes are a common auroral phenomenon. Precipitating field-aligned electrons are seen in the vicinity of auroral arcs as suprathermal bursts, as well as superimposed on the more isotropic inverted V electron precipitation. Electron distribution functions reveal two distinct source populations for the inverted V and field-aligned electron components, and also suggest possible acceleration mechanisms. The inverted V electrons are a hot, boundary plasma sheet population that gains the full parallel acceleration. The field-aligned component appears to originate from cold ionospheric electrons that may be distributed throughout the acceleration region. A turbulent parallel field might explain the apparent lifetime of cold electrons in the acceleration region

  12. Lower Hybrid Drift Waves and Electromagnetic Electron Space-Phase Holes Associated With Dipolarization Fronts and Field-Aligned Currents Observed by the Magnetospheric Multiscale Mission During a Substorm

    Science.gov (United States)

    Le Contel, O.; Nakamura, R.; Breuillard, H.; Argall, M. R.; Graham, D. B.; Fischer, D.; Retinò, A.; Berthomier, M.; Pottelette, R.; Mirioni, L.; Chust, T.; Wilder, F. D.; Gershman, D. J.; Varsani, A.; Lindqvist, P.-A.; Khotyaintsev, Yu. V.; Norgren, C.; Ergun, R. E.; Goodrich, K. A.; Burch, J. L.; Torbert, R. B.; Needell, J.; Chutter, M.; Rau, D.; Dors, I.; Russell, C. T.; Magnes, W.; Strangeway, R. J.; Bromund, K. R.; Wei, H. Y.; Plaschke, F.; Anderson, B. J.; Le, G.; Moore, T. E.; Giles, B. L.; Paterson, W. R.; Pollock, C. J.; Dorelli, J. C.; Avanov, L. A.; Saito, Y.; Lavraud, B.; Fuselier, S. A.; Mauk, B. H.; Cohen, I. J.; Turner, D. L.; Fennell, J. F.; Leonard, T.; Jaynes, A. N.

    2017-12-01

    We analyze two ion scale dipolarization fronts associated with field-aligned currents detected by the Magnetospheric Multiscale mission during a large substorm on 10 August 2016. The first event corresponds to a fast dawnward flow with an antiparallel current and could be generated by the wake of a previous fast earthward flow. It is associated with intense lower hybrid drift waves detected at the front and propagating dawnward with a perpendicular phase speed close to the electric drift and the ion thermal velocity. The second event corresponds to a flow reversal: from southwward/dawnward to northward/duskward associated with a parallel current consistent with a brief expansion of the plasma sheet before the front crossing and with a smaller lower hybrid drift wave activity. Electromagnetic electron phase-space holes are detected near these low-frequency drift waves during both events. The drift waves could accelerate electrons parallel to the magnetic field and produce the parallel electron drift needed to generate the electron holes. Yet we cannot rule out the possibility that the drift waves are produced by the antiparallel current associated with the fast flows, leaving the source for the electron holes unexplained.

  13. Interplanetary magnetic field Bx component influence on horizontal and field‐aligned currents in the ionosphere

    DEFF Research Database (Denmark)

    Laundal, K. M.; Reistad, J. P.; Finlay, C. C.

    2018-01-01

    a detailed investigation of three different sets of magnetic field measurements, from the CHAMP and Swarm low‐Earth‐Orbit satellites, from the AMPERE products derived from the Iridium satellite constellation, and from the SuperMAG ground magnetometer network, each analyzed using different techniques, to test...

  14. Relationships between the Birkeland currents, ionospheric currents, and electric fields

    International Nuclear Information System (INIS)

    Bleuler, E.; Li, C.H.; Nisbet, J.S.

    1982-01-01

    Calculations are made of the currents and electric fields in the ionosphere by using a global model of the electron densities including conjugate coupling along field lines. Incoherent scatter and rocket measurements of high-latitude electron densities have been used to derive realistic variations of the polar conductivities as a function of magnetic activity. The Birkeland currents have been specified in terms of three indices, the total current into and out of the hemisphere, the ratio of the magnitudes of the currents in the AM and PM sectors, R/sub ap/ , and R 12 , the ratio of the magnitudes of the currents in region 1 and 2. The relationship between these parameters of the Birkeland current systems and the auroral electrojet indices AE, AL, and AU is examined as well as the polar cap potential and the electric field at lower latitudes. The cusp currents have been modeled in relation to the interplanetary magnetic field and calculations are given of their effect on electric field and current patterns. One aim of this study is to produce a mathematical model of the currents, electric fields and energy inputs produced by field aligned currents that is consistent with, and specifiable in terms of, measured geophysical indices

  15. Electric field mapping and auroral Birkeland currents

    International Nuclear Information System (INIS)

    Kaufmann, R.L.; Larson, D.J.

    1989-01-01

    Magnetic field lines, electric fields and equipotentials have been mapped throughout the magnetosphere in the vicinity of strong Birkeland currents. It was found that a uniform electric field at either the ionospheric or the equatorial end of a field line can map to a highly structured field at the other end if strong Birkeland currents are located nearby. The initiation of sheet currents of the region 1 - region 2 scale size and intensity resulted in magnetic field line displacements of about 1/2 hour in local time between equatorial and ionospheric end points. As a result, a uniform dawn to dusk electric field at the equator mapped to an ionospheric electric field with strong inward pointing components in the dusk hemisphere. Similar distortions were produced by Birkeland currents associated with narrow east-west-aligned auroral arcs. A specific model for the auroral current system, based on ionospheric measurements during a large substorm, was used to study effects seen during disturbed periods. An iterative procedure was developed to generate a self-consistent current system even in the presence of highly twisted field lines. The measured ionospheric electric field was projected tot he equatorial plane in the presence of the model Birkeland current system. Several physical processes were seen to influence ionospheric and equatorial electric fields, and the associated plasma convection, during a substorm

  16. Vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi; Zhao, Chao; Wang, Qingxiao; Zhang, Qiang; Wang, Zhihong; Zhang, Xixiang; Abutaha, Anas I.; Alshareef, Husam N.

    2012-01-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed

  17. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa

    2010-04-29

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  18. Field Emission of ITO-Coated Vertically Aligned Nanowire Array.

    KAUST Repository

    Lee, Changhwa; Lee, Seokwoo; Lee, Seung S

    2010-01-01

    An indium tin oxide (ITO)-coated vertically aligned nanowire array is fabricated, and the field emission characteristics of the nanowire array are investigated. An array of vertically aligned nanowires is considered an ideal structure for a field emitter because of its parallel orientation to the applied electric field. In this letter, a vertically aligned nanowire array is fabricated by modified conventional UV lithography and coated with 0.1-μm-thick ITO. The turn-on electric field intensity is about 2.0 V/μm, and the field enhancement factor, β, is approximately 3,078 when the gap for field emission is 0.6 μm, as measured with a nanomanipulator in a scanning electron microscope.

  19. Electric field-induced astrocyte alignment directs neurite outgrowth.

    Science.gov (United States)

    Alexander, John K; Fuss, Babette; Colello, Raymond J

    2006-05-01

    The extension and directionality of neurite outgrowth are key to achieving successful target connections during both CNS development and during the re-establishment of connections lost after neural trauma. The degree of axonal elongation depends, in large part, on the spatial arrangement of astrocytic processes rich in growth-promoting proteins. Because astrocytes in culture align their processes on exposure to an electrical field of physiological strength, we sought to determine the extent to which aligned astrocytes affect neurite outgrowth. To this end, dorsal root ganglia cells were seeded onto cultured rat astrocytes that were pre-aligned by exposure to an electric field of physiological strength (500 mV mm(-1)). Using confocal microscopy and digital image analysis, we found that neurite outgrowth at 24 hours and at 48 hours is enhanced significantly and directed consistently along the aligned astrocyte processes. Moreover, this directed neurite outgrowth is maintained when grown on fixed, aligned astrocytes. Collectively, these results indicate that endogenous electric fields present within the developing CNS might act to align astrocyte processes, which can promote and direct neurite growth. Furthermore, these results demonstrate a simple method to produce an aligned cellular substrate, which might be used to direct regenerating neurites.

  20. Markov random field based automatic image alignment for electron tomography.

    Science.gov (United States)

    Amat, Fernando; Moussavi, Farshid; Comolli, Luis R; Elidan, Gal; Downing, Kenneth H; Horowitz, Mark

    2008-03-01

    We present a method for automatic full-precision alignment of the images in a tomographic tilt series. Full-precision automatic alignment of cryo electron microscopy images has remained a difficult challenge to date, due to the limited electron dose and low image contrast. These facts lead to poor signal to noise ratio (SNR) in the images, which causes automatic feature trackers to generate errors, even with high contrast gold particles as fiducial features. To enable fully automatic alignment for full-precision reconstructions, we frame the problem probabilistically as finding the most likely particle tracks given a set of noisy images, using contextual information to make the solution more robust to the noise in each image. To solve this maximum likelihood problem, we use Markov Random Fields (MRF) to establish the correspondence of features in alignment and robust optimization for projection model estimation. The resulting algorithm, called Robust Alignment and Projection Estimation for Tomographic Reconstruction, or RAPTOR, has not needed any manual intervention for the difficult datasets we have tried, and has provided sub-pixel alignment that is as good as the manual approach by an expert user. We are able to automatically map complete and partial marker trajectories and thus obtain highly accurate image alignment. Our method has been applied to challenging cryo electron tomographic datasets with low SNR from intact bacterial cells, as well as several plastic section and X-ray datasets.

  1. Three dimensional alignment of molecules using elliptically polarized laser fields

    DEFF Research Database (Denmark)

    Larsen, J.J.; Bjerre, N.; Hald, K.

    2000-01-01

    We demonstrate, theoretically and experimentally, that an intense, elliptically polarized, nonresonant laser field can simultaneously force all three axes of a molecule to align along given axes fixed in space, thus inhibiting the free rotation in all three Euler angles. Theoretically, the effect...

  2. Waferscale assembly of Field-Aligned nanotube Networks (FANs)

    DEFF Research Database (Denmark)

    Dimaki, Maria; Bøggild, Peter

    2006-01-01

    We demonstrate the integration of nanotube networks on 512 individual devices on a full 4-inch wafer in less than 60 seconds with a roughly 80% yield using dielectrophoresis. We present here investigations of the morphology and electrical resistance of such field aligned networks for different fr...

  3. Remote field eddy current testing

    International Nuclear Information System (INIS)

    Cheong, Y. M.; Jung, H. K.; Huh, H.; Lee, Y. S.; Shim, C. M.

    2001-03-01

    The state-of-art technology of the remote field eddy current, which is actively developed as an electromagnetic non-destructive testing tool for ferromagnetic tubes, is described. The historical background and recent R and D activities of remote-field eddy current technology are explained including the theoretical development of remote field eddy current, such as analytical and numerical approach, and the results of finite element analysis. The influencing factors for actual applications, such as the effect of frequency, magnetic permeability, receiving sensitivity, and difficulties of detection and classification of defects are also described. Finally, two examples of actual application, 1) the gap measurement between pressure tubes and calandria tube in CANDU reactor and, 2) the detection of defects in the ferromagnetic heat exchanger tubes, are described. The future research efforts are also included

  4. Design of a magnetic field alignment diagnostic for the MFTF-B magnet system

    International Nuclear Information System (INIS)

    Deadrick, F.J.; House, P.A.; Frye, R.W.

    1985-01-01

    Magnet alignment in tandem mirror fusion machines plays a crucial role in achieving and maintaining plasma confinement. Various visual alignment tools have been described by Post et al. to align the Tara magnet system. We have designed and installed a remotely operated magnetic field alignment (MFA) diagnostic system as a part of the Mirror Fusion Test Facility (MFTF-B). It measures critical magnetic field alignment parameters of the MFTF-B coil set while under full-field operating conditions. The MFA diagnostic employs a pair of low-energy, electron beam guns on a remotely positionable probe to trace and map selected magnetic field lines. An array of precision electrical detector paddles locates the position of the electron beam, and thus the magnetic field line, at several critical points. The measurements provide a means to compute proper compensating currents to correct for mechanical misalignments of the magnets with auxiliary trim coils if necessary. This paper describes both the mechanical and electrical design of the MFA diagnostic hardware

  5. Generation of macroscopic magnetic-field-aligned electric fields by the convection surge ion acceleratiom mechanism

    International Nuclear Information System (INIS)

    Mauk, B.H.

    1989-01-01

    The ''convection surge'' computer model presented previously (concerning the dramatic, nonadiabatic, magnetic-field-aligned energization of ions near the Earth's geosynchronous orbit in the presence of strong, transient, magnetic-field-perpendicular inductive electric fields) has been extended to include the self-consistent generation of magnetic-field-aligned electric fields. The field-aligned electric potential is obtained by imposing the quasi-neutrality condition using approximated electron distribution forms. The ions are forced to respond self-consistently to this potential. It is found that field-aligned potential drops up to 1 to 10 kV can be generated depending on electron temperatures and on the mass species of the ions. During transient periods of the process, these large potential drops can be confined to a few degrees of magnetic latitude at positions close to the magnetic equator. Anomalous, sometimes dramatic, additional magnetic-field-aligned ion acceleration also occurs in part as a result of a quasi-resonance between the parallel velocities of some ions and the propagating electric potential fronts. It is speculated that the convection surge mechanism could be a key player in the transient, field-aligned electromagnetic processes observed to operate within the middle (e.g., geosynchronous) magnetosphere. copyright American Geophysical Union 1989

  6. Field emission from vertically aligned few-layer graphene

    International Nuclear Information System (INIS)

    Malesevic, Alexander; Kemps, Raymond; Vanhulsel, Annick; Chowdhury, Manish Pal; Volodin, Alexander; Van Haesendonck, Chris

    2008-01-01

    The electric field emission behavior of vertically aligned few-layer graphene was studied in a parallel plate-type setup. Few-layer graphene was synthesized in the absence of any metallic catalyst by microwave plasma enhanced chemical vapor deposition with gas mixtures of methane and hydrogen. The deposit consists of nanostructures that are several micrometers wide, highly crystalline stacks of four to six atomic layers of graphene, aligned vertically to the substrate surface in a high density network. The few-layer graphene is found to be a good field emitter, characterized by turn-on fields as low as 1 V/μm and field amplification factors up to several thousands. We observe a clear dependence of the few-layer graphene field emission behavior on the synthesis parameters: Hydrogen is identified as an efficient etchant to improve field emission, and samples grown on titanium show lower turn-on field values and higher amplification factors when compared to samples grown on silicon

  7. No alignment of cattle along geomagnetic field lines found

    OpenAIRE

    Hert, J.; Jelinek, L.; Pekarek, L.; Pavlicek, A.

    2011-01-01

    This paper presents a study of the body orientation of domestic cattle on free pastures in several European states, based on Google satellite photographs. In sum, 232 herds with 3412 individuals were evaluated. Two independent groups participated in our study and came to the same conclusion that, in contradiction to the recent findings of other researchers, no alignment of the animals and of their herds along geomagnetic field lines could be found. Several possible reasons for this discrepanc...

  8. Electric field-induced astrocyte alignment directs neurite outgrowth

    OpenAIRE

    ALEXANDER, JOHN K.; FUSS, BABETTE; COLELLO, RAYMOND J.

    2006-01-01

    The extension and directionality of neurite outgrowth are key to achieving successful target connections during both CNS development and during the re-establishment of connections lost after neural trauma. The degree of axonal elongation depends, in large part, on the spatial arrangement of astrocytic processes rich in growth-promoting proteins. Because astrocytes in culture align their processes on exposure to an electrical field of physiological strength, we sought to determine the extent t...

  9. To What Extent Does Current Scientific Research and Textbook Content Align? A Methodology and Case Study

    Science.gov (United States)

    Bierema, Andrea M.-K.; Schwartz, Renee S.; Gill, Sharon A.

    2017-01-01

    Recent calls for reform in education recommend science curricula to be based on central ideas instead of a larger number of topics and for alignment between current scientific research and curricula. Because alignment is rarely studied, especially for central ideas, we developed a methodology to discover the extent of alignment between primary…

  10. Optical currents in vector fields

    DEFF Research Database (Denmark)

    Angelsky, O. V.; Gorsky, M. P.; Maksimyak, P. P.

    2011-01-01

    The influence of phase relations and the degree of mutual coherence of superimposing waves in the arrangements of twowave superposition on the characteristics of the microparticle's motion has been analyzed. The prospects of studying temporal coherence using the proposed approach are made. For th....... For the first time, we have shown experimentally the possibility of diagnostics the optical currents in liquids caused by polarization characteristics of an optical field alone, using test metallic particles of nanoscale....

  11. Comprehensive simulation study on local and global development of auroral arcs and field-aligned potentials

    International Nuclear Information System (INIS)

    Watanabe, Tomohiko; Oya, Hiroshi; Watanabe, Kunihiko; Sato, Tetsuya.

    1992-10-01

    Extensive three-dimensional computer simulations of the magnetosphere-ionosphere (M-I) coupling are performed to study self-excitation of auroral arcs with special emphasis on 1) nonlinear evolution of the feedback instability in the M-I coupling system, 2) controlling mechanisms of the auroral arc structure, 3) formation of a field-aligned electric potential structure in association with the development of the feedback instability, and 4) effects of the parallel potential generation on auroral arc development. It is reconfirmed that the feedback instability produces a longitudinally elongated, latitudinally striated structure where the upward field-aligned current and the ionospheric density are locally enhanced. The following important new features are revealed. 1) The global distribution of the striation structure is primarily governed by the magnetospheric convection pattern and the ionospheric density distribution. 2) There appears a significant dawn-dusk asymmetry in the auroral arc formation, even though the apparent geometrical relationship is symmetric. 3) The recombination effect plays a significant role in the global, as well as local, development of the auroral arc structure. The nonlinearity of recombination, in conjunction with the closure of an arc-associated local field-aligned current system, acts to destroy an old arc and creates a new arc in a different but adjacent position. 4) A V-shaped field aligned potential structure is created in association with an auroral arc. Rapid increase in the electron density and the local upward field-aligned current of an arc arises as a result of enhanced ionization by precipitating electrons accelerated by the parallel potential. 5) A drastic oscillatory behavior of appearance and disappearance of auroral arcs is obtained when the ionization effect is strong. The period is primarily given by the Alfven bounce time. (J.P.N.)

  12. Electric-field-induced flow-aligning state in a nematic liquid crystal.

    Science.gov (United States)

    Fatriansyah, Jaka Fajar; Orihara, Hiroshi

    2015-04-01

    The response of shear stress to a weak ac electric field as a probe is measured in a nematic liquid crystal under shear flow and dc electric fields. Two states with different responses are clearly observed when the dc electric field is changed at a constant shear rate: the flow aligning and non-flow aligning states. The director lies in the shear plane in the flow aligning state and out of the plane in the non-flow aligning state. Through application of dc electric field, the non-flow aligning state can be changed to the flow aligning state. In the transition from the flow aligning state to the non-flow aligning state, it is found that the response increases and the relaxation time becomes longer. Here, the experimental results in the flow aligning state are discussed on the basis of the Ericksen-Leslie theory.

  13. Magnetohydrodynamic Ekman layers with field-aligned flow

    Energy Technology Data Exchange (ETDEWEB)

    Nunez, Manuel, E-mail: mnjmhd@am.uva.es [Departamento de Analisis Matematico, Universidad de Valladolid, 47005 Valladolid (Spain)

    2011-05-01

    The Ekman layer in a conducting fluid with constant angular velocity, provided with a magnetic field aligned with the flow, is studied here. The existence of solutions to the magnetohydrodynamic linearized equations depends on the balance between viscosity and resistivity, on the one hand, and the angular and Alfven velocities, on the other. In most cases, exponentially decreasing solutions exist, although their longitudinal oscillations do not need to be periodic. One of the instances without a solution is explained by the presence of Alfven waves traveling backwards along the streamlines.

  14. Tuning vertical alignment and field emission properties of multi-walled carbon nanotube bundles

    Science.gov (United States)

    Sreekanth, M.; Ghosh, S.; Srivastava, P.

    2018-01-01

    We report the growth of vertically aligned carbon nanotube bundles on Si substrate by thermal chemical vapor deposition technique. Vertical alignment was achieved without any carrier gas or lithography-assisted deposition. Growth has been carried out at 850 °C for different quantities of solution of xylene and ferrocene ranging from 2.25 to 3.00 ml in steps of 0.25 ml at a fixed concentration of 0.02 gm (ferrocene) per ml. To understand the growth mechanism, deposition was carried out for different concentrations of the solution by changing only the ferrocene quantity, ranging from 0.01 to 0.03 gm/ml. A tunable vertical alignment of multi-walled carbon nanotubes (CNTs) has been achieved by this process and examined by scanning and transmission electron microscopic techniques. Micro-crystalline structural analysis has been done using Raman spectroscopy. A systematic variation in field emission (FE) current density has been observed. The highest FE current density is seen for the film grown with 0.02 gm/ml concentration, which is attributed to the better alignment of CNTs, less structural disorder and less entanglement of CNTs on the surface. The alignment of CNTs has been qualitatively understood on the basis of self-assembled catalytic particles.

  15. The effect of Birkeland currents on magnetic field topology

    Science.gov (United States)

    Peroomian, Vahe; Lyons, Larry R.; Schulz, Michael

    1996-01-01

    A technique was developed for the inclusion of large scale magnetospheric current systems in magnetic field models. The region 1 and 2 Birkeland current systems are included in the source surface model of the terrestrial magnetosphere. The region 1 and 2 Birkeland currents are placed in the model using a series of field aligned, infinitely thin wire segments. The normal component of the magnetic field from these currents is calculated on the surface of the magnetopause and shielded using image current carrying wires placed outside of the magnetosphere. It is found that the inclusion of the Birkeland currents in the model results in a northward magnetic field in the near-midnight tail, leading to the closure of previously open flux in the tail, and a southward magnetic field in the flanks. A sunward shift in the separatrix is observed.

  16. Magnetic field alignment for a 20 MeV linear induction accelerator

    International Nuclear Information System (INIS)

    Zhang Wenwei; Pan Haifeng; Li Hong; Liu Yunlong; Zhang Linwen

    2002-01-01

    'Dragon-1' accelerator now is being constructed in CAEP. It will produce high current pulse electron beams. The main components of the accelerator include 72 induction accelerating cells and 18 connection cells with ports for beam di gnostic hardware and vacuum pump. In order to acquire high quality beams, a lot of problems have to be addressed such as to reduce the emittance, to control the increase of corkscrew and so on. The alignment of the focus magnetic field is the most concerned. A laser track has been used for mechanical alignment, magnetic alignment is performed by using pulsed-wire technique, and the natural tilt errors is corrected by a pair of steering coil, which is located inside the cell

  17. Generation mechanisms for magnetic-field-aligned electric fields in the magnetosphere

    International Nuclear Information System (INIS)

    Faelthammar, C.-G.

    1977-09-01

    Magnetic-field-aligned electric fields in the magnetosphere can be generated in several different ways, and in this review some possible mechanisms are presented. Observational data now available indicates that more than one of the mechanisms mentioned are operative in the magnetosphere but it is not yet possible to evaluate their relative importance. (author)

  18. Alignment Exemplars and Current Opportunities for Collaboration ANADP

    OpenAIRE

    Walters, Tyler O.; Greer, Chris; Hartman, Cathy; Skinner, Katherine; Jung, Joachim

    2014-01-01

    Aligning National Approaches to Digital Preservation: An Action Assembly Biblioteca de Catalunya (National Library of Catalonia) November 18-20, 2013, Barcelona, Spain Auburn University Council on Library and Information Resources (CLIR) Digital Curation Centre (DCC) Digital Preservation Network (DPN) Joint Information Systems Committee (JISC) University of North Texas Virginia Tech Interuniversity Consortium for Political and Social Research (ICPSR) Innovative Inte...

  19. Electronic properties of field aligned CrO2 powders

    International Nuclear Information System (INIS)

    Tripathy, D.; Adeyeye, A.O.

    2005-01-01

    We have investigated in detail the electronic transport properties of half metallic CrO 2 powder-based devices, fabricated using optical lithography and field alignment technique. A transition in the conduction mechanism from spin-dependent intergranular tunneling to inelastic hopping was observed at 215 K. This transition temperature shifts to 230 K in the presence of 10 kOe field cooling due to reduction of the spin-independent hopping conductance channel. I-V characteristics exhibit strong temperature dependence and are non-linear even at room temperature. Our experimental results are in good agreement with a simple theoretical model. A novel 'double switching' phenomenon was observed in the I-V curves below the transition temperature

  20. High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

    Science.gov (United States)

    Gupta, Bipin Kumar; Kedawat, Garima; Gangwar, Amit Kumar; Nagpal, Kanika; Kashyap, Pradeep Kumar; Srivastava, Shubhda; Singh, Satbir; Kumar, Pawan; Suryawanshi, Sachin R.; Seo, Deok Min; Tripathi, Prashant; More, Mahendra A.; Srivastava, O. N.; Hahm, Myung Gwan; Late, Dattatray J.

    2018-01-01

    The vertical aligned carbon nanotubes (CNTs)-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si) wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness) as a barrier layer and iron (Fe, 1.5 nm thickness) as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM) images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2-30 walls with an inner diameter of 3-8 nm. Raman spectrum analysis shows G-band at 1580 cm-1 and D-band at 1340 cm-1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm), low turn-on field (0.6 V/μm) and field enhancement factor (6917) with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

  1. High-performance field emission device utilizing vertically aligned carbon nanotubes-based pillar architectures

    Directory of Open Access Journals (Sweden)

    Bipin Kumar Gupta

    2018-01-01

    Full Text Available The vertical aligned carbon nanotubes (CNTs-based pillar architectures were created on laminated silicon oxide/silicon (SiO2/Si wafer substrate at 775 °C by using water-assisted chemical vapor deposition under low pressure process condition. The lamination was carried out by aluminum (Al, 10.0 nm thickness as a barrier layer and iron (Fe, 1.5 nm thickness as a catalyst precursor layer sequentially on a silicon wafer substrate. Scanning electron microscope (SEM images show that synthesized CNTs are vertically aligned and uniformly distributed with a high density. The CNTs have approximately 2–30 walls with an inner diameter of 3–8 nm. Raman spectrum analysis shows G-band at 1580 cm−1 and D-band at 1340 cm−1. The G-band is higher than D-band, which indicates that CNTs are highly graphitized. The field emission analysis of the CNTs revealed high field emission current density (4mA/cm2 at 1.2V/μm, low turn-on field (0.6 V/μm and field enhancement factor (6917 with better stability and longer lifetime. Emitter morphology resulting in improved promising field emission performances, which is a crucial factor for the fabrication of pillared shaped vertical aligned CNTs bundles as practical electron sources.

  2. Vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2012-10-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed on the sidewall of the stack to bridge the source and drain. Both the effective gate dielectric and gate electrode were normal to the substrate surface. The channel length is determined by the dielectric thickness between source and drain electrodes, making it easier to fabricate sub-micrometer transistors without using time-consuming electron beam lithography. The transistor area is much smaller than the planar CNTFET due to the vertical arrangement of source and drain and the reduced channel area. © 2012 Elsevier Ltd. All rights reserved.

  3. Morphologically Aligned Cation-Exchange Membranes by a Pulsed Electric Field for Reverse Electrodialysis.

    Science.gov (United States)

    Lee, Ju-Young; Kim, Jae-Hun; Lee, Ju-Hyuk; Kim, Seok; Moon, Seung-Hyeon

    2015-07-21

    A low-resistance ion-exchange membrane is essential to achieve the high-performance energy conversion or storage systems. The formation methods for low-resistance membranes are various; one of the methods is the ion channel alignment of an ion-exchange membrane under a direct current (DC) electric field. In this study, we suggest a more effective alignment method than the process with the DC electric field. First, an ion-exchange membrane was prepared under a pulsed electric field [alternating current (AC) mode] to enhance the effectiveness of the alignment. The membrane properties and the performance in reverse electrodialysis (RED) were then examined to assess the membrane resistance and ion selectivity. The results show that the membrane electrical resistance (MER) had a lower value of 0.86 Ω cm(2) for the AC membrane than 2.13 Ω cm(2) observed for the DC membrane and 4.30 Ω cm(2) observed for the pristine membrane. Furthermore, RED achieved 1.34 W/m(2) of maximum power density for the AC membrane, whereas that for the DC membrane was found to be 1.14 W/m(2) [a RED stack assembled with CMX, used as a commercial cation-exchange membrane (CEM), showed 1.07 W/m(2)]. Thereby, the novel preparation process for a remarkable low-resistance membrane with high ion selectivity was demonstrated.

  4. Acceleration of auroral particles by magnetic-field aligned electric fields

    International Nuclear Information System (INIS)

    Block, L.P.

    1988-01-01

    Measurements on the S3-3 and Viking satellites appear to show that at least a large fraction of magnetic field-aligned potential drops are made up of multiple double layers. Solitons and double layers in U-shaped potential structures give rise to spiky electric fields also perpendicular to the magnetic field in agreement with satellite measurements. The large scale potential structures associated with inverted V-events are built up of many similar short-lived structures on a small scale. Viking measurements indicate that electric fields parallel to the magnetic field are almost always directed upward

  5. Patterned growth of carbon nanotubes over vertically aligned silicon nanowire bundles for achieving uniform field emission.

    Science.gov (United States)

    Hung, Yung-Jr; Huang, Yung-Jui; Chang, Hsuan-Chen; Lee, Kuei-Yi; Lee, San-Liang

    2014-01-01

    A fabrication strategy is proposed to enable precise coverage of as-grown carbon nanotube (CNT) mats atop vertically aligned silicon nanowire (VA-SiNW) bundles in order to realize a uniform bundle array of CNT-SiNW heterojunctions over a large sample area. No obvious electrical degradation of as-fabricated SiNWs is observed according to the measured current-voltage characteristic of a two-terminal single-nanowire device. Bundle arrangement of CNT-SiNW heterojunctions is optimized to relax the electrostatic screening effect and to maximize the field enhancement factor. As a result, superior field emission performance and relatively stable emission current over 12 h is obtained. A bright and uniform fluorescent radiation is observed from CNT-SiNW-based field emitters regardless of its bundle periodicity, verifying the existence of high-density and efficient field emitters on the proposed CNT-SiNW bundle arrays.

  6. Correlation of ICME Magnetic Fields at Radially Aligned Spacecraft

    Science.gov (United States)

    Good, S. W.; Forsyth, R. J.; Eastwood, J. P.; Möstl, C.

    2018-03-01

    The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east-west and north-south directed components, with Pearson's correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME ( i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors well upstream of the

  7. Field aligned flows driven by neutral puffing at MAST

    Science.gov (United States)

    Waters, I.; Frerichs, H.; Silburn, S.; Feng, Y.; Harrison, J.; Kirk, A.; Schmitz, O.

    2018-06-01

    Neutral deuterium gas puffing at the high field side of the mega ampere spherical tokamak (MAST) is shown to drive carbon impurity flows that are aligned with the trajectory of the magnetic field lines in the plasma scrape-off-layer. These impurity flows were directly imaged with emissions from C2+ ions at MAST by coherence imaging spectroscopy and were qualitatively reproduced in deuterium plasmas by modeling with the EMC3-EIRENE plasma edge fluid and kinetic neutral transport code. A reduced one-dimensional momentum and particle balance shows that a localized increase in the static plasma pressure in front of the neutral gas puff yields an acceleration of the plasma due to local ionization. Perpendicular particle transport yields a decay from which a parallel length scale can be determined. Parameter scans in EMC3-EIRENE were carried out to determine the sensitivity of the deuterium plasma flow phenomena to local fueling and diffusion parameters and it is found that these flows robustly form across a wide variety of plasma conditions. Finally, efforts to couple this behavior in the background plasma directly to the impurity flows observed experimentally in MAST using a trace impurity model are discussed. These results provide insight into the fueling and exhaust features at this pivotal point of the radial and parallel particle flux balance, which is a major part of the plasma fueling and exhaust characteristics in a magnetically confined fusion device.

  8. Growth of vertically aligned arrays of carbon nanotubes for high field emission

    International Nuclear Information System (INIS)

    Kim, D.; Lim, S.H.; Guilley, A.J.; Cojocaru, C.S.; Bouree, J.E.; Vila, L.; Ryu, J.H.; Park, K.C.; Jang, J.

    2008-01-01

    Vertically aligned multi-walled carbon nanotubes have been grown on Ni-coated silicon substrates, by using either direct current diode or triode plasma-enhanced chemical vapor deposition at low temperature (around 620 deg. C). Acetylene gas has been used as the carbon source while ammonia and hydrogen have been used for etching. However densely packed (∼ 10 9 cm -2 ) CNTs were obtained when the pressure was ∼ 100 Pa. The alignment of nanotubes is a necessary, but not a sufficient condition in order to get an efficient electron emission: the growth of nanotubes should be controlled along regular arrays, in order to minimize the electrostatic interactions between them. So a three dimensional numerical simulation has been developed to calculate the local electric field in the vicinity of the tips for a finite square array of nanotubes and thus to calculate the maximum of the electron emission current density as a function of the spacing between nanotubes. Finally the triode plasma-enhanced process combined with pre-patterned catalyst films (using different lithography techniques) has been chosen in order to grow regular arrays of aligned CNTs with different pitches in the micrometer range. The comparison between the experimental and the simulation data permits to define the most efficient CNT-based electron field emitters

  9. Enhanced field emission properties of vertically aligned double-walled carbon nanotube arrays

    International Nuclear Information System (INIS)

    Chen, Guohai; Shin, Dong Hoon; Lee, Cheol Jin; Iwasaki, Takayuki; Kawarada, Hiroshi

    2008-01-01

    Vertically aligned double-walled carbon nanotube (VA-DWCNT) arrays were synthesized by point-arc microwave plasma chemical vapor deposition on Cr/n-Si and SiO 2 /n-Si substrates. The outer tube diameters of VA-DWCNTs are in the range of 2.5-3.8 nm, and the average interlayer spacing is approximately 0.42 nm. The field emission properties of these VA-DWCNTs were studied. It was found that a VA-DWCNT array grown on a Cr/n-Si substrate had better field emission properties as compared with a VA-DWCNT array grown on a SiO 2 /n-Si substrate and randomly oriented DWCNTs, showing a turn-on field of about 0.85 V μm -1 at the emission current density of 0.1 μA cm -2 and a threshold field of 1.67 V μm -1 at the emission current density of 1.0 mA cm -2 . The better field emission performance of the VA-DWCNT array was mainly attributed to the vertical alignment of DWCNTs on the Cr/n-Si substrate and the low contact resistance between CNTs and the Cr/n-Si substrate

  10. Accuracy of field alignment in abdominal radiation therapy

    International Nuclear Information System (INIS)

    Kortmann, R. D.; Hess, C. F.; Meisner, C.; Schmidberger, H.; Bamberg, M.

    1996-01-01

    Purpose: To assess the accuracy of field alignment in a homogeneous group of patients undergoing radiotherapy of the abdomen (adjuvant treatment of the paraaortic region in Stage I testicular seminoma). To evaluate the predictive value of the first verification on field placement errors during subsequent treatment delivery. Methods and Materials: In 45 patients, linear and rotational discrepancies were measured between simulation and first check and between 10 consecutive verification films. Results: For the total group of patients, the distribution of all deviations showed mean values between 2.3 mm and -2.7 mm with standard deviations of 3.9 mm to 4.7 mm for linear discrepancies, and -0.5 deg. to 0.3 deg. with standard deviations of 1.2 deg. to 2.1 deg. for rotational discrepancies, respectively. For all patients, deviations for the transition from simulator to the treatment machine were similar to deviations during subsequent treatment delivery, with 95% of all absolute deviations < 10.0 mm and 4 deg. , respectively. When performing correlation analysis between deviations at first check and during treatment delivery, a correlation for lateral displacements and a borderline correlation for caudal displacements could be found. There was no correlation for cranial and rotational displacements. Conclusions: Although a trend of deviations for subsequent treatment delivery may be shown at first check, our analysis indicates that the first verification cannot reliably predict inaccuracies during treatment delivery. Random fluctuations of field displacements of up to 1.0 cm prevail. They must be considered when prescribing the safety margins of the planned target volume and determining cutoff points for corrective actions in abdominal radiation therapy

  11. Beam alignment based on two-dimensional power spectral density of a near-field image.

    Science.gov (United States)

    Wang, Shenzhen; Yuan, Qiang; Zeng, Fa; Zhang, Xin; Zhao, Junpu; Li, Kehong; Zhang, Xiaolu; Xue, Qiao; Yang, Ying; Dai, Wanjun; Zhou, Wei; Wang, Yuanchen; Zheng, Kuixing; Su, Jingqin; Hu, Dongxia; Zhu, Qihua

    2017-10-30

    Beam alignment is crucial to high-power laser facilities and is used to adjust the laser beams quickly and accurately to meet stringent requirements of pointing and centering. In this paper, a novel alignment method is presented, which employs data processing of the two-dimensional power spectral density (2D-PSD) for a near-field image and resolves the beam pointing error relative to the spatial filter pinhole directly. Combining this with a near-field fiducial mark, the operation of beam alignment is achieved. It is experimentally demonstrated that this scheme realizes a far-field alignment precision of approximately 3% of the pinhole size. This scheme adopts only one near-field camera to construct the alignment system, which provides a simple, efficient, and low-cost way to align lasers.

  12. Electric fields and currents observed by S3-2 in the vicinity of discrete arcs

    International Nuclear Information System (INIS)

    Burke, W.J.

    1984-01-01

    The high time resolution of the electric and magnetic field detectors on the polar orbiting satellite S3-2 made it possible to examine the details of auroral events down to discrete-arc scales. Depending on the instantaneous look direction of an electron detector, information about field-aligned accelerations above the satellite could also be obtained. Case studies of four arc events, three in the auroral oval and one in the polar cap, have been completed. Field-aligned currents associated with arcs in the auroral oval appeared as matched pairs of oppositely directed current sheets. Magnetic deflections, almost exclusively in the east-west direction departed from and returned to baselines established by the large-scale Region 1/Region 2 currents. The upward currents had intensities of up to 145 microamperes/sq m and were carried by electrons that were accelerated through field aligned potential drops. The relationship between the field-aligned current density and potential drop is not inconsistent with predictions of a laminar flow model. The most intense return (downward) currents were in the 10 to 15 microamperes/sq m range. At satellite altitudes near 1000 km, these currents approximate the critical limit for current driven, ion cyclotron instabilities. The arc in the polar cap was sun-aligned and was found in a region of intense convective shear, with the electric field pointing toward the center of the arc. The field-aligned currents consisted of three sheets two with currents flowing into and one out of the ionosphere. The upward current was carried by polar-rain electrons that had undergone a field-aligned acceleration of approximately 1 kV. 19 references

  13. Anomalous foreshock field-aligned beams observed by Cluster

    Directory of Open Access Journals (Sweden)

    K. Meziane

    2011-10-01

    Full Text Available We report occasional observations of two simultaneously distinct ion foreshock components recorded by the Cluster spacecraft upstream of the Earth's bow shock. In most occurrences, the lower-energy population originates as a field-aligned beam (FAB associated with quasi-perpendicular regions, which loses energy as the IMF rotates into oblique geometries. A second beam, with energies in excess of ~10 keV, appears sometimes in association with the onset of ultra-low frequency (ULF waves, and sometimes ahead of the appearance of the latter. Measurements from the mass spectrometer indicate that both beams consist of protons. While the lower-speed beam is well-accounted for by a known reflection mechanism, the non-radial IMF orientations as well as other arguments seem to rule out magnetosheath or magnetospheric sources for the higher energy component. The wave characteristics are typical of the oblique foreshock and we have found that they are in cyclotron-resonance with the low speed beam (FAB. These observations constitute a theoretical challenge since conventional mechanisms described in the literature cannot account for the production of beams at two different energies.

  14. Vertically aligned carbon nanotubes/diamond double-layered structure for improved field electron emission stability

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L., E-mail: qiaoqin.yang@mail.usask.ca; Yang, Q.; Zhang, C.; Li, Y.S.

    2013-12-31

    A double-layered nanostructure consisting of a layer of vertically aligned Carbon Nanotubes (CNTs) and a layer of diamond beneath has been synthesized on silicon substrate by Hot Filament Chemical Vapor Deposition. The synthesis was achieved by first depositing a layer of diamond on silicon and then depositing a top layer of vertically aligned CNTs by applying a negative bias on the substrate holder. The growth of CNTs was catalyzed by a thin layer of spin-coated iron nitride. The surface morphology and structure of the CNTs/diamond double-layered structure were characterized by Scanning Electron Microscope, Energy Dispersive X-ray spectrum, and Raman Spectroscopy. Their field electron emission (FEE) properties were measured by KEITHLEY 237 high voltage measurement unit, showing much higher FEE current stability than single layered CNTs. - Highlights: • A new double-layered nanostructure consisting of a layer of vertically aligned CNTs and a layer of diamond beneath has been synthesized by hot filament chemical vapor deposition. • This double-layered structure exhibits superior field electron emission stability. • The improvement of emission stability is due to the combination of the unique properties of diamond and CNTs.

  15. Merging of magnetic fields with field-aligned plasma flow components

    International Nuclear Information System (INIS)

    Mitchell, H.G. Jr.; Kan, J.R.

    1978-01-01

    The Sonnerup merging model for an incompressible plasma is extended to allow a flow component along the field lines in the inflow regions. Solutions are found to exist as long as the difference between the quantities B. V for the two inflow regions does not exceed a critical magnitude dependent on the inflow field magnitudes and plasma densities. All such solutions satisfy Vasyliunas' definition of merging, but some classes of solution have radically altered geometries, i.e. geometries in which the inflow regions are much smaller than the outflow regions. The necessary but not sufficient condition for these unusual geometries is that the field-aligned flow component in at least one inflow region be super-Alfvenic. A solution for the case of a vacuum field in one inflow region is obtained in which any flow velocity is allowed in the non-vacuum inflow region, although super-Alfvenic flow can still result in an unusual geometry. For symmetric configurations, the usual geometry, that of Petschek and Sonnerup, is retained as long as both field-aligned flow components in the inflow regions are less than twice the inflow Alfven speed. For the case of a vacuum field on one side and fields approximating the boundary between the solar wind and the earth's dayside magnetosphere, the usual geometry is retained for flow less than about 2.5 times the local Alfven speed. (author)

  16. Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Wang, B.B. [College of Chemistry and Chemical Engineering, Chongqing University of Technology, 69 Hongguang Rd, Lijiatuo, Banan District, Chongqing 400054 (China); Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Cheng, Q.J. [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Chen, X. [College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Ostrikov, K., E-mail: kostya.ostrikov@csiro.au [Plasma Nanoscience Centre Australia (PNCA), CSIRO Materials Science and Engineering, P.O. Box 218, Lindfield, NSW 2070 (Australia); Plasma Nanoscience, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

    2011-09-22

    Highlights: > A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. > The carbon nanotubes are later treated with nitrogen plasmas. > The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. > A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 {mu}A/cm{sup 2}) achieved at a low applied field (3.50 V/{mu}m) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

  17. Enhancement of electron field emission of vertically aligned carbon nanotubes by nitrogen plasma treatment

    International Nuclear Information System (INIS)

    Wang, B.B.; Cheng, Q.J.; Chen, X.; Ostrikov, K.

    2011-01-01

    Highlights: → A new and custom-designed bias-enhanced hot-filament chemical vapor deposition system is developed to synthesize vertically aligned carbon nanotubes. → The carbon nanotubes are later treated with nitrogen plasmas. → The electron field emission characteristics of the carbon nanotubes are significantly improved after the nitrogen plasma treatment. → A new physical mechanism is proposed to interpret the improvement of the field emission characteristics. - Abstract: The electron field emission (EFE) characteristics from vertically aligned carbon nanotubes (VACNTs) without and with treatment by the nitrogen plasma are investigated. The VACNTs with the plasma treatment showed a significant improvement in the EFE property compared to the untreated VACNTs. The morphological, structural, and compositional properties of the VACNTs are extensively examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and energy dispersive X-ray spectroscopy. It is shown that the significant EFE improvement of the VACNTs after the nitrogen plasma treatment is closely related to the variation of the morphological and structural properties of the VACNTs. The high current density (299.6 μA/cm 2 ) achieved at a low applied field (3.50 V/μm) suggests that the VACNTs after nitrogen plasma treatment can serve as effective electron field emission sources for numerous applications.

  18. How do current public integrated reports align with the

    NARCIS (Netherlands)

    Hurks, P.; Langendijk, H.P.A.J.; Nandram, K.

    2015-01-01

    This paper examines empirically the current practice with regard to integrated reporting according to the IR Framework among the 104 original participants (companies) of the IIRC Pilot program. We made a selection with respect to these 104 participants based on organization’s stipulation that they

  19. Growth and field emission properties of one-dimensional carbon composite structure consisting of vertically aligned carbon nanotubes and nanocones

    International Nuclear Information System (INIS)

    Zhang Hongxin; Feng, Peter X; Fonseca, Luis; Morell, Gerardo; Makarov, Vladimir I; Weiner, Brad R

    2009-01-01

    A simple approach is demonstrated for quickly growing a large-area aligned carbon composite nanostructure consisting of vertically aligned nanotubes and nanocones by the catalyst-assisted pulsed laser deposition techniques. The pyrolytic graphite was used as carbon source. The carbon nanocones were first grown on the molybdenum substrate with Ni catalysts. The carbon nanotubes have a uniform shape and length, aligned vertically on carbon nanocones, and the average diameter is about 7 nm. The special carbon composite arrays exhibit excellent field emission behaviours. The long-term field emission current stability of the one-dimensioned carbon nanostructure has also been investigated. No obvious current density decay was observed after a 10-day continuous experiment, indicating the super stability of the sample as cathode material.

  20. Vertically aligned zinc selenide nanoribbon arrays: microstructure and field emission

    International Nuclear Information System (INIS)

    Zhao Lijuan; Pang Qi; Cai Yuan; Wang Ning; Ge Weikun; Wang Jiannong; Yang Shihe

    2007-01-01

    Uniform ZnSe precursor (ZnSe : 0.38en, en = ethylenediamine) nanoribbon arrays are grown vertically on Zn foils in ethylenediamine (en) using a solvothermal method. After the annealing treatment in N 2 , the ZnSe nanoribbon arrays can be obtained without an obvious morphology change and the crystallinity of ribbons is greatly improved. The microstructures of both individual ZnSe precursor and ZnSe nanoribbons are investigated. Field emission characteristics show that the onset field required drawing a current density of ∼0.1 μ A cm -2 from the ZnSe nanoribbons is 5.0 V μm -1 and the field enhancement factors are determined to be ∼1382

  1. Requirements for alignment of electron cyclotron current drive for neoclassical tearing mode stabilization in ITER

    International Nuclear Information System (INIS)

    La Haye, R.J.; Ferron, J.R.; Humphreys, D.A.; Luce, T.C.; Petty, C.C.; Prater, R.; Strait, E.J.; Welander, A.S.

    2008-01-01

    ITER will rely on electron cyclotron stabilization of neoclassical tearing mode islands. The large size and low torque applied in ITER imply slow plasma rotation and susceptibility to island locking by the resistive wall; locking is likely to lead to a loss of the high confinement H-mode, a beta collapse and possibly disruption. 'Front' steering of the launcher, with narrower electron cyclotron current drive (ECCD), has resolved the issue in 'remote' steering of the driven current being too broad and relatively ineffective. However, narrower current drive places demands on alignment of the current drive on the rational surface that is being stabilized. DIII-D alignment techniques with and without (preemptive) an island are reviewed. The results are used to check models for the effect of misalignment and are then applied to ITER. Criteria for accuracy of alignment as a function of injected power and for the necessary time response of the controller are presented

  2. The role of magnetic-field-aligned electric fields in auroral acceleration

    International Nuclear Information System (INIS)

    Block, L.P.; Faelthammar, C.G.

    1990-01-01

    Electric field measurements on the Swedish satellite Viking have confirmed and extended earlier observations on S3-3 and provided further evidence of the role of dc electric fields in auroral acceleration processes. On auroral magnetic field lines the electric field is strongly fluctuating both transverse and parallel to the magnetic field. The significance of these fluctuations for the auroral acceleration process is discussed. A definition of dc electric fields is given in terms of their effects on charged particles. Fluctuations below several hertz are experienced as dc by typical auroral electrons if the acceleration length is a few thousand kilometers. For ions the same is true below about 0.1 Hz. The magnetic-field-aligned (as well as the transverse) component of the electric field fluctuations has a maximum below 1 Hz, in a frequency range that appears as dc to the electrons but not to the ions. This allows it to cause a selective acceleration, which may be important in explaining some of the observed characteristics of auroral particle distributions. The electric field observations on Viking support the conclusion that magnetic-field-aligned potential drops play an important role in auroral acceleration, in good agreement with particle observations boht on Viking and on the DE satellites. They also show that a large part, or even all, of the accelerating potential drop may be accounted for by numerous weak (about a volt) electric double layers, in agreement with earlier observations on the S3-3 satellite and with an early theoretical suggestion by L. Block

  3. Local eddy current measurements in pulsed fields

    Energy Technology Data Exchange (ETDEWEB)

    Espina-Hernandez, J.H. [SEPI-Electronica, ESIME-IPN, UPALM Edif. ' Z' . Zacatenco, Mexico DF 07738 (Mexico)], E-mail: jhespina@gmail.com; Groessinger, R. [Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A-1040 Vienna (Austria); Hallen, J.M. [Departamento de Ingenieria Metalurgica, IPN-ESIQIE, UPALM Edif. 7, Zacatenco, Mexico DF 07738 (Mexico)

    2008-07-15

    This work presents new eddy current measurements in pulsed fields. A commercial point pick-up coil is used to detect the induction signal along the radius of Cu and Al samples with cylindrical shape and diameters between 5 and 35 mm. Local eddy current measurements were performed on the surface of conducting materials due to the small dimensions of the coil. A simple electrical circuit, used as a model, is proposed to describe the local eddy current effect in pulsed fields. The proposed model allows to calculate the phase shift angle between the signal proportional to eddy currents and the applied external field in a pulsed field magnetometer.

  4. Field emission from carbon nanotube bundle arrays grown on self-aligned ZnO nanorods

    International Nuclear Information System (INIS)

    Li Chun; Fang Guojia; Yuan Longyan; Liu Nishuang; Ai Lei; Xiang Qi; Zhao Dongshan; Pan Chunxu; Zhao Xingzhong

    2007-01-01

    The field emission (FE) properties of carbon nanotube (CNT) bundle arrays grown on vertically self-aligned ZnO nanorods (ZNRs) are reported. The ZNRs were first synthesized on ZnO-seed-coated Si substrate by the vapour phase transport method, and then the radically grown CNTs were grown directly on the surface of the ZNRs from ethanol flames. The CNT/ZNR composite showed a turn-on field of 1.5 V μm -1 (at 0.1 μA cm -2 ), a threshold field of 4.5 V μm -1 (at 1 mA cm -2 ) and a stable emission current with fluctuations of 5%, demonstrating significantly enhanced FE of ZNRs due to the low work function and high aspect ratio of the CNTs, and large surface-to-volume ratio of the underlying ZNRs

  5. Shock aurora: Field-aligned discrete structures moving along the dawnside oval

    Science.gov (United States)

    Zhou, Xiaoyan; Haerendel, Gerhard; Moen, Jøran I.; Trondsen, Espen; Clausen, Lasse; Strangeway, Robert J.; Lybekk, Bjørn; Lorentzen, Dag A.

    2017-03-01

    Generated by interplanetary shocks or solar wind pressure pulses, shock aurora has transient, global, and dynamic significances and provides a direct manifestation of the solar wind-magnetosphere-ionosphere interaction. As a part of a series of studies of the shock aurora, this paper focuses on the interaction at the morning magnetopause and its auroral manifestation at 06 magnetic local time, where the velocity and magnetic field shears dominate the interaction. Flow shears can generate wave-like structures inside a viscous boundary layer or even larger-scale vortices. These structures couple to the ionosphere via quasi-static field-aligned currents or via kinetic Alfvén waves. Potential drops along field-aligned filaments may be generated accelerating electrons to form auroral manifestations of the structures. A shock aurora event at dawnside is used to test this scenario. The findings include moving auroral streaks/rays that have a vertical profile from red (at 250 km altitude) to purple (at 100 km). The streaks moved antisunward along the poleward boundary of the oval at an ionospheric speed of 3 km s-1. It was mapped to the magnetopause flank at 133 km s-1, which was consistent with the observed speed of the magnetopause surface waves generated by the Kelvin-Helmholtz instability. The calculated field-aligned potential drop using Haerendel's analytic model was 5 kV that reasonably explained the observations. The results support the above scenario and reveal that magnetic and velocity shears at the flanks of the magnetospause may be the main cause of the fast moving shock aurora streaks.

  6. Active feedback stabilization of the flute instability in a mirror machine using field-aligned coils

    International Nuclear Information System (INIS)

    Lifshitz, A.; Be'ery, I.; Fisher, A.; Ron, A.; Fruchtman, A.

    2012-01-01

    A plasma confined in linear mirror machines is unstable even at low β, mainly because of the flute instability. One possible way to stabilize the plasma is to use active feedback to correct the plasma shape in real time. The theoretically investigated apparatus consists of feedback coils aligned with the magnetic field, immersed in a cold plasma around the hot core. When the current through the feedback coils changes, the plasma moves to conserve the magnetic flux via compressional Alfvén waves. An analytical model is used to find a robust feedback algorithm with zero residual currents. It is shown that due to the plasma's rotation, maximal stability is obtained with a large phase angle between the perturbations' modes and the feedback integral-like term. Finally, a two-dimensional MHD simulation implementing the above algorithm in fact shows stabilization of the plasma with zero residual currents. (paper)

  7. Field-free molecular orientation of nonadiabatically aligned OCS

    Science.gov (United States)

    Sonoda, Kotaro; Iwasaki, Atsushi; Yamanouchi, Kaoru; Hasegawa, Hirokazu

    2018-02-01

    We investigate an enhancement of the orientation of OCS molecules by irradiating them with a near IR (ω) ultrashort laser pulse for alignment followed by another ultrashort laser pulse for orientation, which is synthesized by a phase-locked coherent superposition of the near IR laser pulse and its second harmonic (2ω). On the basis of the asymmetry in the ejection direction of S3+ fragment ions generated by the Coulomb explosion of multiply charged OCS, we show that the extent of the orientation of OCS is significantly enhanced when the delay between the alignment pulse and the orientation pulse is a quarter or three quarters of the rotational period. The recorded enhanced orientation was interpreted well by a numerical simulation of the temporal evolution of a rotational wave packet prepared by the alignment and orientation pulses.

  8. Electric fields in plasmas under pulsed currents

    International Nuclear Information System (INIS)

    Tsigutkin, K.; Doron, R.; Stambulchik, E.; Bernshtam, V.; Maron, Y.; Fruchtman, A.; Commisso, R. J.

    2007-01-01

    Electric fields in a plasma that conducts a high-current pulse are measured as a function of time and space. The experiment is performed using a coaxial configuration, in which a current rising to 160 kA in 100 ns is conducted through a plasma that prefills the region between two coaxial electrodes. The electric field is determined using laser spectroscopy and line-shape analysis. Plasma doping allows for three-dimensional spatially resolved measurements. The measured peak magnitude and propagation velocity of the electric field is found to match those of the Hall electric field, inferred from the magnetic-field front propagation measured previously

  9. Controlling the alignment of neutral molecules by a strong laser field

    DEFF Research Database (Denmark)

    Sakai, H.; Hilligsøe, Karen Marie; Hald, K.

    1999-01-01

    by lowering the initial rotational energy of the molecules or by increasing the laser intensity. The alignment is measured by photodissociating the molecules with a femtosecond laser pulse and detecting the direction of the photofragments by imaging techniques. The strongest degree of alignment observed......A strong nonresonant nanosecond laser pulse is used to align neutral iodine molecules. The technique, applicable to both polar and nonpolar molecules, relies on the interaction between the strong laser field and the induced dipole moment of the molecules. The degree of alignment is enhanced...

  10. Auroral electron fluxes induced by static magnetic field aligned electric field and plasma wave turbulence

    International Nuclear Information System (INIS)

    Assis, A.S. de; Silva, C.E. da; Dias Tavares, A. Jr.; Leubner, C.; Kuhn, S.

    2001-07-01

    We have studied the formation of auroral electron fluxes induced by a field aligned dc electric field in the presence of plasma wave turbulence. The effect of the wave spectral shape on the production rate has been considered. This acceleration scheme was modelled by the weak turbulence approach. The electron fluxes for narrow and broad band spectra, in the case of low and high phase velocities, are calculated, and it is found as a general feature, for all modes, that their enhancement is larger the weaker the background electric field, while for its absolute enhancement it is just the opposite. The electron fluxes are enhanced by many orders of magnitude over that without turbulence. It is also shown that the modes enhance the runaway production rate via their Cherenkov dissipation, and that a synergetic effect occurs in the enhancement when more than one mode turbulent is present in the acceleration region. (author)

  11. Rotating field current drive in spherical plasmas

    International Nuclear Information System (INIS)

    Brotherton-Ratcliffe, D.; Storer, R.G.

    1988-01-01

    The technique of driving a steady Hall current in plasmas using a rotating magnetic field is studied both numerically and analytically in the approximation of negligible ion flow. A spherical plasma bounded by an insulating wall and immersed in a uniform magnetic field which has both a rotating component (for current drive) and a constant ''vertical'' component (for MHD equilibrium) is considered. The problem is formulated in terms of an expansion of field quantities in vector spherical harmonics. The numerical code SPHERE solves the resulting pseudo-harmonic equations by a multiple shooting technique. The results presented, in addition to being relevant to non-inductive current drive generally, have a direct relevance to the rotamak experiments. For the case of no applied vertical field the steady state toroidal current driven by the rotating field per unit volume of plasma is several times less than in the long cylinder limit for a plasma of the same density, resistivity and radius. The application of a vertical field, which for certain parameter regimes gives rise to a compact torus configuration, improves the current drive dramatically and in many cases gives ''better'' current drive than the long cylinder limit. This result is also predicted by a second order perturbation analysis of the pseudo-harmonic equations. A steady state toroidal field is observed which appears consistent with experimental observations in rotamaks regarding magnitude and spatial dependence. This is an advance over previous analytical theory which predicted an oppositely directed toroidal field of undefined magnitude. (author)

  12. Dispersion equations for field-aligned cyclotron waves in axisymmetric magnetospheric plasmas

    Directory of Open Access Journals (Sweden)

    N. I. Grishanov

    2006-03-01

    Full Text Available In this paper, we derive the dispersion equations for field-aligned cyclotron waves in two-dimensional (2-D magnetospheric plasmas with anisotropic temperature. Two magnetic field configurations are considered with dipole and circular magnetic field lines. The main contribution of the trapped particles to the transverse dielectric permittivity is estimated by solving the linearized Vlasov equation for their perturbed distribution functions, accounting for the cyclotron and bounce resonances, neglecting the drift effects, and assuming the weak connection of the left-hand and right-hand polarized waves. Both the bi-Maxwellian and bi-Lorentzian distribution functions are considered to model the ring current ions and electrons in the dipole magnetosphere. A numerical code has been developed to analyze the dispersion characteristics of electromagnetic ion-cyclotron waves in an electron-proton magnetospheric plasma with circular magnetic field lines, assuming that the steady-state distribution function of the energetic protons is bi-Maxwellian. As in the uniform magnetic field case, the growth rate of the proton-cyclotron instability (PCI in the 2-D magnetospheric plasmas is defined by the contribution of the energetic ions/protons to the imaginary part of the transverse permittivity elements. We demonstrate that the PCI growth rate in the 2-D axisymmetric plasmasphere can be significantly smaller than that for the straight magnetic field case with the same macroscopic bulk parameters.

  13. Eddy currents in pulsed field measurements

    International Nuclear Information System (INIS)

    Kuepferling, M.; Groessinger, R.; Wimmer, A.; Taraba, M.; Scholz, W.

    2002-01-01

    Full text: One problem of pulsed field magnetometry is an error in magnetization, which appears in measurements of conducting samples. This error is due to eddy currents induced by a time varying field. To allow predictions how eddy currents exert influence on the hysteresis loop, systematic experimental and theoretical studies of pulsed field measurements of metallic samples were performed. The theoretical studies include analytical calculations as well as numerical ones using a 2D finite element software. In the measurements three physical parameters have been varied: i) the conductivity of the sample by using two different materials, in this case technical Cu and Al ii) size and shape of the sample by using cylinders, spheres and cuboids iii) the pulse duration of the external field by changing the capacitor battery from 8mF ( =9.1ms) to 24mF ( =15.7ms). The time dependence of the external field corresponds with a pulsed damped harmonic oscillation with a maximum value of 5.2T. The samples were studied in the as cast state (after machining) as well as after heat treatment. Theoretical calculations showed not only good agreement with the absolute values of the measured eddy current m agnetization , they also gave an explanation of the shape of the eddy current hysteresis and the dependence of the eddy current 'magnetization' on parameters as pulse duration of the external field and conductivity of the sample. (author)

  14. Oscillating field current drive for reversed field pinch discharges

    International Nuclear Information System (INIS)

    Schoenberg, K.F.; Gribble, R.F.; Baker, D.A.

    1984-06-01

    Oscillating Field Current Drive (OFCD), also known as F-THETA pumping, is a steady-state current-drive technique proposed for the Reversed Field Pinch (RFP). Unlike other current-drive techniques, which employ high-technology, invasive, and power intensive schemes using radio frequency or neutral particle injection, F-THETA pumping entails driving the toroidal and poloidal magnetic field circuits with low-frequency (audio) oscillating voltage sources. Current drive by this technique is a consequence of the strong nonlinear plasma coupling in the RFP. Because of its low frequency and efficient plasma coupling, F-THETA pumping shows excellent promise as a reactor-relevant current-drive technique. A conceptual and computational study of this concept, including its experimental and reactor relevance, is explored in this paper

  15. Inertial range spectrum of field-aligned whistler turbulence

    DEFF Research Database (Denmark)

    Dwivedi, Navin Kumar; Singh, Shobhana

    2017-01-01

    the background magnetic field is exploited to derive the inertial range scaling laws corresponding to the electric field and magnetic field fluctuations. The model is based on the concept of Iroshnikov-Kraichnan inertial range magnetohydrodynamic turbulence. The present phenomenological turbulence scaling model...

  16. Field emission characteristics of vertically aligned carbon nanotubes with honeycomb configuration grown onto glass substrate with titanium coating

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yung-Jui [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chang, Hsin-Yueh; Chang, Hsuan-Chen [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Shih, Yi-Ting; Su, Wei-Jhih [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Ciou, Chen-Hong [Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Chen, Yi-Ling [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Honda, Shin-ichi [Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280 (Japan); Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China); Department of Electronic and computer Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

    2014-03-15

    Highlights: • We have successfully designed the honeycomb patterns on glass substrate by photolithography technique. • Honeycomb-VACNTs were synthesized successfully onto glass substrate by using thermal CVD and covered different Ti films on VACNTs by e-beam evaporation. • After coating the Ti films, the current density reached 7 mA/cm{sup 2} when the electric field was 2.5 V/μm. • The fluorescence of VACNTs with Ti 15 nm films exhibits the high brightness screen and emission uniformity. -- Abstract: Carbon nanotubes (CNTs) were grown successfully onto a glass substrate using thermal chemical vapor deposition (TCVD) with C{sub 2}H{sub 2} gas at 700 °C. The synthesized CNTs exhibited good crystallinity and a vertically aligned morphology. The vertically aligned CNTs (VACNTs) were patterned with a honeycomb configuration using photolithography and characterized using field emission (FE) applications. Owing to the electric field concentration, the FE current density of VACNTs with honeycomb configuration was higher than that of the un-patterned VACNTs. Ti was coated onto the VACNT surface utilizing the relatively lower work function property to enhance the FE current density. The FE current density reached up to 7.0 mA/cm{sup 2} at an applied electric field of 2.5 V/μm. A fluorescent screen was monitored to demonstrate uniform FE VACNTs with a honeycomb configuration. The designed field emitter provided an admirable example for FE applications.

  17. The use of the empirical mode decomposition for the identification of mean field aligned reference frames

    Directory of Open Access Journals (Sweden)

    Mauro Regi

    2017-01-01

    Full Text Available The magnetic field satellite data are usually referred to geocentric coordinate reference frame. Conversely, the magnetohydrodynamic waves modes in magnetized plasma depend on the ambient magnetic field, and is then useful to rotate the magnetic field measurements into the mean field aligned (MFA coordinate system. This reference frame is useful to study the ultra low frequency magnetic field variations along the direction of the mean field and perpendicularly to it. In order to identify the mean magnetic field the classical moving average (MAVG approach is usually adopted but, under particular conditions, this procedure induces undesired features, such as spectral alteration in the rotated components. We discuss these aspects promoting an alternative and more efficient method for mean field aligned projection, based on the empirical mode decomposition (EMD.

  18. Influence of contact height on the performance of vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi; Cheng, Yingchun; Guo, Zaibing; Wang, Zhihong; Zhu, Zhiyong; Zhang, Qing; Chan-Park, Chanpark; Schwingenschlö gl, Udo; Zhang, Xixiang

    2013-01-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been experimentally demonstrated (J. Li et al., Carbon, 2012, 50, 4628-4632). The source and drain contact heights in vertical CNTFETs could be much higher than in flat CNTFETs if the fabrication process is not optimized. To understand the impact of contact height on transistor performance, we use a semi-classical method to calculate the characteristics of CNTFETs with different contact heights. The results show that the drain current decreases with increasing contact height and saturates at a value governed by the thickness of the oxide. The current reduction caused by the increased contact height becomes more significant when the gate oxide is thicker. The higher the drain voltage, the larger the current reduction. It becomes even worse when the band gap of the carbon nanotube is larger. The current can differ by a factor of more than five between the CNTEFTs with low and high contact heights when the oxide thickness is 50 nm. In addition, the influence of the contact height is limited by the channel length. The contact height plays a minor role when the channel length is less than 100 nm. © 2013 The Royal Society of Chemistry.

  19. Magnetic field alignment of coil-coil diblock copolymers and blends via intrinsic chain anisotropy

    Science.gov (United States)

    Rokhlenko, Yekaterina; Majewski, Pawel; Larson, Steven; Yager, Kevin; Gopalan, Padma; Avgeropoulos, Apostolos; Chan, Edwin; Osuji, Chinedum

    Magnetic fields can control alignment of self-assembled soft materials such as block copolymers provided there is a suitably large magnetic susceptibility anisotropy present in the system. Recent results have highlighted the existence of a non-trivial intrinsic anisotropy in coil-coil diblock copolymers, specifically in lamellar-forming PS-b-P4VP, which enables alignment at field strengths of a few tesla in systems lacking mesogenic components. Alignment is predicated on correlation in the orientation of end-end vectors implied by the localization of block junctions at the microdomain interface and is observed on cooling across the order-disorder transition in the presence of the field. For appropriate combinations of field strength and grain size, we can leverage intrinsic chain anisotropy to magnetically direct self-assembly of many non-mesogenic systems, including other coil-coil BCPs like PS-b-PDMS and PS-b-PMMA, blends of BCPs of disparate morphologies and MWs, and blends of BCPs with homopolymers. This is noteworthy as blends of PS-b-P4VP with PEO provide a route to form functional materials such as nanoporous films by dissolution of PEO, or aligned ion conduction materials. We survey these various systems using TEM and in-situ X-ray scattering to study the phase behavior and temperature-, time- and field- dependent dynamics of alignment.

  20. Quantitative analysis of gold nanorod alignment after electric field assisted deposition

    NARCIS (Netherlands)

    Ahmed, W.; Ahmed, Waqqar; Kooij, Ernst S.; van Silfhout, Arend; Poelsema, Bene

    2009-01-01

    We have studied the alignment of colloidal gold nanorods, deposited from solution onto well-defined substrates in the presence of an AC electric field generated by micrometer spaced electrodes. The field strengths employed in our experiments are sufficiently large to overcome Brownian motion and

  1. Effect of upflowing field-aligned electron beams on the electron ...

    Indian Academy of Sciences (India)

    The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at the frequencies r < e, propagating downward in the direction of the Earth's magnetic field, has been analysed in the auroral region at e/e < 1 where e is the plasma frequency and e is the ...

  2. Light-field-driven currents in graphene

    Science.gov (United States)

    Higuchi, Takuya; Heide, Christian; Ullmann, Konrad; Weber, Heiko B.; Hommelhoff, Peter

    2017-10-01

    The ability to steer electrons using the strong electromagnetic field of light has opened up the possibility of controlling electron dynamics on the sub-femtosecond (less than 10-15 seconds) timescale. In dielectrics and semiconductors, various light-field-driven effects have been explored, including high-harmonic generation, sub-optical-cycle interband population transfer and the non-perturbative change of the transient polarizability. In contrast, much less is known about light-field-driven electron dynamics in narrow-bandgap systems or in conductors, in which screening due to free carriers or light absorption hinders the application of strong optical fields. Graphene is a promising platform with which to achieve light-field-driven control of electrons in a conducting material, because of its broadband and ultrafast optical response, weak screening and high damage threshold. Here we show that a current induced in monolayer graphene by two-cycle laser pulses is sensitive to the electric-field waveform, that is, to the exact shape of the optical carrier field of the pulse, which is controlled by the carrier-envelope phase, with a precision on the attosecond (10-18 seconds) timescale. Such a current, dependent on the carrier-envelope phase, shows a striking reversal of the direction of the current as a function of the driving field amplitude at about two volts per nanometre. This reversal indicates a transition of light-matter interaction from the weak-field (photon-driven) regime to the strong-field (light-field-driven) regime, where the intraband dynamics influence interband transitions. We show that in this strong-field regime the electron dynamics are governed by sub-optical-cycle Landau-Zener-Stückelberg interference, composed of coherent repeated Landau-Zener transitions on the femtosecond timescale. Furthermore, the influence of this sub-optical-cycle interference can be controlled with the laser polarization state. These coherent electron dynamics in

  3. Simultaneous measurements of HF-enhanced plasma waves and artificial field-aligned irregularities at Arecibo

    International Nuclear Information System (INIS)

    Noble, S.T.; Djuth, F.T.

    1990-01-01

    Two radar systems with beams intersecting in the HF-modified F region were used to simultaneously measure HF-enhanced plasma lines (HFPLs) and artificial geomagnetic field-aligned irregularities (AFAIs). The Arecibo 430-MHz radar was used for the HFPL observations, and a portable 49.92-MHz backscatter radar was deployed on the island of Guadeloupe to monitor the AFAIs. The experiment was desgined to examine the degree to which HF-induced plasma turbulence influences the development of AFAIs. When the HF beam is stepped up in power, sustained HFPLs and AFAIs are first observed at the same HF power level, indicating that ponderomotively driven instabilities may be involved in the early time development of AFAIs. As the HF power is increased, the HFPL backscatter power begins to saturate at ∼70 MW effective radiated power (ERP). However, the backscatter from AFAIs is linearly dependent on HF power, even at the highest (120 MW ERP) HF power levels available at Arecibo. This suggests that additional processes may contribute to the development of AFAIs. For example, ponderomotively driven instabilities may give rise to weak geomagnetic field-aligned irregularities that are subsequently driven unstable by processes excited near the upper hybrid resonance. It is also likely that AFAIs greatly impact the development of HF-induced plasma turbulence at late times (>1 s) following HF turn-on. Once the ionosphere is preconditioned by high-power HF modifications, AFAIs and HFPLs can be simultaneously sustained at a much lower HF power level than that needed to originally excite them. The nature of the preconditioning process is currently not well understood. New theoretical initiatives are clearly needed to guide future experimental activity in this area

  4. Field emission current from a junction field-effect transistor

    International Nuclear Information System (INIS)

    Monshipouri, Mahta; Abdi, Yaser

    2015-01-01

    Fabrication of a titanium dioxide/carbon nanotube (TiO 2 /CNT)-based transistor is reported. The transistor can be considered as a combination of a field emission transistor and a junction field-effect transistor. Using direct current plasma-enhanced chemical vapor deposition (DC-PECVD) technique, CNTs were grown on a p-typed (100)-oriented silicon substrate. The CNTs were then covered by TiO 2 nanoparticles 2–5 nm in size, using an atmospheric pressure CVD technique. In this device, TiO 2 /CNT junction is responsible for controlling the emission current. High on/off-current ratio and proper gate control are the most important advantages of device. A model based on Fowler–Nordheim equation is utilized for calculation of the emission current and the results are compared with experimental data. The effect of TiO 2 /CNT hetero-structure is also investigated, and well modeled

  5. Spin alignment of ρ0 mesons produced in antineutrino and neutrino neon charged-current interactions

    Science.gov (United States)

    Wittek, W.; Guy, J.; Adeholz, M.; Allport, P.; Baton, J. P.; Berggren, M.; Bertrand, D.; Brisson, V.; Bullock, F. W.; Burkot, W.; Calicchio, M.; Clayton, E. F.; Coghen, T.; Cooper-Sarkar, A. M.; Erriquez, O.; Fitch, P. J.; Fogli-Muciaccia, M. T.; Hulth, P. O.; Jones, G. T.; Kasper, P.; Klein, H.; Marage, P.; Middleton, R. P.; Miller, D. B.; Mobayyen, M. M.; Morrison, D. R. O.; Neveu, M.; O'Neale, S. W.; Parker, M. A.; Petiau, P.; Sacton, J.; Sansum, R. A.; Schmitz, N.; Simopoulou, E.; Vallee, C.; Varvell, K.; Vayaki, A.; Venus, W.; Wachsmuth, H.; Wells, J.

    1987-03-01

    In a bubble chamber experiment with BEBC the spin alignment parameter η=1/2 (2ϱ00 - ϱ11 - ϱ-1-1) is measured for ϱ0 mesons produced in deep inelastic charged-current antineutrino and neutrono interactions on neon. In the current fragmentation region η is found to be ηv=0.48+/-0.27 (stat.)+/-0.15 (syst.) for vNe and ηv=0.12+/-0.20 (stat.)+/-0.10 (syst.) for vNe interactions Present address: University College London, London WC1E 6BT, UK.

  6. Spin alignment of ρ0 mesons produced in antineutrino and neutrino neon charged-current interactions

    International Nuclear Information System (INIS)

    Wittek, W.; Aderholz, M.; Schmitz, N.; Guy, J.; Cooper-Sarkar, A.M.; Venus, W.; Brisson, V.; Petiau, P.; Vallee, C.; Calicchio, M.; Erriquez, O.; Fogli-Muciaccia, M.T.; Jones, G.T.; Middleton, R.P.; O'Neale, S.W.; Varvell, K.; Klein, H.; Morrison, D.R.O.; Parker, M.A.; Wachsmuth, H.; Vayaki, A.

    1987-01-01

    In a bubble chamber experiment with BEBC the spin alignment parameter η=1/2(2ρ 00 -ρ 11 -ρ -1-1 ) is measured for ρ 0 mesons produced in deep inelastic charged-current antineutrino and neutrino interactions on neon. In the current fragmentation region η is found to be η ν =0.48±0.27(stat.)±0.15(syst.) for anti νNe and η ν =0.12±0.20(stat.)±0.10(syst.) for νNe interactions. (orig.)

  7. Automatic alignment device for focal spot measurements in the center of the field for mammography

    International Nuclear Information System (INIS)

    Vieira, Marcelo A.C.; Watanabe, Alex O.; Oliveira Junior, Paulo D.; Schiabel, Homero

    2010-01-01

    Some quality control procedures used for mammography, such as focal spot evaluation, requires previous alignment of the measurement equipment with the X-ray central beam. However, alignment procedures are, in general, the most difficult task and the one that needs more time to be performed. Moreover, the operator sometimes is exposed to radiation during this procedure. This work presents an automatic alignment system for mammographic equipment that allows locating the central ray of the radiation beam and, immediately, aligns with it by dislocating itself automatically along the field. The system consists on a bidirectional moving device, connected to a CCD sensor for digital radiographic image acquisition. A computational analysis of a radiographic image, acquired at any position on the field, is performed in order to determine its positioning under the X-ray beam. Finally, a mechanical system for two moving directions, electronically controlled by a microcontroller under USB communication, makes the system to align automatically with the radiation beam central ray. The alignment process is fully automatic, fast and accurate, with no operator exposure to radiation, which allows a considerable time saving for quality control procedures achievement for mammography. (author)

  8. Adiabatic Field-Free Alignment of Asymmetric Top Molecules with an Optical Centrifuge.

    Science.gov (United States)

    Korobenko, A; Milner, V

    2016-05-06

    We use an optical centrifuge to align asymmetric top SO_{2} molecules by adiabatically spinning their most polarizable O-O axis. The effective centrifugal potential in the rotating frame confines the sulfur atoms to the plane of the laser-induced rotation, leading to the planar molecular alignment that persists after the molecules are released from the centrifuge. The periodic appearance of the full three-dimensional alignment, typically observed only with linear and symmetric top molecules, is also detected. Together with strong in-plane centrifugal forces, which bend the molecules by up to 10 deg, permanent field-free alignment offers new ways of controlling molecules with laser light.

  9. High-performance supercapacitors using a nanoporous current collector made from super-aligned carbon nanotubes

    Science.gov (United States)

    Zhou, Ruifeng; Meng, Chuizhou; Zhu, Feng; Li, Qunqing; Liu, Changhong; Fan, Shoushan; Jiang, Kaili

    2010-08-01

    Nanoporous current collectors for supercapacitors have been fabricated by cross-stacking super-aligned carbon nanotube (SACNT) films as a replacement for heavy conventional metallic current collectors. The CNT-film current collectors have good conductivity, extremely low density (27 µg cm - 2), high specific surface area, excellent flexibility and good electrochemical stability. Nanosized active materials such as NiO, Co3O4 or Mn2O3 nanoparticles can be directly synthesized on the SACNT films by a straightforward one-step, in situ decomposition strategy that is both efficient and environmentally friendly. These composite films can be integrated into a pseudo-capacitor that does not use metallic current collectors, but nevertheless shows very good performance, including high specific capacitance (~500 F g - 1, including the current collector mass), reliable electrochemical stability (<4.5% degradation in 2500 cycles) and a very high rate capability (245 F g - 1 at 155 A g - 1).

  10. Molecular alignment and orientation in short pulse laser fields

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm

    1999-01-01

    An analytical expression for the propagator associated with impulsive excitation is derived based on the Magnus expansion. We apply this expression to the excitation of angular motion out of a rotational eigenstate for a linear polar molecule in a plane polarized electromagnetic field. We show...

  11. Target aligned heliostat field layout for non-flat terrrain

    CSIR Research Space (South Africa)

    Buck, R

    2012-05-01

    Full Text Available The layout for a solar tower test facility for CSIR, Pretoria, is described. The solar tower system is designed for 400kWth receiver outlet power. The heliostat field layout takes into account both the real (non-flat) topography of the terrain...

  12. GRAIN ALIGNMENT INDUCED BY RADIATIVE TORQUES: EFFECTS OF INTERNAL RELAXATION OF ENERGY AND COMPLEX RADIATION FIELD

    International Nuclear Information System (INIS)

    Hoang, Thiem; Lazarian, A.

    2009-01-01

    Earlier studies of grain alignment dealt mostly with interstellar grains that have strong internal relaxation of energy which aligns the grain axis of maximum moment of inertia (the axis of major inertia) with respect to the grain's angular momentum. In this paper, we study the alignment by radiative torques for large irregular grains, e.g., grains in accretion disks, for which internal relaxation is subdominant. We use both numerical calculations and the analytical model of a helical grain introduced by us earlier. We demonstrate that grains in such a regime exhibit more complex dynamics. In particular, if initially the grain axis of major inertia makes a small angle with angular momentum, then radiative torques can align the grain axis of major inertia with angular momentum, and both the axis of major inertia and angular momentum are aligned with the magnetic field when attractors with high angular momentum (high-J attractors) are available. For alignment without high-J attractors, beside the earlier studied attractors with low angular momentum (low-J attractors), there appear new low-J attractors. In addition, we also study the alignment of grains in the presence of strong internal relaxation, but induced not by a radiation beam as in earlier studies but instead induced by a complex radiation field that can be decomposed into dipole and quadrupole components. We found that in this situation the parameter space q max , for which high-J attractors exist in trajectory maps, is more extended, resulting in the higher degree of polarization expected. Our results are useful for modeling polarization arising from aligned dust grains in molecular clouds.

  13. The Auroral Field-aligned Acceleration - Cluster Results

    Science.gov (United States)

    Vaivads, A.; Cluster Auroral Team

    The four Cluster satellites cross the auroral field lines at altitudes well above most of acceleration region. Thus, the orbit is appropriate for studies of the generator side of this region. We consider the energy transport towards the acceleration region and different mechanisms for generating the potential drop. Using data from Cluster we can also for the first time study the dynamics of the generator on a minute scale. We present data from a few auroral field crossings where Cluster are in conjunction with DMSP satellites. We use electric and magnetic field data to estimate electrostatic po- tential along the satellite orbit, Poynting flux as well as the presence of plasma waves. These we can compare with data from particle and wave instruments on Cluster and on low latitude satellites to try to make a consistent picture of the acceleration region formation in these cases. Preliminary results show close agreement both between in- tegrated potential values at Cluster and electron peak energies at DMSP as well as close agreement between the integrated Poynting flux values at Cluster and the elec- tron energy flux at DMSP. At the end we draw a parallels between auroral electron acceleration and electron acceleration at the magnetopause.

  14. Thermal electron acceleration by electric field spikes in the outer radiation belt: generation of field-aligned pitch angle distributions

    Science.gov (United States)

    Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

    2015-12-01

    Van Allen Probes observations in the outer radiation belt have demonstrated an abundance non-linear electrostatic stucture called Time Domain Structures (TDS). One of the type of TDS is electrostatic electron-acoustic double layers (DL). Observed DLs are frequently accompanied by field-aligned (bi-directional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV (rarely up to tens of keV). We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e. due to reflections from DL potential humps. Due to this interaction some fraction of electrons is scattered into the loss cone. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher energy electrons.

  15. Current and field distribution in high temperature superconductors

    International Nuclear Information System (INIS)

    Johnston, M.D.

    1998-01-01

    The manufacture of wires from HTS materials containing copper-oxide planes is difficult because their physical and electrical properties are highly anisotropic. The electrical connectivity depends on the nearest-neighbour grain alignment and although a high degree of grain texture is achieved through processing, the tape microstructure is generally far from uniform, with weak links and porosity also complicating the picture. In order to optimise the processing, the microstructural features common to good tapes must be identified, requiring knowledge of the local properties. The preferential path taken by transport current is determined by the properties of the local microstructure and as such can be used to measure the variation in quality across the tape cross-section. By measuring the self-field profile generated by a current-carrying tape, it is possible to extract the associated current distribution. I have designed and built a Scanning Hall Probe Microscope to measure the normal field distribution above superconductor tapes carrying DC currents, operating at liquid nitrogen temperature and zero applied magnetic field. It has a spatial resolution of 50*50 μm and a field sensitivity of 5 μT, and can scan over a distance of 6 mm. The current extraction is performed by means of a deconvolution procedure based on Legendre functions. This allows a nondestructive, non-invasive method of evaluating the effects of the processing on the tapes - especially when correlated with transport and magnetisation measurement data. Conductors fabricated from Bi 2 Sr 2 Ca 2 Cu 3 O 10 , Bi 2 Sr 2 CaCu 2 O 8 and (Tl 0.78 Bi 0.22 )(Sr 0.8 Ba 0.2 ) 2 Ca 2 Cu 3 O x , have been investigated. I have confirmed the reports that in Bi-2223/Ag mono-core conductors produced by the oxide-powder-in-tube (OPIT) technique, the current flows predominantly at the edges of the tape, where the grains are long and well-aligned. This is in contrast to Bi-2212 ribbons, where the better microstructure

  16. Examining the Electric Fields of the Evening Equatorial Ionosphere When the Solar Terminator is Aligned and Not Aligned with the Magnetic Meridian

    Science.gov (United States)

    Eccles, J. V.

    2014-12-01

    The electric field structure of the equatorial ionosphere near sunset has implications on the development of plasma irregularities. The details of the development of the electric fields are examined using a global ionosphere-electrodynamics model. The results of simulations of simplified conditions show the influence of the arrangement of the solar terminator with the magnetic meridian. The relationships of the Curl-Free mechanism, the Hall Current Divergence mechanism, and the role of the Equatorial Electorjet region control the magnitude and timing of the Prereversal Enhancement of the zonal electric field as well as its altitude profile above the F region bottomside. Realistic conditions for 'equinox' and 'solstice' solar terminator arrangments are presented. The stability of the low-latitude ionosphere has a demonstrated relationship with the solar terminator alignment [Tsunoda, JGR, 1981]. The profile of the vertical and zonal electric field below the bottomside is then examined using the global model to explore the controlling elements of the electric field structure and the growth rates of the Rayleigh-Taylor instability and Collisional Shear instability.Tsunoda, R. T. (1985), Control of the seasonal and longitudinal occurrence of equatorial scintillations by the longitudinal gradient in integrated E region Pedersen conductivity, J. Geophys. Res., 90(A1),447-456, doi:10.1029/JA090iA01p00447.

  17. Observation of enhanced field-free molecular alignment by two laser pulses

    DEFF Research Database (Denmark)

    Bisgaard, Christer; Poulsen, Mikael Dahlerup; Peronne, Emmanuel

    2004-01-01

    We show experimentally that field-free alignment of iodobenzene molecules, induced by a single, intense, linearly polarized 1.4-ps-long laser pulse, can be strongly enhanced by dividing the pulse into two optimally synchronized pulses of the same duration. For a given total energy of the two...

  18. Theory of strong-field ionization of aligned CO2

    DEFF Research Database (Denmark)

    Abu-Samha, Mahmoud; Madsen, Lars Bojer

    2009-01-01

    resonance states, and the alignment-dependent ionization yields do not follow the electron density of the initial states. The theory explains the breakdown of semianalytical theories, such as the molecular tunneling theory and strong-field approximation, where excited electronic structure is neglected....

  19. Magnetic-field-aligned characteristics of plasma bubbles in the nighttime equatorial ionosphere

    International Nuclear Information System (INIS)

    Tsunoda, R.T.

    1980-01-01

    Measurements of both incoherent-scatter (IS) and backscatter from field-aligned irregularities (FAI) were made in 1978 with ALTAIR, a fully-steerable high-power radar, to investigate the magnetic-field-aligned characteristics of equatorial plasma bubbles. By operating the radar in a latitude-scan IS mode it was possible to map the location and percentage depletion of plasma bubbles as a function of altitude. By showing that backscatter from FAI is spatially collocated with the upper wall of plasma bubbles it was possible to use the spatial displacement of a field aligned backscatter region to estimate the upward bubble velocity. Besides showing that plasma bubbles are indeed aligned along magnetic field lines, this data set is used to show that a plasma bubble with a percentage depletion of as much as 90% does not have as large an upward velocity as predicted by two-dimensional models. Instead, the inferred bubble velocity is shown to be in better agreement with the bubble velocity predicted by theoretical models using flux-integrated values of electron density and Pedersen conductivity. The need to use flux-tube-integrated values when comparing theory and observation is further stressed by the presence of a non-uniform latitudinal distribution of electron density (i.e. the equatorial anomaly) that was found in the latitude-scan data. (author)

  20. Relaxing the electrostatic screening effect by patterning vertically-aligned silicon nanowire arrays into bundles for field emission application

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Yung-Jr, E-mail: yungjrhung@gmail.com [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Department of Photonics, National Sun Yat-sen University, No. 70, Lienhai Rd., Kaohsiung 80424, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Lee, San-Liang [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Beng, Looi Choon [Faculty of Engineering, Multimedia University, Jalan Multimedia, 63100 Cyberjaya, Selangor (Malaysia); Chang, Hsuan-Chen [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Huang, Yung-Jui [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Lee, Kuei-Yi; Huang, Ying-Sheng [Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China); Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan, ROC (China)

    2014-04-01

    Top-down fabrication strategies are proposed and demonstrated to realize arrays of vertically-aligned silicon nanowire bundles and bundle arrays of carbon nanotube–silicon nanowire (CNT–SiNW) heterojunctions, aiming for releasing the electrostatic screening effect and improving the field emission characteristics. The trade-off between the reduction in the electrostatic screening effect and the decrease of emission sites leads to an optimal SiNW bundle arrangement which enables the lowest turn-on electric field of 1.4 V/μm and highest emission current density of 191 μA/cm{sup 2} among all testing SiNW samples. Benefiting from the superior thermal and electrical properties of CNTs and the flexible patterning technologies available for SiNWs, bundle arrays of CNT–SiNW heterojunctions show improved and highly-uniform field emission with a lower turn-on electric field of 0.9 V/μm and higher emission current density of 5.86 mA/cm{sup 2}. The application of these materials and their corresponding fabrication approaches is not limited to the field emission but can be used for a variety of emerging fields like nanoelectronics, lithium-ion batteries, and solar cells. - Highlights: • Aligned silicon nanowire (SiNW) bundle arrays are realized with top-down methods. • Growing carbon nanotubes atop SiNW bundle arrays enable uniform field emission. • A turn-on field of 0.9 V/μm and an emission current of > 5 mA/cm{sup 2} are achieved.

  1. Low temperature superconductor and aligned high temperature superconductor magnetic dipole system and method for producing high magnetic fields

    Science.gov (United States)

    Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.; Weggel, Robert J.; Palmer, Robert; Anerella, Michael D.; Schmalzle, Jesse

    2017-10-17

    A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of the large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.

  2. Field emission current from a junction field-effect transistor

    Energy Technology Data Exchange (ETDEWEB)

    Monshipouri, Mahta; Abdi, Yaser, E-mail: y.abdi@ut.ac.ir [University of Tehran, Nano-Physics Research Laboratory, Department of Physics (Iran, Islamic Republic of)

    2015-04-15

    Fabrication of a titanium dioxide/carbon nanotube (TiO{sub 2}/CNT)-based transistor is reported. The transistor can be considered as a combination of a field emission transistor and a junction field-effect transistor. Using direct current plasma-enhanced chemical vapor deposition (DC-PECVD) technique, CNTs were grown on a p-typed (100)-oriented silicon substrate. The CNTs were then covered by TiO{sub 2} nanoparticles 2–5 nm in size, using an atmospheric pressure CVD technique. In this device, TiO{sub 2}/CNT junction is responsible for controlling the emission current. High on/off-current ratio and proper gate control are the most important advantages of device. A model based on Fowler–Nordheim equation is utilized for calculation of the emission current and the results are compared with experimental data. The effect of TiO{sub 2}/CNT hetero-structure is also investigated, and well modeled.

  3. Effect of upflowing field-aligned electron beams on the electron ...

    Indian Academy of Sciences (India)

    Abstract. The role of low density upflowing field-aligned electron beams (FEBs) on the growth rate of the electron cyclotron waves at the frequencies ωr < Ωe, propagating downward in the direction of the Earth's magnetic field, has been analysed in the auroral region at ωe/Ωe < 1 where ωe is the plasma frequency and Ωe is ...

  4. Current distribution and ac susceptibility response of a thin superconducting disc in an axial field: a theoretical approach

    Science.gov (United States)

    Aruna, S. A.; Zhang, P.; Lin, F. Y.; Ding, S. Y.; Yao, X. X.

    2000-04-01

    Within the framework of the thermally activated process of the flux line or flux line bundles, and by time integration of the 1D equation of motion of the circulating current density icons/Journals/Common/vecJ" ALT="vecJ" ALIGN="TOP"/> (icons/Journals/Common/rho" ALT="rho" ALIGN="TOP"/> ,t ), which is suitable for thin superconducting films (R >>d ,icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> icons/Journals/Common/lambda" ALT="lambda" ALIGN="TOP"/> ), we present numerical calculations of the current profiles, magnetization hysteresis loops and ac susceptibility icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> n = icons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> ´n +iicons/Journals/Common/chi" ALT="chi" ALIGN="TOP"/> ´´n for n = 1, 3 and 5 of a thin disc immersed in an axial time-dependent external magnetic field Ba (t ) = Bdc +Bac cos(2icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/> icons/Journals/Common/nu" ALT="nu" ALIGN="TOP"/> t ). Our calculated results are compared with those of the critical state model (CSM) and found to prove the approximate validity of the CSM below the irreversibility field. The differences between our computed results and those of the CSM are also discussed.

  5. A fast alignment method for breast MRI follow-up studies using automated breast segmentation and current-prior registration

    Science.gov (United States)

    Wang, Lei; Strehlow, Jan; Rühaak, Jan; Weiler, Florian; Diez, Yago; Gubern-Merida, Albert; Diekmann, Susanne; Laue, Hendrik; Hahn, Horst K.

    2015-03-01

    In breast cancer screening for high-risk women, follow-up magnetic resonance images (MRI) are acquired with a time interval ranging from several months up to a few years. Prior MRI studies may provide additional clinical value when examining the current one and thus have the potential to increase sensitivity and specificity of screening. To build a spatial correlation between suspicious findings in both current and prior studies, a reliable alignment method between follow-up studies is desirable. However, long time interval, different scanners and imaging protocols, and varying breast compression can result in a large deformation, which challenges the registration process. In this work, we present a fast and robust spatial alignment framework, which combines automated breast segmentation and current-prior registration techniques in a multi-level fashion. First, fully automatic breast segmentation is applied to extract the breast masks that are used to obtain an initial affine transform. Then, a non-rigid registration algorithm using normalized gradient fields as similarity measure together with curvature regularization is applied. A total of 29 subjects and 58 breast MR images were collected for performance assessment. To evaluate the global registration accuracy, the volume overlap and boundary surface distance metrics are calculated, resulting in an average Dice Similarity Coefficient (DSC) of 0.96 and root mean square distance (RMSD) of 1.64 mm. In addition, to measure local registration accuracy, for each subject a radiologist annotated 10 pairs of markers in the current and prior studies representing corresponding anatomical locations. The average distance error of marker pairs dropped from 67.37 mm to 10.86 mm after applying registration.

  6. Controlling the diameters and field emission properties of vertically aligned carbon nanotubes synthesized by thermal chemical vapor deposition

    International Nuclear Information System (INIS)

    Choi, Sung Yool; Kang, Young Il; Cho, Kyoung Ik; Choi, Kyu Seok; Kim, Do Jin

    2001-01-01

    We report here the synthesis of vertically well-aligned carbon nanotubes and the effect of catalytic metal layer on the diameter of grown carbon nanotubes and the field emission characteristics of them, The carbon nanotubes were grown by thermal chemical vapor deposition at temperatures below 900 .deg. C on Fe metal catalytic layer, deposited by sputtering process on a Si substrate and pretreated by heat and NH 3 gas. We found that the thickness of metal layers could be an important parameter in controlling the diameters of carbon nanotubes. With varying the thickness of the metal layers the grain sizes of them also vary so that the diameters of the nanotubes could be controlled. Field emission measurement has been made on the carbon nanotube field emitters at room temperature in a vacuum chamber below 10 -6 Torr. Our vertically aligned carbon nanotube field emitter of the smallest diameter emits a current density about 10 mA/cm 2 at 7.2 V/μm. The field emission property of the carbon nanotubes shows strong dependence on the nanotube diameters as expected

  7. Field-aligned plasma-potential structure formed by local electron cyclotron resonance

    International Nuclear Information System (INIS)

    Hatakeyama, Rikizo; Kaneko, Toshiro; Sato, Noriyoshi

    2001-01-01

    The significance of basic experiments on field-aligned plasma-potential structure formed by local electron cyclotron resonance (ECR) is claimed based on the historical development of the investigation on electric double layer and electrostatic potential confinement of open-ended fusion-oriented plasmas. In the presence of a single ECR point in simple mirror-type configurations of magnetic field, a potential dip (thermal barrier) appears around this point, being followed by a subsequent potential hump (plug potential) along a collisionless plasma flow. The observed phenomenon gives a clear-cut physics to the formation of field-aligned plug potential with thermal barrier, which is closely related to the double layer formation triggered by a negative dip. (author)

  8. Scattering of field-aligned beam ions upstream of Earth's bow shock

    Directory of Open Access Journals (Sweden)

    A. Kis

    2007-03-01

    Full Text Available Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.

  9. Scattering of field-aligned beam ions upstream of Earth's bow shock

    Directory of Open Access Journals (Sweden)

    A. Kis

    2007-03-01

    Full Text Available Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.

  10. Positioning and aligning CNTs by external magnetic field to assist localised epoxy cure

    Directory of Open Access Journals (Sweden)

    Ariu G.

    2016-01-01

    Full Text Available This work focuses on the generation of conductive networks through the localised alignment of nano fillers, such as multi-walled carbon nanotubes (MWCNTs. The feasibility of alignment and positioning of functionalised MWCNTs by external DC magnetic fields was investigated. The aim of this manipulation is to enhance resin curing through AC induction heating due to hysteresis losses from the nanotubes. Experimental analyses focused on in-depth assessment of the nanotube functionalisation, processing and characterisation of magnetic, rheological and cure kinetics properties of the MWCNT solution. The study has shown that an external magnetic field has great potential for positioning and alignment of CNTs. The study demonstrated potential for creating well-ordered architectures with an unprecedented level of control of network geometry. Magnetic characterisation indicated cobalt-plated nanotubes to be the most suitable candidate for magnetic alignment due to their high magnetic sensitivity. Epoxy/metal-plated CNT nanocomposite systems were validated by thermal analysis as induction heating mediums. The curing process could therefore be optimised by the use of dielectric resins. This study offers a first step towards the proof of concept of this technique as a novel repair technology.

  11. Positioning and aligning CNTs by external magnetic field to assist localised epoxy cure

    Science.gov (United States)

    Ariu, G.; Hamerton, I.; Ivanov, D.

    2016-01-01

    This work focuses on the generation of conductive networks through the localised alignment of nano fillers, such as multi-walled carbon nanotubes (MWCNTs). The feasibility of alignment and positioning of functionalised MWCNTs by external DC magnetic fields was investigated. The aim of this manipulation is to enhance resin curing through AC induction heating due to hysteresis losses from the nanotubes. Experimental analyses focused on in-depth assessment of the nanotube functionalisation, processing and characterisation of magnetic, rheological and cure kinetics properties of the MWCNT solution. The study has shown that an external magnetic field has great potential for positioning and alignment of CNTs. The study demonstrated potential for creating well-ordered architectures with an unprecedented level of control of network geometry. Magnetic characterisation indicated cobalt-plated nanotubes to be the most suitable candidate for magnetic alignment due to their high magnetic sensitivity. Epoxy/metal-plated CNT nanocomposite systems were validated by thermal analysis as induction heating mediums. The curing process could therefore be optimised by the use of dielectric resins. This study offers a first step towards the proof of concept of this technique as a novel repair technology.

  12. High-performance supercapacitors using a nanoporous current collector made from super-aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Ruifeng; Meng Chuizhou; Zhu Feng; Li Qunqing; Liu Changhong; Fan Shoushan; Jiang Kaili, E-mail: JiangKL@tsinghua.edu.cn [Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084 (China)

    2010-08-27

    Nanoporous current collectors for supercapacitors have been fabricated by cross-stacking super-aligned carbon nanotube (SACNT) films as a replacement for heavy conventional metallic current collectors. The CNT-film current collectors have good conductivity, extremely low density (27 {mu}g cm{sup -2}), high specific surface area, excellent flexibility and good electrochemical stability. Nanosized active materials such as NiO, Co{sub 3}O{sub 4} or Mn{sub 2}O{sub 3} nanoparticles can be directly synthesized on the SACNT films by a straightforward one-step, in situ decomposition strategy that is both efficient and environmentally friendly. These composite films can be integrated into a pseudo-capacitor that does not use metallic current collectors, but nevertheless shows very good performance, including high specific capacitance ({approx}500 F g{sup -1}, including the current collector mass), reliable electrochemical stability (<4.5% degradation in 2500 cycles) and a very high rate capability (245 F g{sup -1} at 155 A g{sup -1}).

  13. Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

    Energy Technology Data Exchange (ETDEWEB)

    Perkins, R. J.; Bell, R. E.; Bertelli, N.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; LeBlanc, B. P.; Kramer, G. J.; Maingi, R.; Phillips, C. K.; Podestà, M.; Roquemore, L.; Scotti, F.; Taylor, G.; Wilson, J. R. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Ahn, J-W.; Gray, T. K.; Green, D. L.; McLean, A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); and others

    2014-02-12

    Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict

  14. Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

    International Nuclear Information System (INIS)

    Perkins, R. J.; Bell, R. E.; Bertelli, N.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; LeBlanc, B. P.; Kramer, G. J.; Maingi, R.; Phillips, C. K.; Podestà, M.; Roquemore, L.; Scotti, F.; Taylor, G.; Wilson, J. R.; Ahn, J-W.; Gray, T. K.; Green, D. L.; McLean, A.

    2014-01-01

    Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict

  15. Oxygen plasma assisted end-opening and field emission enhancement in vertically aligned multiwall carbon nanotubes

    International Nuclear Information System (INIS)

    Mathur, A.; Roy, S.S.; Hazra, K.S.; Wadhwa, S.; Ray, S.C.; Mitra, S.K.; Misra, D.S.; McLaughlin, J.A.

    2012-01-01

    Highlights: ► We showed Ar/O 2 plasma can be effective for the end opening of aligned CNTs. ► The field emission property was dramatically enhanced after plasma modification. ► Microstructures were clearly understood by Raman and SEM analysis. ► Surface wet-ability at various functionalised conditions was studied. - Abstract: This paper highlights the changes in micro-structural and field emission properties of vertically aligned carbon nanotubes (VACNTs) via oxygen plasma treatment. We find that exposure of very low power oxygen plasma (6 W) at 13.56 MHz for 15–20 min, opens the tip of vertically aligned CNTs. Scanning electron microscopy and transmission electron microscopy images were used to identify the quality and micro-structural changes of the nanotube morphology and surfaces. Raman spectra showed that the numbers of defects were increased throughout the oxygen plasma treatment process. In addition, the hydrophobic nature of the VACNTs is altered significantly and the contact angle decreases drastically from 110° to 40°. It was observed that the electron field emission (EFE) characteristics are significantly enhanced. The turn-on electric field (ETOE) of CNTs decreased from ∼0.80 V μm −1 (untreated) to ∼0.60 V μm −1 (oxygen treated). We believe that the open ended VACNTs would be immensely valuable for applications such as micro/nanofluidic based filtering elements and display devices.

  16. Short-term magnetic field alignment variations of equatorial ionospheric irregularities

    International Nuclear Information System (INIS)

    Johnson, A.L.

    1988-01-01

    The ionospheric irregularities that cause equatorial scintillation are elongated along the north-south magnetic field lines. During a 1981 field campaign at Ascension Island, 250-MHz receivers were spaced from 300 m to 1.6 km along the field lines, and the signals received from the Marisat satellite were cross correlated. Data collected during eight nights of fading showed a linear relationship between fading rate and cross correlation. The alignment of the antennas was adjusted to give a zero time lag between the widely spaced receivers with a measurement accuracy of 0.03 s. Since the average irregularity velocity was 125 m/s, this time accuracy translated to an angular measurement accuracy of 0.1 deg. During a 4-hour period of nightly fading, occasional differences in time of arrival were noted that corresponded to a tilt in the north-south alignment of + or - 1 deg. Data from several nights of fading were analyzed, and each night exhibited the same variance in the north-south irregularity alignment. It is postulated that the shift in the measured peak correlation may have been caused by patches of irregularities at different altitudes where the magnetic field lines have a slightly different direction. 13 references

  17. Design and fabrication of advanced fiber alignment structures for field-installable fiber connectors

    Science.gov (United States)

    Van Erps, Jürgen; Vervaeke, Michael; Sánchez Martínez, Alberto; Beri, Stefano; Debaes, Christof; Watté, Jan; Thienpont, Hugo

    2012-06-01

    Fiber-To-The-Home (FTTH) networks have been adopted as a potential replacement of traditional electrical connections for the 'last mile' transmission of information at bandwidths over 1Gb/s. However, the success and adoption of optical access networks critically depend on the quality and reliability of connections between optical fibers. In particular a further reduction of insertion loss of field-installable connectors must be achieved without a significant increase in component cost. This requires precise alignment of fibers that can differ in terms of ellipticity, eccentricity or diameter and seems hardly achievable using today's widespread ferrule-based alignment systems. Novel low-cost structures for bare fiber alignment with outstanding positioning accuracies are strongly desired as they would allow reducing loss beyond the level achievable with ferrule-bore systems. However, the realization of such alignment system is challenging as it should provide sufficient force to position the fiber with sub-micron accuracy required in positioning the fiber. In this contribution we propose, design and prototype a bare-fiber alignment system which makes use of deflectable/compressible micro-cantilevers. Such cantilevers behave as springs and provide self-centering functionality to the structure. Simulations of the mechanical properties of the cantilevers are carried out in order to get an analytical approximation and a mathematical model of the spring constant and stress in the structure. Elastic constants of the order of 104 to 105N/m are found out to be compatible with a proof stress of 70 MPa. Finally a first self-centering structure is prototyped in PMMA using our Deep Proton Writing technology. The spring constants of the fabricated cantilevers are in the range of 4 to 6 × 104N/m and the stress is in the range 10 to 20 MPa. These self-centering structures have the potential to become the basic building blocks for a new generation of field-installable connectors.

  18. Self-field ac losses in biaxially aligned Y endash Ba endash Cu endash O tape conductors

    International Nuclear Information System (INIS)

    Iijima, Y.; Hosaka, M.; Sadakata, N.; Saitoh, T.; Kohno, O.; Takeda, K.

    1997-01-01

    Self-field ac losses were measured by the conventional ac four-probe method in biaxially aligned Y endash Ba endash Cu endash O tapes using polycrystalline Hastelloy tapes with textured yttria-stabilized-zirconia buffer layers. The ac losses increased in proportion to the fourth power of transport current in the high J c sample, and agreed well with Norris close-quote equation for thin strip conductors. However, the low J c sample had rather higher losses than Norris close-quote prediction, suggesting excessive magnetic flux penetration caused by percolated current paths. The results confirmed Norris close-quote prediction of the low ac losses for thin strip conductors, and indicated the importance of removing percolated structures of current paths to avoid higher ac losses than the theoretical predictions based on uniform conductors. copyright 1997 American Institute of Physics

  19. Self-consistent mean field forces in turbulent plasmas: Current and momentum relaxation

    International Nuclear Information System (INIS)

    Hegna, C.C.

    1997-08-01

    The properties of turbulent plasmas are described using the two-fluid equations. Under some modest assumptions, global constraints for the turbulent mean field forces that act on the ion and electron fluids are derived. These constraints imply a functional form for the parallel mean field forces in the Ohm's law and the momentum balance equation. These forms suggest that the fluctuations attempt to relax the plasma to a state where both the current and the bulk plasma momentum are aligned along the mean magnetic field with proportionality constants that are global constants. Observations of flow profile evolution during discrete dynamo activity in reversed field pinch experiments are interpreted

  20. Thermal Analysis of NR Composite with MWCNTs Aligned in a Magnetic Field

    Directory of Open Access Journals (Sweden)

    Jin Xu

    2015-01-01

    Full Text Available We got the aligned carbon tube in the rubber matrix through magnetic field. TEM shows that Fe3O4 is symmetrically coated on the outer surface of MWCNTs. Diffraction peaks corresponding to Fe3O4 cubic crystal also appeared in the X-ray diffraction spectra. Thermal conductivity of composites increases by filling the appropriate content of carbon tube. If the magnetic field is larger and the direction time is longer, a greater thermal conductivity of composites can be obtained.

  1. Beam-Based Alignment of Magnetic Field in the Fermilab Electron Cooler Cooling Section

    International Nuclear Information System (INIS)

    Seletskiy, S. M.; Tupikov, V.

    2006-01-01

    The Fermilab Electron Cooling Project requires low effective anglular spread of electrons in the cooling section. One of the main components of the effective electron angles is an angle of electron beam centroid with respect to antiproton beam. This angle is caused by the poor quality of magnetic field in the 20 m long cooling section solenoid and by the mismatch of the beam centroid to the entrance of the cooling section. This paper focuses on the beam-based procedure of the alignment of the cooling section field and beam centroid matching. The discussed procedure allows to suppress the beam centroid angles below the critical value of 0.1 mrad

  2. Multiorbital effects in strong-field ionization and dissociation of aligned polar molecules CH3I and CH3Br

    Science.gov (United States)

    Luo, Sizuo; Zhou, Shushan; Hu, Wenhui; Li, Xiaokai; Ma, Pan; Yu, Jiaqi; Zhu, Ruihan; Wang, Chuncheng; Liu, Fuchun; Yan, Bing; Liu, Aihua; Yang, Yujun; Guo, Fuming; Ding, Dajun

    2017-12-01

    Controlling the molecular axis offers additional ways to study molecular ionization and dissociation in strong laser fields. We measure the ionization and dissociation yields of aligned polar CH3X (X =I , Br) molecules in a linearly polarized femtosecond laser field. The current data show that maximum ionization occurs when the laser polarization is perpendicular to the molecular C -X axis, and dissociation prefers to occur at the laser polarization parallel to the C -X axis. The observed angular distributions suggest that the parent ions are generated by ionization from the HOMO. The angular distribution of fragment ions indicates that dissociation occurs mainly from an ionic excited state produced by ionization from the HOMO-1.

  3. Simulation of enhanced deposition due to magnetic field alignment of ellipsoidal particles in a lung bifurcation.

    Science.gov (United States)

    Martinez, R C; Roshchenko, A; Minev, P; Finlay, W H

    2013-02-01

    Aerosolized chemotherapy has been recognized as a potential treatment for lung cancer. The challenge of providing sufficient therapeutic effects without reaching dose-limiting toxicity levels hinders the development of aerosolized chemotherapy. This could be mitigated by increasing drug-delivery efficiency with a noninvasive drug-targeting delivery method. The purpose of this study is to use direct numerical simulations to study the resulting local enhancement of deposition due to magnetic field alignment of high aspect ratio particles. High aspect ratio particles were approximated by a rigid ellipsoid with a minor diameter of 0.5 μm and fluid particle density ratio of 1,000. Particle trajectories were calculated by solving the coupled fluid particle equations using an in-house micro-macro grid finite element algorithm based on a previously developed fictitious domain approach. Particle trajectories were simulated in a morphologically realistic geometry modeling a symmetrical terminal bronchiole bifurcation. Flow conditions were steady inspiratory air flow due to typical breathing at 18 L/min. Deposition efficiency was estimated for two different cases: [1] particles aligned with the streamlines and [2] particles with fixed angular orientation simulating the magnetic field alignment of our previous in vitro study. The local enhancement factor defined as the ratio between deposition efficiency of Case [1] and Case [2] was found to be 1.43 and 3.46 for particles with an aspect ratio of 6 and 20, respectively. Results indicate that externally forcing local alignment of high aspect ratio particles can increase local deposition considerably.

  4. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

    Science.gov (United States)

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  5. Oxygen plasma assisted end-opening and field emission enhancement in vertically aligned multiwall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mathur, A. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom); Roy, S.S., E-mail: sinharoy@ualberta.ca [Department of Mechanical Engineering, University of Alberta, Edmonton, T6T 2G8 (Canada); Hazra, K.S. [Department of Physics, IIT Bombay, Powai, Mumbai-400076 (India); Wadhwa, S. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom); Ray, S.C. [School of Physics, University of the Witwatersrand, WITS 2050, Johannesburg (South Africa); Mitra, S.K. [Department of Mechanical Engineering, University of Alberta, Edmonton, T6T 2G8 (Canada); Misra, D.S. [Department of Physics, IIT Bombay, Powai, Mumbai-400076 (India); McLaughlin, J.A. [NIBEC, School of Engineering, University of Ulster, Jordanstown, BT37 0QB (United Kingdom)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer We showed Ar/O{sub 2} plasma can be effective for the end opening of aligned CNTs. Black-Right-Pointing-Pointer The field emission property was dramatically enhanced after plasma modification. Black-Right-Pointing-Pointer Microstructures were clearly understood by Raman and SEM analysis. Black-Right-Pointing-Pointer Surface wet-ability at various functionalised conditions was studied. - Abstract: This paper highlights the changes in micro-structural and field emission properties of vertically aligned carbon nanotubes (VACNTs) via oxygen plasma treatment. We find that exposure of very low power oxygen plasma (6 W) at 13.56 MHz for 15-20 min, opens the tip of vertically aligned CNTs. Scanning electron microscopy and transmission electron microscopy images were used to identify the quality and micro-structural changes of the nanotube morphology and surfaces. Raman spectra showed that the numbers of defects were increased throughout the oxygen plasma treatment process. In addition, the hydrophobic nature of the VACNTs is altered significantly and the contact angle decreases drastically from 110 Degree-Sign to 40 Degree-Sign . It was observed that the electron field emission (EFE) characteristics are significantly enhanced. The turn-on electric field (ETOE) of CNTs decreased from {approx}0.80 V {mu}m{sup -1} (untreated) to {approx}0.60 V {mu}m{sup -1} (oxygen treated). We believe that the open ended VACNTs would be immensely valuable for applications such as micro/nanofluidic based filtering elements and display devices.

  6. Field-free molecular alignment probed by the free electron laser in Hamburg (FLASH)

    Energy Technology Data Exchange (ETDEWEB)

    Johnsson, P; Rouzee, A; Siu, W; Huismans, Y; Vrakking, M J J [FOM Institute for Atomic and Molecular Physics (AMOLF), Science Park 113, 1098 XG Amsterdam (Netherlands); Lepine, F [Universite Lyon 1, CNRS, LASIM, UMR 5579, 43 bvd. du 11 novembre 1918, F-69622 Villeurbanne (France); Marchenko, T [Laboratoire d' Optique Applique, ENSTA/Ecole Polytechnique, Chemin de la Huniere, 91761 Palaiseau (France); Duesterer, S; Tavella, F; Stojanovic, N; Azima, A; Treusch, R [Hamburger Synchrotronstrahlungslabor (HASYLAB) at Deutsches Elektronen-Synchrotron (DESY) Notkestrasse 85, D-22607 Hamburg (Germany); Kling, M F [Max-Planck Institut fuer Quantenoptik, Hans-Kopfermann Strasse 1, D-85748 Garching (Germany)], E-mail: per.johnsson@fysik.lth.se

    2009-07-14

    High flux extreme ultraviolet (XUV) sources like the free electron laser (FEL) in Hamburg (FLASH) offer the possibility of diffractive imaging of small objects. Irrespective of whether the diffraction is based on the detection of photons or photoelectrons, it is required that the measurement is done in the reference frame of the molecule meaning that, for a sample of several molecules, it is necessary to pre-align the molecules in the sample. As a step towards performing molecular frame diffraction experiments, we report experiments on field-free molecular alignment performed at FLASH. The impulsive alignment induced by a 100 fs near-infrared laser pulse in a rotationally cold CO{sub 2} sample is characterized by ionizing and dissociating the molecules with a time-delayed XUV-FEL pulse. The time-dependent angular distributions of ionic fragments measured by a velocity map imaging spectrometer exhibit rapid changes associated with the induced rotational dynamics. The experimental results show hints of a dissociation process that depends nonlinearly on the XUV intensity.

  7. Alignment of SWNTs by protein-ligand interaction of functionalized magnetic particles under low magnetic fields.

    Science.gov (United States)

    Park, Tae Jung; Park, Jong Pil; Lee, Seok Jae; Jung, Dae-Hwan; Ko, Young Koan; Jung, Hee-Tae; Lee, Sang Yup

    2011-05-01

    Carbon nanotubes (CNTs) have attracted considerable attention for applications using their superior mechanical, thermal and electrical properties. A simple method to controllably align single-walled CNTs (SWNTs) by using magnetic particles embedded with superparamagnetic iron oxide as an accelerator under the magnetic field was developed. The functionalization of SWNTs using biotin, interacted with streptavidin-coupled magnetic particles (micro-to-nano in diameter), and layer-by-layer assembly were performed for the alignment of a particular direction onto the clean silicon and the gold substrate at very low magnetic forces (0.02-0.89 T) at room temperature. The successful alignment of the SWNTs with multi-layer film was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By changing the orientation and location of the substrates, crossed-networks of SWNTs-magnetic particle complex could easily be fabricated. We suggest that this approach, which consists of a combination of biological interaction among streptavidin-biotin and magnetite particles, should be useful for lateral orientation of individual SWNTs with controllable direction.

  8. Studies of currents and electric fields in the auroral zone ionosphere using radar auroral backscatter

    International Nuclear Information System (INIS)

    Greenwald, R.A.

    1980-01-01

    During the 1970s several advances have been made in the understanding of radar aurora. Recent VHF studies have shown that Doppler data obtained from radar auroral backscatter can be used to measure the E-region electron drift velocity, the F-region plasma velocity, and the ionospheric electric field. This type of measurement is particularly valuable when it is made with dual auroral radar systems similar to STARE (Scandinavian Twin Auroral Radar Experiment). Over the past two years STARE has been used to study electric field patterns associated with electrojet and field-aligned currents, magnetospheric convection, the Harang discontinuity, Pc5 micropulsations, and the substorm expansion phase. (Auth.)

  9. Can primordial magnetic fields seeded by electroweak strings cause an alignment of quasar axes on cosmological scales?

    Science.gov (United States)

    Poltis, Robert; Stojkovic, Dejan

    2010-10-15

    The decay of nontopological electroweak strings may leave an observable imprint in the Universe today in the form of primordial magnetic fields. Protogalaxies preferentially tend to form with their axis of rotation parallel to an external magnetic field, and, moreover, an external magnetic field produces torque which tends to align the galaxy axis with the magnetic field. We demonstrate that the shape of a magnetic field left over from two looped electroweak strings can explain the observed nontrivial alignment of quasar polarization vectors and make predictions for future observations.

  10. Alternating current impedance spectroscopic analysis of biofunctionalized vertically-aligned silica nanospring surface for biosensor applications

    Science.gov (United States)

    Timalsina, Yukta P.

    In this dissertation, a process of vertically-aligned (silica) nanosprings (VANS) based biosensor development is presented. Alternating current (AC) impedance spectroscopy has been used to analyze sensor response as a function of saline phosphate (SP) buffer and biological solutions. The sensor is a parallel plate capacitor consisting of two glass substrates coated with indium tin oxide (ITO), where the VANS [or randomly-aligned nanosprings (RANS)] grown on one substrate serve as the dielectric spacer layer. The response of a VANS device as a function of ionic concentration in SP buffer was examined and an equivalent circuit model was developed. The results demonstrated that VANS sensors exhibited greater sensitivity to the changes in SP concentration relative to the ITO sensors, which serve as controls. The biofunctionalized VANS surface via physisorption and the cross-linker method demonstrates the repeatability, specificity, and selectivity of the binding. The physisorption of biotinylated immunoglobulin G (B-IgG) onto the VANS surface simplifies the whole sensing procedure for the detection of glucose oxidase, since the avidin-conjugated glucose oxidase (Av-GOx) can directly be immobilized on the B-IgG. The cross linker method involves the covalent attachment of antibodies onto the functionalized VANS surface via imine bond. The experiments revealed that the VANS sensor response is solely the result of the interaction of target molecule i.e. mouse IgG with the probe layer, i.e. goat antimouse IgG (GalphaM IgG). It was determined that VANS-based sensors exhibit a greater magnitude of change between successive bio-layers relative to the controls above 100 Hz, which indicates that the addition of biomolecules inhibits the diffusion of ions and changes the effective dielectric response of the VANS via biomolecular polarization. The study of ionic transport in nanosprings suggested that conductance follows a scaling law. It was demonstrated that a VANS-based device

  11. Characterization and performance of a field aligned ion cyclotron range of frequency antenna in Alcator C-Moda)

    Science.gov (United States)

    Wukitch, S. J.; Garrett, M. L.; Ochoukov, R.; Terry, J. L.; Hubbard, A.; Labombard, B.; Lau, C.; Lin, Y.; Lipschultz, B.; Miller, D.; Reinke, M. L.; Whyte, D.; Alcator C-Mod Team

    2013-05-01

    Ion cyclotron range of frequency (ICRF) heating is expected to provide auxiliary heating for ITER and future fusion reactors where high Z metallic plasma facing components (PFCs) are being considered. Impurity contamination linked to ICRF antenna operation remains a major challenge particularly for devices with high Z metallic PFCs. Here, we report on an experimental investigation to test whether a field aligned (FA) antenna can reduce impurity contamination and impurity sources. We compare the modification of the scrape of layer (SOL) plasma potential of the FA antenna to a conventional, toroidally aligned (TA) antenna, in order to explore the underlying physics governing impurity contamination linked to ICRF heating. The FA antenna is a 4-strap ICRF antenna where the current straps and antenna enclosure sides are perpendicular to the total magnetic field while the Faraday screen rods are parallel to the total magnetic field. In principle, alignment with respect to the total magnetic field minimizes integrated E|| (electric field along a magnetic field line) via symmetry. A finite element method RF antenna model coupled to a cold plasma model verifies that the integrated E|| should be reduced for all antenna phases. Monopole phasing in particular is expected to have the lowest integrated E||. Consistent with expectations, we observed that the impurity contamination and impurity source at the FA antenna are reduced compared to the TA antenna. In both L and H-mode discharges, the radiated power is 20%-30% lower for a FA-antenna heated discharge than a discharge heated with the TA-antennas. However, inconsistent with expectations, we observe RF induced plasma potentials (via gas-puff imaging and emissive probes to be nearly identical for FA and TA antennas when operated in dipole phasing). Moreover, the highest levels of RF-induced plasma potentials are observed using monopole phasing with the FA antenna. Thus, while impurity contamination and sources are indeed

  12. Identification of BKCa channel openers by molecular field alignment and patent data-driven analysis

    Directory of Open Access Journals (Sweden)

    Yaseen Gigani

    2016-01-01

    Full Text Available In this work, we present the first comprehensive molecular field analysis of patent structures on how the chemical structure of drugs impacts the biological binding. This task was formulated as searching for drug structures to reveal shared effects of substitutions across a common scaffold and the chemical features that may be responsible. We used the SureChEMBL patent database, which provides search of the patent literature using keyword-based functionality, as a query engine. The extraction of data of the BKCa channel openers and aligning them for molecular field similarity with newly designed structures did provide a probable validation method with accurate values. Therefore, in an attempt to increase the true positives, we report a procedure that functions on a multiple analyses modeled on molecular field similarity and common sub-structural search with consensus scoring and high confidence values to obtain greater accuracy during conventional virtual screening.

  13. Electrical alignment of antenna coordinate system in a planar near-field setup

    DEFF Research Database (Denmark)

    Mynster, Anders P.; Nielsen, Jeppe Majlund; Pivnenko, Sergey

    2011-01-01

    In this paper, a simple and efficient electrical alignment procedure known as flip-test is adapted and applied to check and correct two errors in the mechanical setup of a planar near-field system: the mis-pointing of the z-axis of the antenna coordinate system with respect to the scan plane...... and the displacement of the center point of the scan plane with respect to the z-axis of the antenna coordinate system. Simulations of the errors and their correction algorithms were carried out with different models of antennas composed of Hertzian dipoles and an optimum algorithm was then selected. The proposed...

  14. Topography, Astronomy And Dynastic History In The Alignments Of The Pyramid Fields Of The Old Kingdom

    Science.gov (United States)

    Magli, G.

    It is known since the 19 century that in the layout of the pyramid field of the pharaohs of the 4th Egyptian dynasty at Giza, a "main axis" exists. Indeed, the south-east corners of these monuments align towards the site of the temple of Heliopolis, which was plainly visible in ancient times. It was later discovered that a similar situation occurs in the main pyramid field of the subsequent dynasty at Abu Sir. Here, the north-west corners of three chronologically successive pyramids again voluntarily align towards Heliopolis. However, the temple was in this case not visible, due to the rock outcrop- today occupied by the Cairo citadel - which blocks the view. In the present paper, a interdisciplinary approach based on historical, topographical and archaeoastronomical analysis is developed in an attempt at understanding such peculiar features, which governed from the very beginning the planning of these wonderful monuments. A general pattern actually arises, which appears to have inspired the choice of the sites and the disposition on the ground of almost all the funerary complexes of the kings during the Old Kingdom. In particular, this pattern helps to explain the choices in the location of the funerary complexes of Niuserre in Abusir, of Unas in Saqqara and of the kings of the 6th dynasty at south Saqqara.

  15. Radar observations of artificial E-region field-aligned irregularities

    Directory of Open Access Journals (Sweden)

    E. Nossa

    2009-07-01

    Full Text Available Artificial E region field aligned plasma density irregularities (FAIs were generated using HAARP in four different experimental modes and observed with a coherent scatter radar imager located 450 km to the southwest where it could detect field-aligned backscatter. The experiments were conducted in July of 2008, during the Polar Aeronomy and Radio Science Summer School (PARS, during quiet conditions in the daytime when the E layer was dense and absorption was modest. The echoes observed during zenith and magnetic zenith heating experiments were deflected from their nominally anticipated horizontal positions toward the midpoint position. The occurrence of hysteresis when heating with amplitude modulated pulses implied the development of the resonance instability, although the threshold for the onset of instability appeared to be higher than what has been predicted theoretically. Heating experiments involving pump frequencies slightly above and below the second electron gyroharmonic frequency produced no significant differences in the observed echoes. Finally, heating with a pump frequency slightly above the E region critical frequency appears to have produced FAIs at two distinct altitudes where the upper-hybrid resonance condition could be satisfied.

  16. Electric fields associated with transient surface currents

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1992-01-01

    The boundary condition to be fulfilled by the potential functions associated with a transient surface current is derived and expressed in terms of generalized orthogonal coordinates. From the analysis, it can be deduced that the use of the method of separation of variables is restricted to three ...

  17. Field primatology of today: current ethical issues.

    Science.gov (United States)

    MacKinnon, K C; Riley, E P

    2010-09-01

    As members of professional organizations such as American Society of Primatologists (ASP) and the International Primatological Society (IPS), primatologists must adhere to a set of nonhuman primate-focused principles outlined in resolutions and policy statements on, for example, the ethical treatment of nonhuman primates. Those of us that work in the field must also address issues such as the protection of primate health in the wild and the conservation of wild primate populations. Moreover, we increasingly find ourselves in complex situations where we must balance human and nonhuman primate needs and interests. The selection of commentary pieces in this edition of the American Journal of Primatology originated from presentations given in the symposium, Field Primatology of Today: Navigating the Ethical Landscape, held at the 32nd Annual Meeting of the American Society of Primatologists (ASP) in September 2009. The goals of that symposium and these resulting commentary pieces are threefold: (1) to revive a discussion of key contemporary ethical issues faced by field primatologists, (2) to highlight the need for centrally placed ethical considerations in various facets of our professional lives, particularly research and teaching, and (3) to consider what a comprehensive ethical code that addresses all of these issues might look like. (c) 2010 Wiley-Liss, Inc.

  18. Field-Effect Transistors Based on Networks of Highly Aligned, Chemically Synthesized N = 7 Armchair Graphene Nanoribbons.

    Science.gov (United States)

    Passi, Vikram; Gahoi, Amit; Senkovskiy, Boris V; Haberer, Danny; Fischer, Felix R; Grüneis, Alexander; Lemme, Max C

    2018-03-28

    We report on the experimental demonstration and electrical characterization of N = 7 armchair graphene nanoribbon (7-AGNR) field effect transistors. The back-gated transistors are fabricated from atomically precise and highly aligned 7-AGNRs, synthesized with a bottom-up approach. The large area transfer process holds the promise of scalable device fabrication with atomically precise nanoribbons. The channels of the FETs are approximately 30 times longer than the average nanoribbon length of 30 nm to 40 nm. The density of the GNRs is high, so that transport can be assumed well-above the percolation threshold. The long channel transistors exhibit a maximum I ON / I OFF current ratio of 87.5.

  19. Large-scale aligned silicon carbonitride nanotube arrays: Synthesis, characterization, and field emission property

    International Nuclear Information System (INIS)

    Liao, L.; Xu, Z.; Liu, K. H.; Wang, W. L.; Liu, S.; Bai, X. D.; Wang, E. G.; Li, J. C.; Liu, C.

    2007-01-01

    Large-scale aligned silicon carbonitride (SiCN) nanotube arrays have been synthesized by microwave-plasma-assisted chemical vapor deposition using SiH 4 , CH 4 , and N 2 as precursors. The three elements of Si, C, and N are chemically bonded with each other and the nanotube composition can be adjusted by varying the SiH 4 concentration, as revealed by electron energy loss spectroscopy and x-ray photoelectron spectroscopy. The evolution of microstructure of the SiCN nanotubes with different Si concentrations was characterized by high-resolution transmission electron microscopy and Raman spectroscopy. The dependence of field emission characteristics of the SiCN nanotubes on the composition has been investigated. With the increasing Si concentration, the SiCN nanotube exhibits more favorable oxidation resistance, which suggests that SiCN nanotube is a promising candidate as stable field emitter

  20. Magnetic Field Alignment of PS-P4VP: a Non-Liquid Crystalline Coil-Coil Block Copolymer

    Science.gov (United States)

    Rokhlenko, Yekaterina; Zhang, Kai; Larson, Steven; Gopalan, Padma; O'Hern, Corey; Osuji, Chinedum

    2015-03-01

    Magnetic fields provide the ability to control alignment of self-assembled soft materials such as block copolymers. Most prior work in this area has relied on the presence of ordered assemblies of anisotropic liquid crystalline species to ensure sufficient magnetic anisotropy to drive alignment. Recent experiments with poly(styrene-b-4-vinylpyridine), a non-liquid crystalline BCP, however, show field-induced alignment of a lamellar microstructure during cooling across the order-disorder transition. Using in situ x-ray scattering, we examine the roles of field strength and cooling rate on the alignment response of this low MW coil-coil BCP. Alignment is first observed at field strengths as low as 1 Tesla and improves markedly with both increasing field strength and slower cooling. We present a geometric argument to illustrate the origin of a finite, non-trivial magnetic susceptibility anisotropy for highly stretched surface-tethered polymer chains and corroborate this using coarse-grained molecular dynamics simulations. We rationalize the magnetic field response of the system in terms of the mobility afforded by the absence of entanglements, the intrinsic anisotropy resulting from the stretched polymer chains and sterically constrained conjugated rings, and the large grain size in these low molecular weight materials.

  1. Rotating magnetic field current drive-theory and experiment

    International Nuclear Information System (INIS)

    Donnelly, I.J.

    1989-01-01

    Rotating magnetic fields have been used to drive plasma current and establish a range of compact torus configurations, named rotamaks. The current drive mechanism involves a ponderomotive force acting on the electron fluid. Recent extensions of the theory indicate that this method is most suitable for driving currents in directions perpendicular to the steady magnetic fields

  2. Self-centering fiber alignment structures for high-precision field installable single-mode fiber connectors

    Science.gov (United States)

    Van Erps, Jürgen; Ebraert, Evert; Gao, Fei; Vervaeke, Michael; Berghmans, Francis; Beri, Stefano; Watté, Jan; Thienpont, Hugo

    2014-05-01

    constants of the order of 104N=m are found to be compatible with a proof stress of 70 M Pa. We show the successful prototyping of 3-spring fiber alignment structures using deep proton writing and investigate their compatibility with replication techniques such as hot embossing and injection moulding. Fiber insertion in our self-centering alignment structures is achieved by means of a dedicated interferometric setup allowing assessment of the fiber facet quality, of the fiber's position in relation to the connector's front and of the spring deformation during fiber insertion. These self-centering structures have the potential to become the basic building blocks for a new generation of field-installable connectors, ultimately breaking the current paradigm of ferrule-based connectivity requiring extensive pre-engineering and highly specialized manpower for field deployment.

  3. FENICIA: a generic plasma simulation code using a flux-independent field-aligned coordinate approach

    International Nuclear Information System (INIS)

    Hariri, Farah

    2013-01-01

    The primary thrust of this work is the development and implementation of a new approach to the problem of field-aligned coordinates in magnetized plasma turbulence simulations called the FCI approach (Flux-Coordinate Independent). The method exploits the elongated nature of micro-instability driven turbulence which typically has perpendicular scales on the order of a few ion gyro-radii, and parallel scales on the order of the machine size. Mathematically speaking, it relies on local transformations that align a suitable coordinate to the magnetic field to allow efficient computation of the parallel derivative. However, it does not rely on flux coordinates, which permits discretizing any given field on a regular grid in the natural coordinates such as (x, y, z) in the cylindrical limit. The new method has a number of advantages over methods constructed starting from flux coordinates, allowing for more flexible coding in a variety of situations including X-point configurations. In light of these findings, a plasma simulation code FENICIA has been developed based on the FCI approach with the ability to tackle a wide class of physical models. The code has been verified on several 3D test models. The accuracy of the approach is tested in particular with respect to the question of spurious radial transport. Tests on 3D models of the drift wave propagation and of the Ion Temperature Gradient (ITG) instability in cylindrical geometry in the linear regime demonstrate again the high quality of the numerical method. Finally, the FCI approach is shown to be able to deal with an X-point configuration such as one with a magnetic island with good convergence and conservation properties. (author) [fr

  4. Promotion of Myogenic Maturation by Timely Application of Electric Field Along the Topographical Alignment.

    Science.gov (United States)

    Ko, Ung Hyun; Park, Sukhee; Bang, Hyunseung; Kim, Mina; Shin, Hyunjun; Shin, Jennifer H

    2018-05-01

    Engineered muscular substitutes can restore the impaired muscle functions when integrated properly into the host tissue. To generate functional muscles with sufficient contractility at the site of transplant, the in vitro construction of fully differentiated muscle fibers would be desired. Many previous reports have identified either topographical alignment or electrical stimulation as an effective tool to promote myogenic differentiation. However, optimization of spatial and temporal arrangement of these two physical cues for better differentiation and maturation of skeletal muscles has not been investigated. In this article, we introduce a novel cell culture system that allows simultaneous application of these two independent directional cues at both orthogonal and parallel arrangements. We then show that the parallel arrangement of the aligned topography and the electric field synergistically facilitates better differentiation and maturation of C2C12, generating myotubes with more fused nuclei. Addition of the electric stimulation at the late stage of myogenic differentiation is found to further improve cell fusion to form multinucleate myotubes through a phosphatidylinositol-3-OH-kinase-dependent pathway. As such, we successfully demonstrated that the combined stimulation of topographical and electrical cues could effectively enhance both myogenic differentiation and maturation in a temporal and orientation-dependent manner, providing the basis for therapeutic strategies for regenerative tissue engineering.

  5. Representations of currents and magnetic fields in anisotropic magnetohydrostatic plasma. 2. General theory and examples

    International Nuclear Information System (INIS)

    Heinemann, M.; Pontius, D.H. Jr.

    1991-01-01

    The authors develop a general treatment of field-aligned currents in quasi-static adiabatic plasma. The formalism is an extension of an earlier analysis (Heinemann, 1990) to include electric and gravitational fields. The assumption that the particle motions are adiabatic along the magnetic field leads to an expression for the total current density that is a generalization of expressions given by Grad (1964) and Vasyliunas (1970). The current density is a vector function of the gradients of the field line constants characterizing the plasma and the gradients of field line integrals of the partial derivations of the parallel pressure with respect to the constants. The use of the expression as the current source in Ampere's law leads to an equation governing the equilibrium of the system of plasma and magnetic field. Examples based on bi-Maxwellian distribution functions suggest that the effects of thermal anisotropy can be about as large as the currents due to isotropic plasma and that the effects of parallel electric field are of the same order of magnitude

  6. Observations of field-aligned energetic electron and ion distributions near the magnetopause at geosynchronous orbit

    International Nuclear Information System (INIS)

    Korth, A.; Kremser, G.; Daly, P.W.; Amata, E.

    1982-01-01

    On August 28, 1978, the dayside magnetopause crossed the geosynchronous satellite GEOS 2 several times during a geomagnetically disturbed period, and clear signatures of the interconnection of field lines through the magnetopause were observed. The MPAE particle spectrometer provided high time resolution observations of the distribution of energetic electrons (E>22 keV) and ions (E>27 keV). Magnetometer data were used to determine the location of GEOS 2 relative to the magnetopause. The pitch angle distributions of ions and electrons were found to be strongly asymmetric with respect to 90 0 , and the asymmetries have been interpreted in terms of field-aligned particle streaming. Evidence is provided for the first time for electron streaming inside the magnetopause which continues for many bounce periods. It is concluded that magnetospheric field lines opened, at least for brief time intervals, as a consequence of interconnection with magnetosheath field lines. Comparisons of electron spectra provide evidence that the streaming electrons observed in the magnetosheath originate in the magnetosphere

  7. Laser-induced field-free alignment of the OCS molecule

    International Nuclear Information System (INIS)

    Loriot, V; Tzallas, P; Benis, E P; Hertz, E; Lavorel, B; Charalambidis, D; Faucher, O

    2007-01-01

    We investigate the dynamical alignment of jet-cooled OCS molecules induced by a short laser pulse. The alignment is measured through the orientational contribution of the optical Kerr effect using a second weak laser pulse as a probe. Maximum alignment is observed at conditions close to saturation of ionization. The results are analysed with a quantum mechanical model solving for the rotational dynamics

  8. Controllable deposition distance of aligned pattern via dual-nozzle near-field electrospinning

    Science.gov (United States)

    Wang, Zhifeng; Chen, Xindu; Zeng, Jun; Liang, Feng; Wu, Peixuan; Wang, Han

    2017-03-01

    For large area micro/nano pattern printing, multi-nozzle electrohydrodynamic (EHD) printing setup is an efficient method to boost productivity in near-field electrospinning (NFES) process. And controlling EHD multi-jet accurate deposition under the interaction of nozzles and other parameters are crucial concerns during the process. The influence and sensitivity of various parameters such as the needle length, needle spacing, electrode-to-collector distance, voltage etc. on the direct-write patterning performance was investigated by orthogonal experiments with dual-nozzle NFES setup, and then the deposition distance estimated based on a novel model was compared with measurement results and proven. More controllable deposition distance and much denser of aligned naofiber can be achieved by rotating the dual-nozzle setup. This study can be greatly contributed to estimate the deposition distance and helpful to guide the multi-nozzle NFES process to accurate direct-write pattern in manufacturing process in future.

  9. Field emission from a composite structure consisting of vertically aligned single-walled carbon nanotubes and carbon nanocones

    International Nuclear Information System (INIS)

    Yeh, C M; Chen, M Y; Hwang, J; Gan, J-Y; Kou, C S

    2006-01-01

    Vertically aligned single-walled carbon nanotubes (VA-SWCNTs) have been fabricated on carbon nanocones (CNCs) in a gravity-assisted chemical vapour deposition (CVD) process. The CNCs with nanoscale Co particles at the top were first grown on the Co/Si(100) substrate biased at 350 V in a plasma enhanced chemical vapour deposition process. The CNCs typically are ∼200 nm in height, and their diameters are ∼100 nm near the bottom and ∼10 nm at the top. The nanoscale Co particles ∼10 nm in diameter act as catalysts which favour the growth of VA-SWCNTs out of CNCs at 850 0 C in the gravity-assisted CVD process. The average length and the growth time of VA-SWCNTs are ∼150 nm and 1.5 min, equivalent to a growth rate of ∼6 μm h -1 . The diameters of VA-SWCNTs are estimated to be 1.2-2.1 nm. When VA-SWCNTs are fabricated on CNCs, the turn-on voltage is reduced from 3.9 to 0.7 V μm -1 and the emission current density at the electric field of 5 V μm -1 is enhanced by a factor of more than 200. The composite VA-SWCNT/CNC structure is potentially an excellent field emitter. The emission stability of the VA-SWCNT/CNC field emitter is discussed

  10. Plasma Deposited SiO2 for Planar Self-Aligned Gate Metal-Insulator-Semiconductor Field Effect Transistors on Semi-Insulating InP

    Science.gov (United States)

    Tabory, Charles N.; Young, Paul G.; Smith, Edwyn D.; Alterovitz, Samuel A.

    1994-01-01

    Metal-insulator-semiconductor (MIS) field effect transistors were fabricated on InP substrates using a planar self-aligned gate process. A 700-1000 A gate insulator of Si02 doped with phosphorus was deposited by a direct plasma enhanced chemical vapor deposition at 400 mTorr, 275 C, 5 W, and power density of 8.5 MW/sq cm. High frequency capacitance-voltage measurements were taken on MIS capacitors which have been subjected to a 700 C anneal and an interface state density of lxl0(exp 11)/eV/cq cm was found. Current-voltage measurements of the capacitors show a breakdown voltage of 107 V/cm and a insulator resistivity of 10(exp 14) omega cm. Transistors were fabricated on semi-insulating InP using a standard planar self-aligned gate process in which the gate insulator was subjected to an ion implantation activation anneal of 700 C. MIS field effect transistors gave a maximum extrinsic transconductance of 23 mS/mm for a gate length of 3 microns. The drain current drift saturated at 87.5% of the initial current, while reaching to within 1% of the saturated value after only 1x10(exp 3). This is the first reported viable planar InP self-aligned gate transistor process reported to date.

  11. Galactic cosmic ray gradients, field-aligned and latitudinal, among Voyagers 1/2 and IMP-8

    Science.gov (United States)

    Roelof, E. C.; Decker, R. B.; Krimigis, S. M.; Venkatesan, D.; Lazarus, A. J.

    1982-01-01

    The present investigation represents a summary of a comprehensive analysis of the same subject conducted by Roelof et al. (1981). It is pointed out that the tandem earth-Jupiter trajectories of the Voyager 1/2 spacecraft, combined with baseline measurements from the earth-orbiting IMP 7/8 spacecraft, provide the first opportunity for unambiguously separating latitude from radial or field-aligned effects in galactic cosmic ray gradients. Attention is given to the method of data analysis, and the separation of field-aligned and latitudinal gradients. It is found that latitudinal gradients approximately equal to or greater than 1 percent per deg in the cosmic ray intensity were a common feature of the interplanetary medium between 1 and 5 AU in 1977-78. Except in the most disturbed periods, cosmic ray intensities are well-ordered in field-aligned structures.

  12. Progress in ETA-II magnetic field alignment using stretched wire and low energy electron beam techniques

    International Nuclear Information System (INIS)

    Griffith, L.V.; Deadrick, F.J.

    1991-01-01

    Flux line alignment of the solenoidal focus magnets used on the ETA-II linear induction accelerator is a key element leading to a reduction of beam corkscrew motion. Two techniques have been used on the ETA-II accelerator to measure and establish magnet alignment. A low energy electron beam has been used to directly map magnetic field lines, and recent work has utilized a pulsed stretched wire technique to measure magnet tilts and offsets with respect to a reference axis. This paper reports on the techniques used in the ETA-II accelerator alignment, and presents results from those measurements which show that accelerator is magnetically aligned to within ∼ ± 200 microns

  13. Image stack alignment in full-field X-ray absorption spectroscopy using SIFT_PyOCL.

    Science.gov (United States)

    Paleo, Pierre; Pouyet, Emeline; Kieffer, Jérôme

    2014-03-01

    Full-field X-ray absorption spectroscopy experiments allow the acquisition of millions of spectra within minutes. However, the construction of the hyperspectral image requires an image alignment procedure with sub-pixel precision. While the image correlation algorithm has originally been used for image re-alignment using translations, the Scale Invariant Feature Transform (SIFT) algorithm (which is by design robust versus rotation, illumination change, translation and scaling) presents an additional advantage: the alignment can be limited to a region of interest of any arbitrary shape. In this context, a Python module, named SIFT_PyOCL, has been developed. It implements a parallel version of the SIFT algorithm in OpenCL, providing high-speed image registration and alignment both on processors and graphics cards. The performance of the algorithm allows online processing of large datasets.

  14. The impact of capacitor bank inrush current on field emission current in vacuum

    NARCIS (Netherlands)

    Koochack-Zadeh, M.; Hinrichsen, V.; Smeets, R.P.P.; Lawall, A.

    2010-01-01

    Field emission current measurements during the recovery voltage are investigated to understand the origin of restrikes in vacuum interrupters in case of the interruption of capacitive loads. Measurement and analysis of very small field emission currents (0.01 - 1 mA) from the current zero crossing

  15. Magnetic Field of Conductive Objects as Superposition of Elementary Eddy Currents and Eddy Current Tomography

    Science.gov (United States)

    Sukhanov, D. Ya.; Zav'yalova, K. V.

    2018-03-01

    The paper represents induced currents in an electrically conductive object as a totality of elementary eddy currents. The proposed scanning method includes measurements of only one component of the secondary magnetic field. Reconstruction of the current distribution is performed by deconvolution with regularization. Numerical modeling supported by the field experiments show that this approach is of direct practical relevance.

  16. High field, low current operation of engineering test reactors

    International Nuclear Information System (INIS)

    Schwartz, J.; Cohn, D.R.; Bromberg, L.; Williams, J.E.C.

    1987-06-01

    Steady state engineering test reactors with high field, low current operation are investigated and compared to high current, lower field concepts. Illustrative high field ETR parameters are R = 3 m, α ∼ 0.5 m, B ∼ 10 T, β = 2.2% and I = 4 MA. For similar wall loading the fusion power of an illustrative high field, low current concept could be about 50% that of a lower field device like TIBER II. This reduction could lead to a 50% decrease in tritium consumption, resulting in a substantial decrease in operating cost. Furthermore, high field operation could lead to substantially reduced current drive requirements and cost. A reduction in current drive source power on the order of 40 to 50 MW may be attainable relative to a lower field, high current design like TIBER II implying a possible cost savings on the order of $200 M. If current drive is less efficient than assumed, the savings could be even greater. Through larger β/sub p/ and aspect ratio, greater prospects for bootstrap current operation also exist. Further savings would be obtained from the reduced size of the first wall/blanket/shield system. The effects of high fields on magnet costs are very dependent on technological assumptions. Further improvements in the future may lie with advances in superconducting and structural materials

  17. Coordination of Project and Current Activities on the Basis of the Strategy Alignment Metamodel in the Oil and Gas Company

    Directory of Open Access Journals (Sweden)

    R. Yu. Dashkov

    2017-01-01

    Full Text Available Purpose: the purpose of this article is to describe the Strategy Alignment Metamodel of the project and current activities, which allows us to connect the Goals and Strategies for Phases of the project with the Goals and Strategies of the company at all levels of the organization through targeted measurement and application of Interpretive Models. Building Networks of Goals and Strategies, and adopting organizational solutions, you coordinate the interaction of the Project office and departments of the company. This methodology is based on a Logical Rationale of the Contexts and Assumptions for establishing Goals and Strategies both for the project and for the company, and on preparation of Contexts and Assumptions, Goals and Strategies Alignment Matrices, which provides a flexible adaptation to the internal and external environment in the process of selecting the most successful Strategies to achieve the Goals. Methods: this article is based on the concept of Goals-Questions-Metrics+ Strategies, which is adapted as another concept of strategic monitoring and control system of projects: Goals-Phases-Metrics+Strategies. These concepts have formed the basis of the Strategy Alignment Metamodel, where a technology of Phases Earned Value Management is used as a measurement system for the project activity, and Balanced scorecard is applied for current operations. Results: strategy Alignment Metamodel of the project and current activities of the company is proposed hereby. It uses modern strategic monitoring and control systems for projects: Goals-Phases-Metrics+Strategies, and for the company: Goals-Questions-Metrics+ Strategies. The interaction between these systems is based on Contexts and Assumptions, Goals and Strategies Alignment Matrices. The existence of such matrices greatly simplifies management decisions and prevents the risk of delays in the execution of project Phases based on rational participation and coordination of the company

  18. Power and momentum relations in rotating magnetic field current drive

    Energy Technology Data Exchange (ETDEWEB)

    Hugrass, W N [Flinders Univ. of South Australia, Bedford Park. School of Physical Sciences

    1984-01-01

    The use of rotating magnetic fields (RMF) to drive steady currents in plasmas involves a transfer of energy and angular momentum from the radio frequency source feeding the rotating field coils to the plasma. The power-torque relationships in RMF systems are discussed and the analogy between RMF current drive and the polyphase induction motor is explained. The general relationship between the energy and angular momentum transfer is utilized to calculate the efficiency of the RMF plasma current drive. It is found that relatively high efficiencies can be achieved in RMF current drive because of the low phase velocity and small slip between the rotating field and the electron fluid.

  19. S-matrix analysis of vibrational and alignment effects in intense-field multiphoton ionization of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Requate, A

    2007-03-15

    Theoretical analysis of the vibrational excitation of small molecules during multiphoton ionization in intense laser fields of optical and infrared frequencies. Analysis of the alignment dependence of the electron impact ionization of diatomic molecules in the presence of an intense laser field as the final step in the process of Nonsequential Double Ionization. Quantum mechanical description using S-matrix theory in Strong Field Approximation (SFA), i.e. beyond perturbation theory. (orig.)

  20. S-matrix analysis of vibrational and alignment effects in intense-field multiphoton ionization of molecules

    International Nuclear Information System (INIS)

    Requate, A.

    2007-03-01

    Theoretical analysis of the vibrational excitation of small molecules during multiphoton ionization in intense laser fields of optical and infrared frequencies. Analysis of the alignment dependence of the electron impact ionization of diatomic molecules in the presence of an intense laser field as the final step in the process of Nonsequential Double Ionization. Quantum mechanical description using S-matrix theory in Strong Field Approximation (SFA), i.e. beyond perturbation theory. (orig.)

  1. Effects of fluctuations and noise on the neutron monitor diurnal anisotropy. II. Non-field-aligned diffusion

    International Nuclear Information System (INIS)

    Owens, A.J.

    1977-01-01

    The effects of non-field-aligned diffusion (i.e., terms in the diffusion tensor proportional to the antisymmetric coefficient kappa/sub A/) on the observed day-to-day deviation of the diffusive diurnal anisotropy from the daily average magnetic field direction are considered. Using reasonable parameters for the diffusion of cosmic rays in interplanetary space, I show that these terms give a natural explanation for the angular difference between the anisotropy and field directions during normal quiet interplanetary epochs

  2. Massive Abelian gauge fields coupled with nonconserved currents

    International Nuclear Information System (INIS)

    Nakazato, Hiromichi; Namiki, Mikio; Yamanaka, Yoshiya; Yokoyama, Kan-ichi.

    1985-04-01

    A massive Abelian gauge field coupled with a nonconserved mass-changing current is described within the framework of canonical quantum theory with indefinite metric. In addition to the conventional Lagrange multiplier fields, another ghost field is introduced to preserve gauge invariance and unitarity of a physical S-matrix in the case of the nonconserved current. The renormalizability of the theory is explicitly shown in the sense of superpropagator approach for nonpolynomial Lagrangian theories. (author)

  3. Remote field eddy current testing of ferromagnetic tubes

    International Nuclear Information System (INIS)

    David, B.

    1990-01-01

    In order to test ferromagnetic tubes using internal probes, Intercontrole and the CEA have carried out theoretical and experimental works and developed a method to adapt the Remote Field Eddy Current technique which has been known and used for 30 years now. This document briefly recalls the basic principles of the Remote Field Eddy Current technique, the various steps of the works carried out and mainly describes examples of field inspection of ferromagnetic tubes and pipes [fr

  4. Photonic chiral current and its anomaly in a gravitational field

    International Nuclear Information System (INIS)

    Dolgov, A.D.; Khriplovich, I.B.; Vajnshtejn, A.I.; Zakharov, V.I.

    1988-01-01

    The notion of chirality for electromagnetic field which is conserved in interactions with gravitons is formulated. The correponding chiral current is the one-particle-state analogue of the Pauli-Lubansky vector. The anomaly of this current in an external gravitational field is found. The results obtained are used for the calculation of the electromagnetic radiative correction to the fermionic chiral anomaly in a gravitational field

  5. High-latitude dayside electric fields and currents during strong northward interplanetary magnetic field: Observations and model simulation

    International Nuclear Information System (INIS)

    Clauer, C.R.; Friis-Christensen, E.

    1988-01-01

    On July 23, 1983, the Interplanetary Magnetic Field turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, we observe the onset of the reconfiguration of the high-latitude ionospheric currents to occur about 3 min following the northward IMF encountering the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. Using a computer model in which the distribution of field-aligned current in the polar cleft is directly determined by the strength and orientation of the interplanetary electric field, we are able to simulate the time-varying pattern of ionospheric convection, including the onset of high-latitude ''reversed convection'' cells observed to form during the interval of strong northward IMF. These observations and the simulation results indicate that the dayside polar cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind. copyright American Geophysical Union 1988

  6. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A., E-mail: jrogers@illinois.edu [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Wahab, Muhammad A.; Alam, Muhammad A. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Yuhang [Institute of Solid Mechanics, Beihang University, Beijing 100191 (China); Tomic, Bojan [Department of Electrical Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Huang, Jiyuan [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Burns, Branden [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Song, Jizhou [Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027 (China); Huang, Yonggang [Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-04-07

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

  7. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A.; Wahab, Muhammad A.; Alam, Muhammad A.; Li, Yuhang; Tomic, Bojan; Huang, Jiyuan; Burns, Branden; Song, Jizhou; Huang, Yonggang

    2015-01-01

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups

  8. The optical manifestation of dispersive field-aligned bursts in auroral breakup arcs

    Science.gov (United States)

    Dahlgren, H.; Semeter, J. L.; Marshall, R. A.; Zettergren, M.

    2013-07-01

    High-resolution optical observations of a substorm expansion show dynamic auroral rays with surges of luminosity traveling up the magnetic field lines. Observed in ground-based imagers, this phenomenon has been termed auroral flames, whereas the rocket signatures of the corresponding energy dispersions are more commonly known as field-aligned bursts. In this paper, observations of auroral flames obtained at 50 frames/s with a scientific-grade Complementary Metal Oxide Semiconductor (CMOS) sensor (30° × 30° field of view, 30 m resolution at 120 km) are used to provide insight into the nature of the precipitating electrons similar to high-resolution particle detectors. Thanks to the large field of view and high spatial resolution of this system, it is possible to obtain a first-order estimate of the temporal evolution in altitude of the volume emission rate from a single sensor. The measured volume emission rates are compared with the sum of modeled eigenprofiles obtained for a finite set of electron beams with varying energy provided by the TRANSCAR auroral flux tube model. The energy dispersion signatures within each auroral ray can be analyzed in detail during a fraction of a second. The evolution of energy and flux of the precipitation shows precipitation spanning over a large range of energies, with the characteristic energy dropping from 2.1 keV to 0.87 keV over 0.2 s. Oscillations at 2.4 Hz in the magnetic zenith correspond to the period of the auroral flames, and the acceleration is believed to be due to Alfvenic wave interaction with electrons above the ionosphere.

  9. Drift velocities of 150-km Field-Aligned Irregularities observed by the Equatorial Atmosphere Radar

    Directory of Open Access Journals (Sweden)

    Yuichi Otsuka

    2013-11-01

    Full Text Available Between 130 and 170 km altitude in the daytime ionosphere, the so-called 150-km field-aligned irregularities (FAIs have been observed since the 1960s at equatorial regions with several very high frequency (VHF radars. We report statistical results of 150-km FAI drift velocities on a plane perpendicular to the geomagnetic field, acquired by analyzing the Doppler velocities of 150-km FAIs observed with the Equatorial Atmosphere Radar (EAR at Kototabang, Indonesia during the period from Aug. 2007 to Oct. 2009. We found that the southward/upward perpendicular drift velocity of the 150-km FAIs tends to decrease in the afternoon and that this feature is consistent with that of F-region plasma drift velocities over the magnetic equator. The zonal component of the 150-km FAI drift velocity is westward and decreases with time, whereas the F-region plasma drift velocity observed with the incoherent scatter radar at Jicamarca, Peru, which is westward, reaches a maximum at about noon. The southward/upward and zonal drift velocities of the 150-km FAIs are smaller than that of the F-region plasma drift velocity by approximately 3 m/s and 25 m/s, respectively, on average. The large difference between the 150-km FAI and F-region plasma drift velocities may not arise from a difference in the magnetic latitudes at which their electric fields are generated. Electric fields generated at the altitude at which the 150-km FAIs occur may not be negligible.

  10. The magnetized electron-acoustic instability driven by a warm, field-aligned electron beam

    International Nuclear Information System (INIS)

    Sooklal, A.; Mace, R.L.

    2004-01-01

    The electron-acoustic instability in a magnetized plasma having three electron components, one of which is a field-aligned beam of intermediate temperature, is investigated. When the plasma frequency of the cool electrons exceeds the electron gyrofrequency, the electron-acoustic instability 'bifurcates' at sufficiently large propagation angles with respect to the magnetic field to yield an obliquely propagating, low-frequency electron-acoustic instability and a higher frequency cyclotron-sound instability. Each of these instabilities retains certain wave features of its progenitor, the quasiparallel electron-acoustic instability, but displays also new magnetic qualities through its dependence on the electron gyrofrequency. The obliquely propagating electron-acoustic instability requires a lower threshold beam speed for its excitation than does the cyclotron-sound instability, and for low to intermediate beam speeds has the higher maximum growth rate. When the plasma is sufficiently strongly magnetized that the plasma frequency of the cool electrons is less than the electron gyrofrequency, the only instability in the electron-acoustic frequency range is the strongly magnetized electron-acoustic instability. Its growth rate and real frequency exhibit a monotonic decrease with wave propagation angle and it grows at small to intermediate wave numbers where its parallel phase speed is approximately constant. The relevance of the results to the interpretation of cusp auroral hiss and auroral broadband electrostatic noise is briefly discussed

  11. Characteristics of electron cyclotron waves creating field-aligned and transverse plasma-potential structures

    International Nuclear Information System (INIS)

    Takahashi, K; Kaneko, T; Hatakeyama, R; Fukuyama, A

    2009-01-01

    Characteristics of electromagnetic waves of azimuthal mode number m = ±1 are investigated experimentally, analytically and numerically when the waves triggering the field-aligned and transverse plasma-potential structure modification near an electron cyclotron resonance (ECR) point are injected into an inhomogeneously magnetized plasma with high-speed ion flow. The waves of m = +1 and -1 modes generate an electric double layer near the ECR point at the radially central and peripheral areas of the plasma column, respectively, and the transverse electric fields are consequently formed. At these areas the waves have a right-handed polarization and are absorbed through the ECR mechanism, where the experimental and analytical results do show the polarization reversal along the radial axis. The numerical results by plasma analysis by finite element method (FEM)/wave analysis by FEM (PAF/WF) code show that the wave-absorption area is localized at the radially central and peripheral areas for m = +1 and -1 mode waves, respectively, being consistent with the experimental and analytical ones.

  12. Label-Free Alignment of Nonmagnetic Particles in a Small Uniform Magnetic Field.

    Science.gov (United States)

    Wang, Zhaomeng; Wang, Ying; Wu, Rui Ge; Wang, Z P; Ramanujan, R V

    2018-01-01

    Label-free manipulation of biological entities can minimize damage, increase viability and improve efficiency of subsequent analysis. Understanding the mechanism of interaction between magnetic and nonmagnetic particles in an inverse ferrofluid can provide a mechanism of label-free manipulation of such entities in a uniform magnetic field. The magnetic force, induced by relative magnetic susceptibility difference between nonmagnetic particles and surrounding magnetic particles as well as particle-particle interaction were studied. Label-free alignment of nonmagnetic particles can be achieved by higher magnetic field strength (Ba), smaller particle spacing (R), larger particle size (rp1), and higher relative magnetic permeability difference between particle and the surrounding fluid (Rμr). Rμr can be used to predict the direction of the magnetic force between both magnetic and nonmagnetic particles. A sandwich structure, containing alternate layers of magnetic and nonmagnetic particle chains, was studied. This work can be used for manipulation of nonmagnetic particles in lab-on-a-chip applications.

  13. Radar observations of field-aligned plasma irregularities in the SEEK-2 campaign

    Directory of Open Access Journals (Sweden)

    S. Saito

    2005-10-01

    Full Text Available During the Sporadic E Experiment over Kyushu 2 (SEEK-2 campaign, field-aligned irregularities (FAIs associated with midlatitude sporadic-E (Es layers were observed with two backscatter radars, the Lower Thermosphere Profiler Radar (LTPR and the Frequency Agile Radar (FAR, which were located 40 km apart in Tanegashima, Japan. We conducted observations of FAI echoes from 31 July to 24 August 2002, and the radar data were used to determine launch timing of two sounding rockets on 3 August 2002. Our comparison of echoes obtained by the LTPR and the FAR revealed that echoes often appeared at the FAR about 10min earlier than they did at the LTPR and were well correlated. This indicates that echoing regions drift with a southward velocity component that maintains the spatial shape. Interferometry observations that were conducted with the LTPR from 3 to 8 August 2002, revealed that the quasi-periodic (QP striations in the Range-Time-Intensity (RTI plots were due to the apparent motion of echoing regions across the radar beam including both main and side lobes. In most cases, the echo moved to the east-southeast at an almost constant altitude of 100–110 km, which was along the locus of perpendicularity of the radar line-of-sight to the geomagnetic field line. We found that the QP pattern on the RTI plot reflects the horizontal structure and motion of the (Es layer, and that echoing regions seemed to be in one-dimensionally elongated shapes or in chains of patches. Neutral wind velocities from 75 to 105 km altitude were simultaneously derived with meteor echoes from the LTPR. This is the first time-continuous simultaneous observation FAIs and neutral wind with interferometry measurements. Assuming that the echoing regions were drifting with an ambient neutral wind, we found that the echoing region was aligned east-northeast-west-southwest in eight out of ten QP echo events during the SEEK-2 campaign. A range rate was

  14. Fan texture of the compound Ba3Co2Fe244O41 pre-aligned in a magnetic field

    NARCIS (Netherlands)

    Huijser-Gerits, E.M.C.; Rieck, G.D.; Vogel, D.L.

    1970-01-01

    Samples of the ferrimagnetic material Ba3Co2Fe24O41, pre-aligned in a magnetic field and sintered at various temps., have been examd. for preferred orientation. Schulz's reflection technique and the standardizing method of Holland were used to det. quant. pole figures of several lattice planes. The

  15. Field-aligned structure of the storm time Pc 5 wave of November 14-15, 1979

    International Nuclear Information System (INIS)

    Takahashi, K.; Higbie, P.R.; Fennell, J.F.; Amata, E.

    1987-01-01

    Magnetic field data from the four satellites SCATHA (P78-2), GOES 2, GOES 3, and GEOS 2 have been analyzed to examine the magnetic field-aligned structure of a storm time Pc 5 wave that occurred on November 14-15, 1979. The wave had both transverse and compressional components. At a given instance the compressional and the radial components oscillated in phase of 180 degree out of phase, and the compressional and the azimuthal components oscillated +90 degree or -90 degree out of phase. In addition, each component changed its amplitude with magnetic latitude: the compressional component had a minimum at the magnetic equator, whereas the transverse components had a maximum at the equator and minima several degrees off the equator. A 180 degree relative phase switching among the components occurred across the latitudes of amplitude minima. From these observations the field line displacement of the wave is confirmed to have an antisymmetric standing structure about the magnetic equator with a parallel wave length of a few earth radii. The authors also observed other intriguing properties of the wave such as different parallel wave lengths of different field components and small-amplitude second harmonics near the nodes. A dielectric tensor appropriate for the ring current plasma is found to give an explanation for the relation between the polarization and the propagation of the wave. However, plasma data available from SCATHA does not support either the drift mirror instability of A. Hasegawa (1969) or the coupling between a drift mirror wave and a shear Alfven wave as discussed by A.D.M. Walker et al. (1982)

  16. Computer-simulation movie of ionospheric electric fields and currents for a magnetospheric substorm life cycle. Technical note

    International Nuclear Information System (INIS)

    Kamide, Y.; Matsushita, S.

    1980-07-01

    Numerical solution of the current conservation equation gives the distributions of electric fields and currents in the global ionosphere produced by the field-aligned currents. By altering ionospheric conductivity distributions as well as the field-aligned current densities and configurations to simulate a magnetospheric substorm life cycle, which is assumed to last for five hours, various patterns of electric fields and currents are computed for every 30-second interval in the life cycle. The simulated results are compiled in the form of a color movie, where variations of electric equi-potential curves are the first sequence, electric current-vector changes are the second, and fluctuations of the electric current system are the third. The movie compresses real time by a factor of 1/180, taking 1.7 minutes of running time for one sequence. One of the most striking features of this simulation is the clear demonstration of rapid and large scale interactions between the auroral zone and middle-low latitudes during the substorm sequences. This technical note provides an outline of the numerical scheme and world-wide contour maps of the electric potential, ionospheric current vectors, and the equivalent ionospheric current system at 5-minute intervals as an aid in viewing the movie and to further detailed study of the 'model' substorms

  17. Alfven-wave current drive and magnetic field stochasticity

    International Nuclear Information System (INIS)

    Litwin, C.; Hegna, C.C.

    1993-01-01

    Propagating Alfven waves can generate parallel current through an alpha effect. In resistive MHD however, the dynamo field is proportional to resistivity and as such cannot drive significant currents for realistic parameters. In the search for an enhancement of this effect the authors investigate the role of magnetic field stochasticity. They show that the presence of a stochastic magnetic field, either spontaneously generated by instabilities or induced externally, can enhance the alpha effect of the wave. This enhancement is caused by an increased wave dissipation due to both current diffusion and filamentation. For the range of parameters of current drive experiments at Phaedrus-T tokamak, a moderate field stochasticity leads to significant modifications in the loop voltage

  18. Polarization properties of below-threshold harmonics from aligned molecules H2+ in linearly polarized laser fields.

    Science.gov (United States)

    Dong, Fulong; Tian, Yiqun; Yu, Shujuan; Wang, Shang; Yang, Shiping; Chen, Yanjun

    2015-07-13

    We investigate the polarization properties of below-threshold harmonics from aligned molecules in linearly polarized laser fields numerically and analytically. We focus on lower-order harmonics (LOHs). Our simulations show that the ellipticity of below-threshold LOHs depends strongly on the orientation angle and differs significantly for different harmonic orders. Our analysis reveals that this LOH ellipticity is closely associated with resonance effects and the axis symmetry of the molecule. These results shed light on the complex generation mechanism of below-threshold harmonics from aligned molecules.

  19. Shocklets, SLAMS, and Field-Aligned Ion Beams in the Terrestrial Foreshock

    Science.gov (United States)

    Wilson, L. B.; Koval, A.; Sibeck, D. G.; Szabo, A.; Cattell, C. A.; Kasper, J. C.; Maruca, B. A.; Pulupa, M.; Salem, C. S.; Wilber, M.

    2012-01-01

    We present Wind spacecraft observations of ion distributions showing field- aligned beams (FABs) and large-amplitude magnetic fluctuations composed of a series of shocklets and short large-amplitude magnetic structures (SLAMS). The FABs are found to have T(sub k) approx 80-850 eV, V(sub b)/V(sub sw) approx 1.3-2.4, T(sub perpendicular,b)/T(sub paralell,b) approx 1-8, and n(sub b)/n(sub o) approx 0.2-11%. Saturation amplitudes for ion/ion resonant and non-resonant instabilities are too small to explain the observed SLAMS amplitudes. We show two examples where groups of SLAMS can act like a local quasi-perpendicular shock reflecting ions to produce the FABs, a scenario distinct from the more-common production at the quasi-perpendicular bow shock. The SLAMS exhibit a foot-like magnetic enhancement with a leading magnetosonic whistler train, consistent with previous observations. Strong ion and electron heating are observed within the series of shocklets and SLAMS with temperatures increasing by factors approx > 5 and approx >3, respectively. Both the core and halo electron components show strong perpendicular heating inside the feature.

  20. Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields

    Energy Technology Data Exchange (ETDEWEB)

    Armas-Pérez, Julio C.; Londono-Hurtado, Alejandro [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Guzmán, Orlando [Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, DF 09340, México (Mexico); Hernández-Ortiz, Juan P. [Departamento de Materiales y Minerales, Universidad Nacional de Colombia, Sede Medellín, Medellín (Colombia); Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Pablo, Juan J. de, E-mail: depablo@uchicago.edu [Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2015-07-28

    A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

  1. Theoretically informed Monte Carlo simulation of liquid crystals by sampling of alignment-tensor fields.

    Energy Technology Data Exchange (ETDEWEB)

    Armas-Perez, Julio C.; Londono-Hurtado, Alejandro; Guzman, Orlando; Hernandez-Ortiz, Juan P.; de Pablo, Juan J.

    2015-07-27

    A theoretically informed coarse-grained Monte Carlo method is proposed for studying liquid crystals. The free energy functional of the system is described in the framework of the Landau-de Gennes formalism. The alignment field and its gradients are approximated by finite differences, and the free energy is minimized through a stochastic sampling technique. The validity of the proposed method is established by comparing the results of the proposed approach to those of traditional free energy minimization techniques. Its usefulness is illustrated in the context of three systems, namely, a nematic liquid crystal confined in a slit channel, a nematic liquid crystal droplet, and a chiral liquid crystal in the bulk. It is found that for systems that exhibit multiple metastable morphologies, the proposed Monte Carlo method is generally able to identify lower free energy states that are often missed by traditional approaches. Importantly, the Monte Carlo method identifies such states from random initial configurations, thereby obviating the need for educated initial guesses that can be difficult to formulate.

  2. 30 MHz radar observations of artificial E region field-aligned plasma irregularities

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2008-02-01

    Full Text Available Artificial E region field aligned irregularities (FAIs have been observed during heating experiments at the HAARP facility using a new 30 MHz coherent scatter radar imager deployed near Homer, Alaska. Irregularities were observed during brief experiments on three quiet days in July and August, 2007, when the daytime E region critical frequency was close to 3 MHz. Irregularities were consistently generated and detected during experiments with O-mode HF pumping on zenith with a 1-min on, 1-min off CW modulation. The scattering cross sections, rise, and fall times of the echoes were observed as well as their spectral properties. Results were found to be mainly in agreement with observations from other mid- and high-latitude sites with some discrepancies. Radar images of the irregularity-filled volume on one case exhibited clear variations in backscatter power and Doppler shift across the volume. The images furthermore show the emergence of a small irregularity-filled region to the south southwest of the main region in the approximate direction of magnetic zenith.

  3. The LACARA Vacuum Laser Accelerator Experiment: Beam Positioning and Alignment in a Strong Magnetic Field

    International Nuclear Information System (INIS)

    Shchelkunov, Sergey V.; Marshall, T. C.; Hirshfield, J. L.; Wang, Changbiao; LaPointe, M. A.

    2006-01-01

    LACARA (laser cyclotron auto-resonance accelerator) is a vacuum laser accelerator of electrons that is under construction at the Accelerator Test Facility (ATF), Brookhaven National Laboratory. It is expected that the experiment will be assembled by September 2006; this paper presents progress towards this goal. According to numerical studies, as an electron bunch moves along the LACARA solenoidal magnetic field (∼5.2 T, length ∼1 m), it will be accelerated from 50 to ∼75 MeV by interacting with a 0.8 TW Gaussian-mode circularly polarized optical pulse provided by the ATF CO2 10.6μm laser system. The LACARA laser transport optics must handle 10 J and be capable of forming a Gaussian beam inside the solenoid with a 1.4 mm waist and a Rayleigh range of 60 cm. The electron optics must transport a bunch having input emittance of 0.015 mm-mrad and 100 μm waist through the magnet. Precision alignment between the electron beam and the solenoid magnetic axis is required, and a method to achieve this is described in detail. Emittance- filtering may be necessary to yield an accelerated bunch having a narrow (∼1%) energy-spread

  4. Effect of field-aligned-beam in parallel diffusion of energetic particles in the Earth's foreshock

    Science.gov (United States)

    Matsukiyo, S.; Nakanishi, K.; Otsuka, F.; Kis, A.; Lemperger, I.; Hada, T.

    2016-12-01

    Diffusive shock acceleration (DSA) is one of the plausible acceleration mechanisms of cosmic rays. In the standard DSA model the partial density of the accelerated particles, diffused into upstream, exponentially decreases as the distance to the shock increases. Kis et al. (GRL, 31, L20801, 2004) examined the density gradients of energetic ions upstream of the bow shock with high accuracy by using Cluster data. They estimated the diffusion coefficients of energetic ions for the event in February 18, 2003 and showed that the obtained diffusion coefficients are significantly smaller than those estimated in the past statistical study. This implies that particle acceleration at the bow shock can be more efficient than considered before. Here, we focus on the effect of the field-aligned-beam (FAB) which is often observed in the foreshock, and examine how the FAB affects the efficiency of diffusion of the energetic ions by performing test particle simulations. The upstream turbulence is given by the superposition of parallel Alfven waves with power-law energy spectrum with random phase approximation. In the spectrum we further add a peak corresponding to the waves resonantly generated by the FAB. The dependence of the diffusion coefficient on the presence of the FAB as well as total energy of the turbulence, power-law index of the turbulence, and intensity of FAB oriented waves are discussed.

  5. Streaming current magnetic fields in a charged nanopore

    Science.gov (United States)

    Mansouri, Abraham; Taheri, Peyman; Kostiuk, Larry W.

    2016-01-01

    Magnetic fields induced by currents created in pressure driven flows inside a solid-state charged nanopore were modeled by numerically solving a system of steady state continuum partial differential equations, i.e., Poisson, Nernst-Planck, Ampere and Navier-Stokes equations (PNPANS). This analysis was based on non-dimensional transport governing equations that were scaled using Debye length as the characteristic length scale, and applied to a finite length cylindrical nano-channel. The comparison of numerical and analytical studies shows an excellent agreement and verified the magnetic fields density both inside and outside the nanopore. The radially non-uniform currents resulted in highly non-uniform magnetic fields within the nanopore that decay as 1/r outside the nanopore. It is worth noting that for either streaming currents or streaming potential cases, the maximum magnetic field occurred inside the pore in the vicinity of nanopore wall, as opposed to a cylindrical conductor that carries a steady electric current where the maximum magnetic fields occur at the perimeter of conductor. Based on these results, it is suggested and envisaged that non-invasive external magnetic fields readouts generated by streaming/ionic currents may be viewed as secondary electronic signatures of biomolecules to complement and enhance current DNA nanopore sequencing techniques. PMID:27833119

  6. Magneto-plasmonic study of aligned Ni, Co and Ni/Co multilayer in polydimethylsiloxane as magnetic field sensor

    Energy Technology Data Exchange (ETDEWEB)

    Hamidi, Seyedeh Mehri, E-mail: M_hamidi@sbu.ac.ir [Magneto-plasmonic Lab, Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Mosaeii, Babak; Afsharnia, Mina [Magneto-plasmonic Lab, Laser and Plasma Research Institute, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Aftabi, Ali [Physics Department, Shahid Beheshti University, Tehran (Iran, Islamic Republic of); Najafi, Mojgan [Department of Materials Engineering, Hamedan University of Technology, Hamedan (Iran, Islamic Republic of)

    2016-11-01

    We report the magneto-optical properties of aligned cobalt, Nickel and nickel/ Cobalt multilayer nanowires embedded in polydimethylsiloxane matrix. The NWs prepared by electrodeposition method in anodic alumina template and then dispersed in ethanol and placed in a heater to evaporate the ethanol and finally dispersed in polydimethylsiloxane matrix to reach to the composite. The used external magnetic field arranges the nanowires and our aligned nanowires were investigated by magneto-optical surface plasmon resonance techniques in two easy and hard axis configurations. Our results show the sufficient sensitivity in magneto-optical surface plasmon resonance of Nickel and cobalt arrays nanowires and because the different modulation mechanism in Ni and Co nanodisks, in Ni/Co multilayer we see the magnetization modulation of the excitation angle in accordance with magnetic field modulation of the SPP wave vector in each nanodisk. Finally, we show that the Ni/Co multilayer aligned nanowires can be used as efficient magnetic field sensor. - Highlights: • The magneto-optical properties of aligned multilayer nanowires has been investigated. • We see the sufficient sensitivity in magneto-optical surface plasmon resonance of Ni and Co nanowires. • The magnetic modulation mechanism in Ni/Co multilayer has been changed by angular modulation. • The magnetization modulation of the excitation angle accompanying the SPP wave vector modulation takes place in each nanodisk of multilayer.

  7. Role of adsorbates on current fluctuations in DC field emission

    International Nuclear Information System (INIS)

    Luong, M.; Bonin, B.; Long, H.; Safa, H.

    1996-01-01

    Field emission experiments in DC regime usually show important current fluctuations for a fixed electric field. These fluctuations are attributed to adsorbed layers (molecules or atoms), liable to affect the work function, height and shape of the potential barrier binding the electron in the metal. The role of these adsorbed species is investigated by showing that the field emission from a well desorbed sample is stable and reproducible and by comparing the emission from the same sample before and after desorption. (author)

  8. Geometric accuracy of field alignment in fractionated stereotactic conformal radiotherapy of brain tumors

    International Nuclear Information System (INIS)

    Kortmann, Rolf D.; Becker, Gerd; Perelmouter, Jury; Buchgeister, Markus; Meisner, Christoph; Bamberg, Michael

    1999-01-01

    Purpose: To assess the accuracy of field alignment in patients undergoing three-dimensional (3D) conformal radiotherapy of brain tumors, and to evaluate the impact on the definition of planning target volume and control procedures. Methods and Materials: Geometric accuracy was analyzed in 20 patients undergoing fractionated stereotactic conformal radiotherapy for brain tumors. Rigid head fixation was achieved by using cast material. Transfer of stereotactic coordinates was performed by an external positioning device. The accuracy during treatment planning was quantitatively assessed by using repeated computed tomography (CT) examinations in treatment position (reproducibility of isocenter). Linear discrepancies were measured between treatment plan and CT examination. In addition, for each patient, a series of 20 verifications were taken in orthogonal projections. Linear discrepancies were measured between first and all subsequent verifications (accuracy during treatment delivery). Results: For the total group of patients, the distribution of deviations during treatment setup showed mean values between -0.3-1.2 mm, with standard deviations (SD) of 1.3-2.0 mm. During treatment delivery, the distribution of deviations revealed mean values between 0.7-0.8 mm, with SDs of 0.5-0.6 mm, respectively. For all patients, deviations for the transition to the treatment machine were similar to deviations during subsequent treatment delivery, with 95% of all absolute deviations between less than 2.8 and 4.6 mm. Conclusion: Random fluctuations of field displacements during treatment planning and delivery prevail. Therefore, our quantitative data should be considered when prescribing the safety margins of the planning target volume. Repeated CT examination are useful to detect operator errors and large random or systematic deviations before start of treatment. Control procedures during treatment delivery appear to be of limited importance. In addition, our findings should help to

  9. Field and current amplification in the SSPX spheromak

    International Nuclear Information System (INIS)

    Hill, D.N. . hilld@llnl.gov; Bulmer, R.H.; Cohen, B.I.

    2003-01-01

    Results are presented from experiments relating to magnetic field generation and current amplification in the SSPX spheromak. The SSPX spheromak plasma is driven by DC coaxial helicity injection using a 2MJ capacitor bank. Peak toroidal plasma currents of up to 0.7MA and peak edge poloidal fields of 0.3T are produced; lower current discharges can be sustained up to 3.5msec. When edge magnetic fluctuations are reduced below 1% by driving the plasma near threshold, it is possible to produce plasmas with Te > 150eV, e >∼4% and core χ e ∼30m 2 /s. Helicity balance for these plasmas suggests that sheath dissipation can be significant, pointing to the importance of maximizing the voltage on the coaxial injector. For most operational modes we find a stiff relationship between peak spheromak field and injector current, and little correlation with plasma temperature, which suggests that other processes than ohmic dissipation may limit field amplification. However, slowing spheromak buildup by limiting the initial current pulse increases the ratio of toroidal current to injected current and points to new operating regimes with more favorable current amplification. (author)

  10. Steady electric fields and currents elementary electromagnetic theory

    CERN Document Server

    Chirgwin, B H; Kilmister, C W

    2013-01-01

    Steady Electric Fields and Currents, Volume 1 is an introductory text to electromagnetism and potential theory. This book starts with the fields associated with stationary charges and unravels the stationary condition to allow consideration of the flow of steady currents in closed circuits. The opening chapter discusses the experimental results that require mathematical explanation and discussion, particularly those referring to phenomena that question the validity of the simple Newtonian concepts of space and time. The subsequent chapters consider steady-state fields, electrostatics, dielectr

  11. Electric fields and monopole currents in compact QED

    International Nuclear Information System (INIS)

    Zach, M.; Faber, M.; Kainz, W.; Skala, P.

    1995-01-01

    The confinement in compact QED is known to be related to magnetic monopoles. Magnetic currents form a solenoid around electric flux lines between a pair of electric charges. This behaviour can be described by the dual version of Maxwell-London equations including a fluctuating string. We use a definition of magnetic monopole currents adjusted to the definition of the electric field strength on a lattice and get good agreement for field and current distributions between compact QED and the predictions of dual Maxwell-London equations. Further we show that the monopole fluctuations in the vacuum are suppressed by the flux tube. ((orig.))

  12. Stellarator fields with small PS current at small rotational transform

    International Nuclear Information System (INIS)

    Herrnegger, F.

    2001-01-01

    One aspect of the optimization concept of stellarators is the reduction of the normalized Pfirsch-Schlueter current density p arallel 2 / j p erpendikular 2 > 1/2 to a reasonable level but obeying other side conditions, e.g., concerning small bootstrap currents, good stability properties, reasonable aspect ratio, etc. This problem is addressed in the present work. Various stellarator vacuum field are given analytically for M 2, 3, 5, 10, 12 (M is the number of field period around the torus) where the PS-current density is reduced by more than a factor of ten to rather small values around 0.3 even at small i-values

  13. Determinants of the electric field during transcranial direct current stimulation

    DEFF Research Database (Denmark)

    Opitz, Alexander; Paulus, Walter; Will, Susanne

    2015-01-01

    Transcranial direct current stimulation (tDCS) causes a complex spatial distribution of the electric current flow in the head which hampers the accurate localization of the stimulated brain areas. In this study we show how various anatomical features systematically shape the electric field...... over the motor cortex in small steps to examine the resulting changes of the electric field distribution in the underlying cortex. We examined the effect of skull thickness and composition on the passing currents showing that thinner skull regions lead to higher electric field strengths. This effect...... fluid and the skull, the gyral depth and the distance to the anode and cathode. These factors account for up to 50% of the spatial variation of the electric field strength. Further, we demonstrate that individual anatomical factors can lead to stimulation "hotspots" which are partly resistant...

  14. Time development of electric fields and currents in space plasmas

    Directory of Open Access Journals (Sweden)

    A. T. Y. Lui

    2006-05-01

    Full Text Available Two different approaches, referred to as Bu and Ej, can be used to examine the time development of electric fields and currents in space plasmas based on the fundamental laws of physics. From the Bu approach, the required equation involves the generalized Ohm's law with some simplifying assumptions. From the Ej approach, the required equation can be derived from the equation of particle motion, coupled self-consistently with Maxwell's equation, and the definition of electric current density. Recently, some strong statements against the Ej approach have been made. In this paper, we evaluate these statements by discussing (1 some limitations of the Bu approach in solving the time development of electric fields and currents, (2 the procedure in calculating self-consistently the time development of the electric current in space plasmas without taking the curl of the magnetic field in some cases, and (3 the dependency of the time development of magnetic field on electric current. It is concluded that the Ej approach can be useful to understand some magnetospheric problems. In particular, statements about the change of electric current are valid theoretical explanations of change in magnetic field during substorms.

  15. Self-propelled in-tube shuttle and control system for automated measurements of magnetic field alignment

    International Nuclear Information System (INIS)

    Boroski, W.N.; Nicol, T.H.; Pidcoe, S.V.

    1990-03-01

    A magnetic field alignment gauge is used to measure the field angle as a function of axial position in each of the magnets for the Superconducting Super Collider (SSC). Present measurements are made by manually pushing the through the magnet bore tube and stopping at intervals to record field measurements. Gauge location is controlled through graduation marks and alignment pins on the push rods. Field measurements are recorded on a logging multimeter with tape output. Described is a computerized control system being developed to replace the manual procedure for field alignment measurements. The automated system employs a pneumatic walking device to move the measurement gauge through the bore tube. Movement of the device, called the Self-Propelled In-Tube Shuttle (SPITS), is accomplished through an integral, gas driven, double-acting cylinder. The motion of the SPITS is transferred to the bore tube by means of a pair of controlled, retractable support feet. Control of the SPITS is accomplished through an RS-422 interface from an IBM-compatible computer to a series of solenoid-actuated air valves. Direction of SPITS travel is determined by the air-valve sequence, and is managed through the control software. Precise axial position of the gauge within the magnet is returned to the control system through an optically-encoded digital position transducer attached to the shuttle. Discussed is the performance of the transport device and control system during preliminary testing of the first prototype shuttle. 1 ref., 7 figs

  16. Rf Gun with High-Current Density Field Emission Cathode

    International Nuclear Information System (INIS)

    Jay L. Hirshfield

    2005-01-01

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  17. Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations

    Directory of Open Access Journals (Sweden)

    J. S. de Villiers

    2014-10-01

    Full Text Available This research focuses on the inversion of geomagnetic variation field measurement to obtain source currents in the ionosphere. During a geomagnetic disturbance, the ionospheric currents create magnetic field variations that induce geoelectric fields, which drive geomagnetically induced currents (GIC in power systems. These GIC may disturb the operation of power systems and cause damage to grounded power transformers. The geoelectric fields at any location of interest can be determined from the source currents in the ionosphere through a solution of the forward problem. Line currents running east–west along given surface position are postulated to exist at a certain height above the Earth's surface. This physical arrangement results in the fields on the ground having the magnetic north and down components, and the electric east component. Ionospheric currents are modelled by inverting Fourier integrals (over the wavenumber of elementary geomagnetic fields using the Levenberg–Marquardt technique. The output parameters of the inversion model are the current strength, height and surface position of the ionospheric current system. A ground conductivity structure with five layers from Quebec, Canada, based on the Layered-Earth model is used to obtain the complex skin depth at a given angular frequency. This paper presents preliminary and inversion results based on these structures and simulated geomagnetic fields. The results show some interesting features in the frequency domain. Model parameters obtained through inversion are within 2% of simulated values. This technique has applications for modelling the currents of electrojets at the equator and auroral regions, as well as currents in the magnetosphere.

  18. Analysis of the Numerical Diffusion in Anisotropic Mediums: Benchmarks for Magnetic Field Aligned Meshes in Space Propulsion Simulations

    Directory of Open Access Journals (Sweden)

    Daniel Pérez-Grande

    2016-11-01

    Full Text Available This manuscript explores numerical errors in highly anisotropic diffusion problems. First, the paper addresses the use of regular structured meshes in numerical solutions versus meshes aligned with the preferential directions of the problem. Numerical diffusion in structured meshes is quantified by solving the classical anisotropic diffusion problem; the analysis is exemplified with the application to a numerical model of conducting fluids under magnetic confinement, where rates of transport in directions parallel and perpendicular to a magnetic field are quite different. Numerical diffusion errors in this problem promote the use of magnetic field aligned meshes (MFAM. The generation of this type of meshes presents some challenges; several meshing strategies are implemented and analyzed in order to provide insight into achieving acceptable mesh regularity. Second, Gradient Reconstruction methods for magnetically aligned meshes are addressed and numerical errors are compared for the structured and magnetically aligned meshes. It is concluded that using the latter provides a more correct and straightforward approach to solving problems where anisotropicity is present, especially, if the anisotropicity level is high or difficult to quantify. The conclusions of the study may be extrapolated to the study of anisotropic flows different from conducting fluids.

  19. Accessing the molecular frame through strong-field alignment of distributions of gas phase molecules

    Science.gov (United States)

    Reid, Katharine L.

    2018-03-01

    A rationale for creating highly aligned distributions of molecules is that it enables vector properties referenced to molecule-fixed axes (the molecular frame) to be determined. In the present work, the degree of alignment that is necessary for this to be achieved in practice is explored. Alignment is commonly parametrized in experiments by a single parameter, ?, which is insufficient to enable predictive calculations to be performed. Here, it is shown that, if the full distribution of molecular axes takes a Gaussian form, this single parameter can be used to determine the complete set of alignment moments needed to characterize the distribution. In order to demonstrate the degree of alignment that is required to approach the molecular frame, the alignment moments corresponding to a few chosen values of ? are used to project a model molecular frame photoelectron angular distribution into the laboratory frame. These calculations show that ? needs to approach 0.9 in order to avoid significant blurring to be caused by averaging. This article is part of the theme issue `Modern theoretical chemistry'.

  20. Galaxy Alignments: Theory, Modelling & Simulations

    Science.gov (United States)

    Kiessling, Alina; Cacciato, Marcello; Joachimi, Benjamin; Kirk, Donnacha; Kitching, Thomas D.; Leonard, Adrienne; Mandelbaum, Rachel; Schäfer, Björn Malte; Sifón, Cristóbal; Brown, Michael L.; Rassat, Anais

    2015-11-01

    The shapes of galaxies are not randomly oriented on the sky. During the galaxy formation and evolution process, environment has a strong influence, as tidal gravitational fields in the large-scale structure tend to align nearby galaxies. Additionally, events such as galaxy mergers affect the relative alignments of both the shapes and angular momenta of galaxies throughout their history. These "intrinsic galaxy alignments" are known to exist, but are still poorly understood. This review will offer a pedagogical introduction to the current theories that describe intrinsic galaxy alignments, including the apparent difference in intrinsic alignment between early- and late-type galaxies and the latest efforts to model them analytically. It will then describe the ongoing efforts to simulate intrinsic alignments using both N-body and hydrodynamic simulations. Due to the relative youth of this field, there is still much to be done to understand intrinsic galaxy alignments and this review summarises the current state of the field, providing a solid basis for future work.

  1. Off-great-circle paths in transequatorial propagation: 2. Nonmagnetic-field-aligned reflections

    Science.gov (United States)

    Tsunoda, Roland T.; Maruyama, Takashi; Tsugawa, Takuya; Yokoyama, Tatsuhiro; Ishii, Mamoru; Nguyen, Trang T.; Ogawa, Tadahiko; Nishioka, Michi

    2016-11-01

    There is considerable evidence that plasma structure in nighttime equatorial F layer develops from large-scale wave structure (LSWS) in bottomside F layer. However, crucial details of how this process proceeds, from LSWS to equatorial plasma bubbles (EPBs), remain to be sorted out. A major obstacle to success is the paucity of measurements that provide a space-time description of the bottomside F layer over a broad geographical region. The transequatorial propagation (TEP) experiment is one of few methods that can do so. New findings using a TEP experiment, between Shepparton (SHP), Australia, and Oarai (ORI), Japan, are presented in two companion papers. In Paper 1 (P1), (1) off-great-circle (OGC) paths are described in terms of discrete and diffuse types, (2) descriptions of OGC paths are generalized from a single-reflection to a multiple-reflection process, and (3) discrete type is shown to be associated with an unstructured but distorted upwelling, whereas the diffuse type is shown to be associated with EPBs. In Paper 2 (P2), attention is placed on differences in east-west (EW) asymmetry, found between OGC paths from the SHP-ORI experiment and those from another near-identical TEP experiment. Differences are reconciled by allowing three distinct sources for the EW asymmetries: (1) reflection properties within an upwelling (see P1), (2) OGC paths that depend on magnetic declination of geomagnetic field (B), and (3) OGC paths supported by non-B-aligned reflectors at latitudes where inclination of B is finite.

  2. Investigation on the relationship among sporadic Na, sporadic E, Field aligned irregularities and neutral winds

    Science.gov (United States)

    Sundararajan, Sridharan; Patra, Amit Kumar; Pant, Tarun; Gurubaran, Subramanian; Raghunath, Karnam

    In the Mesosphere and Lower Thermosphere region (80-100 km), metallic atoms, namely, sodium, potassium, lithium, Iron etc are formed due to ablation of meteors. The lidars based on resonance fluorescence principle has been used to study the vertical distribution of sodium atoms, because of their large abundance than other metals. The profiles of sodium density sometimes show enhancement by a factor of 2 than the normal layer in a narrow altitude region of 2 km and on these occasions, they are called sporadic sodium layer, or briefly Ns. On the other hand, there are observations on sporadic E and radar observations of Field Aligned Irregularities (FAI) associated with these sporadic E. Some investigations have been made to understand the relationship between sporadic E and FAI. Considering that sporadic E is composed of metallic ions and the time of metallic ions are larger compared to other ions, the sodium observations in the same height region would be of significant importance to understand the process involved. Despite a few past observations, no clear picture has emerged due to lack of simultaneous measurements of these parameters. The simultaneous observations of FAI echoes by the Indian MST radar and sodium concentration by the sodium lidar at Gadanki (13.5o N, 79.2o E) are being used to investigate the above mentioned relationship. The Sporadic E and neutral wind information are obtained from the ionosonde, meteor/MF radar observations from Trivandrum (8.5o N, 77E) and Tirunelveli (8.7o N, 77.8o E). The results obtained will be presented during the meeting.

  3. Current-current correlation function in presence of chemical potential and external magnetic field

    International Nuclear Information System (INIS)

    Apresyan, E.A.

    2017-01-01

    The (2+1)-dimensional electron system was observed, where relation between the Green functions and conductivity was used. The current-current correlation function Π_μ_ν(B) for the fermion system was calculated in presence of non-quantizing magnetic field B, chemical potential η and gap m. From this function it is possible to obtain the equation for polarization operator calculated without the magnetic field. The result is also applicable for graphene

  4. Galactic cosmic ray gradients, field-aligned and latitudinal, among Voyagers 1/2 and IMP-8

    International Nuclear Information System (INIS)

    Roelof, E.C.; Decker, R.B.; Krimigis, S.M.; Venkatesan, D.; Lazarus, A.J.

    1982-01-01

    The tandem Earth-Jupiter trajectories of the Voyager 1/2 spacecraft, combined with baseline measurements from the earth-orbiting IMP-7/8 spacecraft, provide the first opportunity for unambiguously separating latitude from radial or field-aligned effects in galactic cosmic ray gradients. Anti-coincidence solid-state detectors on the Voyager 1/2 LECP experiment measure nucleons > or approximately 20 MeV/nuc with large (28 cm 2 ) omnidirectional geometry factors. Anti-coincidence scintillators on the IMP-7/8 CPME with omnidirectional geometry factors comparable to those on Voyager measure nucleons > or approximately 35 MeV/nuc. Because the Voyagers are well-connected via the interplanetary magnetic field (IMF) to the near-Earth vicinity throughout their transit from 1-5 AU (September 1977 - February 1979), we obtained the first direct measurement of field-aligned gradients, i.e., those that do not depend upon ''corotation'' from one spacecraft to another over many days. Another new result is the unambiguous identification of nonuniform latitudinal gradients approximately 2-5% degree -1 in structures lasting 10-30 days. There is additional evidence for somewhat smaller latitudinal gradients, north to south and probably mixed with small field-aligned gradients -1 , which persist for several solar rotations

  5. Fundamental properties of field emission-driven direct current microdischarges

    International Nuclear Information System (INIS)

    Rumbach, Paul; Go, David B.

    2012-01-01

    For half a century, it has been known that the onset of field emission in direct current microdischarges with gap sizes less than 10 μm can lead to breakdown at applied voltages far less than predicted by Paschen's law. It is still unclear how field emission affects other fundamental plasma properties at this scale. In this work, a one-dimensional fluid model is used to predict basic scaling laws for fundamental properties including ion density, electric field due to space charge, and current-voltage relations in the pre-breakdown regime. Computational results are compared with approximate analytic solutions. It is shown that field emission provides an abundance of cathode electrons, which in turn create large ion concentrations through ionizing collisions well before Paschen's criterion for breakdown is met. Breakdown due to ion-enhanced field emission occurs when the electric field due to space charge becomes comparable to the applied electric field. Simple scaling analysis of the 1D Poisson equation demonstrates that an ion density of n + ≈ 0.1V A ε 0 /qd 2 is necessary to significantly distort the electric field. Defining breakdown in terms of this critical ion density leads analytically to a simple, effective secondary emission coefficient γ ′ of the same mathematical form initially suggested by Boyle and Kisliuk [Phys. Rev. 97, 255 (1955)].

  6. Modeling the current distribution in HTS tapes with transport current and applied magnetic field

    NARCIS (Netherlands)

    Yazawa, T.; Yazawa, Takashi; Rabbers, J.J.; Chevtchenko, O.A.; ten Haken, Bernard; ten Kate, Herman H.J.; Maeda, Hideaki

    1999-01-01

    A numerical model is developed for the current distribution in a high temperature superconducting (HTS) tape, (Bi,Pb)2Sr2 Ca2Cu3Ox-Ag, subjected to a combination of a transport current and an applied magnetic field. This analysis is based on a two-dimensional formulation of Maxwell's equations in

  7. Field-controlled spin current in frustrated spin chains

    Directory of Open Access Journals (Sweden)

    A.K. Kolezhuk

    2009-01-01

    Full Text Available We study states with spontaneous spin current, emerging in frustrated antiferromagnetic spin-S chains subject to a strong external magnetic field. As a numerical tool, we use a non-Abelian symmetry realization of the density matrix renormalization group. The field dependence of the order parameter and the critical exponents are presented for zigzag chains with S=1/2, 1, 3/2, and 2.

  8. Structures of conserved currents and mass spectra for scalar fields

    International Nuclear Information System (INIS)

    Shintani, Meiun.

    1979-05-01

    Considering the commutators between a scalar field and a conserved current, we shall clarify the connection between the mass spectrum for a scalar field and the structures of a current. For a special form of currents involving c-number functions, non-invariance of the vacuum under the corresponding transformation entails the existence of a massive mode. It is shown that once a type of currents is specified, the pole structures for sub(o) depend only on c-number parts of J sub(μ)(x). We shall show that non-vanishing Goldstone commutator does not automatically imply the degeneracy of the vacuum state, and discuss the applicability of the Goldstone theorem. (author)

  9. Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

    International Nuclear Information System (INIS)

    Barth, Ingo; Smirnova, Olga

    2014-01-01

    We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analyzing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Barth and Smirnova (2013 Phys. Rev. A 88 013401). We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields. (paper)

  10. Stability estimate for the aligned magnetic field in a periodic quantum waveguide from Dirichlet-to-Neumann map

    Energy Technology Data Exchange (ETDEWEB)

    Mejri, Youssef, E-mail: josef-bizert@hotmail.fr [Aix Marseille Universite, Toulon Universite, CNRS, CPT, Marseille (France); Dép. des Mathématiques, Faculté des Sciences de Bizerte, 7021 Jarzouna (Tunisia); Laboratoire de Modélisation Mathématique et Numérique dans les Sciences de l’Ingénieur, ENIT BP 37, Le Belvedere, 1002 Tunis (Tunisia)

    2016-06-15

    In this article, we study the boundary inverse problem of determining the aligned magnetic field appearing in the magnetic Schrödinger equation in a periodic quantum cylindrical waveguide, by knowledge of the Dirichlet-to-Neumann map. We prove a Hölder stability estimate with respect to the Dirichlet-to-Neumann map, by means of the geometrical optics solutions of the magnetic Schrödinger equation.

  11. Externe verslaggeving How do current public Integrated Reports align with the IR Framework?

    NARCIS (Netherlands)

    Hurks, P.; Langendijk, H.P.A.J.; Nandram, K.

    2016-01-01

    This paper examines empirically the current practice with regard to integrated reporting according to the IR Framework among the 104 original participants (companies) of the IIRC Pilot program. We made a selection with respect to these 104 participants based on organization’s stipulation that they

  12. Revival structures of linear molecules in a field-free alignment condition as probed by high-order harmonic generation

    International Nuclear Information System (INIS)

    Lee, G. H.; Kim, H. T.; Park, J. Y.; Nam, C. H.; Kim, T. K.; Lee, J. H.; Ihee, H.

    2006-01-01

    Revival structures (rotational coherence) of three linear molecules (N 2 , O 2 , and CO 2 ) in a field free alignment condition have been investigated using high-order harmonic generation. The harmonic yields of these molecules were measured in a pump-probe manner by using a weak femtosecond (fs) laser pulse for field-free alignment of molecules and another intense fs laser pulse for harmonic generation. The harmonic intensities from 23rd to 29th order with respect to the time delay between the pump and the probe pulses showed revival structures in the condition of a field-free alignment of molecules. While the revival structure of a N 2 molecule had one-fourth the period of the full revival time and different degrees of modulation among different fractional revival times, the revival structures of O 2 and CO 2 molecules showed one-eighth the periods of the full revival time and similar degrees of modulation among all fractional revival times. The revival structures could be interpreted in terms of the nature of the highest occupied molecular orbital and the total nuclear spin.

  13. Motionally-induced electromagnetic fields generated by idealized ocean currents

    Science.gov (United States)

    Tyler, R. H.; Mysak, L. A.

    Using the induction equation, we investigate the generation of electromagnetic fields by the motional electromagnetic induction due to ocean currents. In this paper, solutions are presented for a linear induction equation for the magnetic flux density vector which contains prescribed time-independent ocean current and conductivity fields. Once the magnetic flux density is known, the electric field and electric current density are easily obtained by differentiation. Solutions are given for several examples of idealized flow which include: 1) Vertically and horizontally sheared plane-parallel flow with depth-dependent conductivity; 2) A simple Stommel circulation gyre; and 3) Symmetric gyres. The results indicate that typical ocean current features induce magnetic fields with magnitudes reaching 100's of nT within the water and about 1-10 outside of the water. For the case of a field of gyres, the ocean-induced magnetic fields decay away from the ocean on spatial scales set by the horizontal scale of the ocean feature. At the altitudes of magnetic field satellite surveys, ocean-induced magnetic fields may retain values of a few nT, which are strong enough to be detected. Thus it is concluded that satellite observations of the earth's main magnetic field and, in particular, the observed temporal variations, could be affected by the ocean circulation. Summary and discussion In Section 3, we found exact solutions to the induction equation for idealized flows. The results gave magnitudes of about tens to hundreds of nT for the magnetic fields bH, about 10-5 V/m for the electric fields E, and about 10-5 A/m2 for the electric current density J induced by the ocean currents. These figures are in general agreement with the calculations of Lilley et al. (1993). In Section 4.2 we obtained solutions for the magnetic field above the ocean surface for the case of a Stommel gyre and a field of symmetric gyres. It was found in the last case that ocean gyres with a total transport

  14. The electric field of a current-carrying conductor

    International Nuclear Information System (INIS)

    Strel'tsov, V.N.

    1991-01-01

    A subject concerning the relativistic invariance of the Gauss theorem has been discussed. The appearance of the electric field around the neutral conductor after excitation of current in it doesn't signify the change of its charge. 8 refs.; 1 fig

  15. Construction of theoretical F-spread ionogams from scattering in the HF band from field-aligned irregularities

    International Nuclear Information System (INIS)

    Powers, W.J.

    1985-01-01

    The scattering and propagation of electromagnetic fields in the ionosphere for the HF band is considered. Particular attention is given to scattering at the geomagnetic equator from irregularities of ionization density that are aligned along the earth's magnetic field and that have lengths that are much greater than a Fresnel scale. Perpendicular to the earth's magnetic field the irregularities are assumed to be isotropic with scale lengths (wavelengths /(2π)) extending from an inner scale equal to the ionic gyroradius to an outer scale on the order of the scale height of the ionosphere. Primary emphasis is placed on the weak scattering of pulses from field-aligned irregularities embedded in the night time F-layer, with application to explaining F-spread ionograms. The average ionization density of the night time F-layer is assumed to be well modeled by a parabolic layer. Assuming that the effects of the earth's magnetic field and collisions can be neglected, an approximate dyadic Green's function is derived and utilized in the determination of the incident and singly scattered fields

  16. Effects of atmospheric oscillations on the field-aligned ion motions in the polar F-region

    Directory of Open Access Journals (Sweden)

    S. Oyama

    Full Text Available The field-aligned neutral oscillations in the F-region (altitudes between 165 and 275 km were compared using data obtained simultaneously with two independent instruments: the European Incoherent Scatter (EISCAT UHF radar and a scanning Fabry-Perot interferometer (FPI. During the night of February 8, 1997, simultaneous observations with these instruments were conducted at Tromsø, Norway. Theoretically, the field-aligned neutral wind velocity can be obtained from the field-aligned ion velocity and by diffusion and ambipolar diffusion velocities. We thus derived field-aligned neutral wind velocities from the plasma velocities in EISCAT radar data. They were compared with those observed with the FPI (λ=630.0 nm, which are assumed to be weighted height averages of the actual neutral wind. The weighting function is the normalized height dependent emission rate. We used two model weighting functions to derive the neutral wind from EISCAT data. One was that the neutral wind velocity observed with the FPI is velocity integrated over the entire emission layer and multiplied by the theoretical normalized emission rate. The other was that the neutral wind velocity observed with the FPI corresponds to the velocity only around an altitude where the emission rate has a peak. Differences between the two methods were identified, but not completely clarified. However, the neutral wind velocities from both instruments had peak-to-peak correspondences at oscillation periods of about 10–40 min, shorter than that for the momentum transfer from ions to neutrals, but longer than from neutrals to ions. The synchronizing motions in the neutral wind velocities suggest that the momentum transfer from neutrals to ions was thought to be dominant for the observed field-aligned oscillations rather than the transfer from ions to neutrals. It is concluded that during the observation, the plasma oscillations observed with the EISCAT radar at different altitudes

  17. Nanosecond field emitted and photo-field emitted current pulses from ZrC tips

    International Nuclear Information System (INIS)

    Ganter, R.; Bakker, R.J.; Gough, C.; Paraliev, M.; Pedrozzi, M.; Le Pimpec, F.; Rivkin, L.; Wrulich, A.

    2006-01-01

    In order to find electron sources with low thermal emittance, cathodes based on single tip field emitter are investigated. Maximum peak current, measured from single tip in ZrC with a typical apex radius around 1 μm, are presented. Voltage pulses of 2 ns duration and up to 50 kV amplitude lead to field emission current up to 470 mA from one ZrC tip. Combination of high applied electric field with laser illumination gives the possibility to modulate the emission with laser pulses. Nanoseconds current pulses have been emitted with laser pulses at 1064 nm illuminating a ZrC tip under high-DC electric field. The dependence of photo-field emitted current with the applied voltage can be explained by the Schottky effect

  18. Nanosecond field emitted and photo-field emitted current pulses from ZrC tips

    Energy Technology Data Exchange (ETDEWEB)

    Ganter, R. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland)]. E-mail: romain.ganter@psi.ch; Bakker, R.J. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Gough, C. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Paraliev, M. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Pedrozzi, M. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Le Pimpec, F. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Rivkin, L. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland); Wrulich, A. [Paul Scherrer Institut, Villigen, CH 5232 (Switzerland)

    2006-09-15

    In order to find electron sources with low thermal emittance, cathodes based on single tip field emitter are investigated. Maximum peak current, measured from single tip in ZrC with a typical apex radius around 1 {mu}m, are presented. Voltage pulses of 2 ns duration and up to 50 kV amplitude lead to field emission current up to 470 mA from one ZrC tip. Combination of high applied electric field with laser illumination gives the possibility to modulate the emission with laser pulses. Nanoseconds current pulses have been emitted with laser pulses at 1064 nm illuminating a ZrC tip under high-DC electric field. The dependence of photo-field emitted current with the applied voltage can be explained by the Schottky effect.

  19. Eddy current calculations for the Tore Supra toroidal field magnet

    International Nuclear Information System (INIS)

    Blum, J.

    1983-01-01

    An outline is given of the calculation of the eddy currents in the magnetic structures of a Tokamak, which can be assimilated to thin conductors, so that the three-dimensional problem can be reduced mathematically to a two-dimensional one, the variables being two orthogonal coordinates of the considered surface. A finite element method has been used in order to treat the complicated geometry of the set of the 18 toroidal field coil casings and mechanical structures of Tore Supra. This eddy current code has been coupled with an axisymmetric equilibrium code in order to simulate typical phases of a Tokamak discharge (plasma current rise, additional heating, disruption, cleaning discharge) and the losses in the toroidal field magnet have thus been calculated. (author)

  20. Elliptically polarized high-order harmonics from aligned molecules within the strong-field approximation

    DEFF Research Database (Denmark)

    Etches, Adam; Madsen, Christian Bruun; Madsen, Lars Bojer

    A correction term is introduced in the stationary-point analysis on high-order harmonic generation (HHG) from aligned molecules. Arising from a multi-centre expansion of the electron wave function, this term brings our numerical calculations of the Lewenstein model into qualitative agreement...

  1. Far-field and Fresnel Liquid Crystal Geometric Phase Holograms via Direct-Write Photo-Alignment

    Directory of Open Access Journals (Sweden)

    Xiao Xiang

    2017-12-01

    Full Text Available We study computer-generated geometric-phase holograms (GPHs realized by photo-aligned liquid crystals, in both simulation and experiment. We demonstrate both far-field and Fresnel holograms capable of producing far-field and near-field images with preserved fidelity for all wavelengths. The GPHs are fabricated by patterning a photo-alignment layer (PAL using a direct-write laser scanner and coating the surface with a polymerizable liquid crystal (i.e., a reactive mesogen. We study various recording pixel sizes, down to 3 μm, that are easily recorded in the PAL. We characterize the fabricated elements and find good agreement with theory and numerical simulation. Because of the wavelength independent geometric phase, the (phase fidelity of the replay images is preserved for all wavelengths, unlike conventional dynamic phase holograms. However, governed by the diffraction equation, the size and location of a reconstructed image depends on the replay wavelength for far-field and near-field GPHs, respectively. These offer interesting opportunities for white-light holography.

  2. Electric field control photo-induced Hall currents in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Miah, M. Idrish [Nanoscale Science and Technology Centre, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong 4331 (Bangladesh)], E-mail: m.miah@griffith.edu.au

    2008-10-15

    We generate spin-polarized carrier populations in GaAs and low temperature-grown GaAs (LT-GaAs) by circularly polarized optical beams and pull them by external electric fields to create spin-polarized currents. In the presence of the optically generated spin currents, anomalous Hall currents with an enhancement with increasing doping are observed and found to be almost steady in moderate electric fields up to {approx}120 mV {mu}m{sup -1}, indicating that photo-induced spin orientation of electrons is preserved in these systems. However, a field {approx}300 mV {mu}m{sup -1} completely destroys the electron spin polarization due to an increase of the D'yakonov-Perel' spin precession frequency of the hot electrons. This suggests that high field carrier transport conditions might not be suitable for spin-based technology with GaAs and LT-GaAs. It is also demonstrated that the presence of the excess arsenic sites in LT-GaAs might not affect the spin relaxation by Bir-Aronov-Pikus mechanism owing to a large number of electrons in n-doped materials.

  3. Measurement of Coherent Emission and Linear Polarization of Photons by Electrons in the Strong Fields of Aligned Crystals

    CERN Document Server

    Apyan, A.; Badelek, B.; Ballestrero, S.; Biino, C.; Birol, I.; Cenci, P.; Connell, S.H.; Eichblatt, S.; Fonseca, T.; Freund, A.; Gorini, B.; Groess, R.; Ispirian, K.; Ketel, T.J.; Kononets, Yu.V.; Lopez, A.; Mangiarotti, A.; van Rens, B.; Sellschop, J.P.F.; Shieh, M.; Sona, P.; Strakhovenko, V.; Uggerhoj, E.; Uggerhj, Ulrik Ingerslev; Unel, G.; Velasco, M.; Vilakazi, Z.Z.; Wessely, O.; Kononets, Yu.V.

    2004-01-01

    We present new results regarding the features of high energy photon emission by an electron beam of 178 GeV penetrating a 1.5 cm thick single Si crystal aligned at the Strings-Of-Strings (SOS) orientation. This concerns a special case of coherent bremsstrahlung where the electron interacts with the strong fields of successive atomic strings in a plane and for which the largest enhancement of the highest energy photons is expected. The polarization of the resulting photon beam was measured by the asymmetry of electron-positron pair production in an aligned diamond crystal analyzer. By the selection of a single pair the energy and the polarization of individual photons could be measured in an the environment of multiple photons produced in the radiator crystal. Photons in the high energy region show less than 20% linear polarization at the 90% confidence level.

  4. Method of making a self-aligned schottky metal semi-conductor field effect transistor with buried source and drain

    International Nuclear Information System (INIS)

    Bol, I.

    1984-01-01

    A semi-conductor structure and particularly a high speed VLSI Self-Aligned Schottky Metal Semi-Conductor Field Effect Transistor with buried source and drain, fabricated by the ion implantation of source and drain areas at a predetermined range of depths followed by very localized laser annealing to electrically reactivate the amorphous buried source and drain areas thereby providing effective vertical separation of the channel from the buried source and drain respectively. Accordingly, spatial separations between the self-aligned gate-to-drain, and gate-to-source can be relatively very closely controlled by varying the doping intensity and duration of the implantation thereby reducing the series resistance and increasing the operating speed

  5. A model for electron currents near a field null

    International Nuclear Information System (INIS)

    Stark, R.A.; Miley, G.H.

    1987-01-01

    The fluid approximation is invalid near a field null, since the local electron orbit size and the magnetic scale length are comparable. To model the electron currents in this region we propose a single equation of motion describing the bulk electron dynamics. The equation applies to the plasma within one thermal orbit size of the null. The region is treated as unmagnetized; electrons are accelerated by the inductive electric field and drag on ions; damping is provided by viscosity due to electrons and collisions with ions. Through variational calculations and a particle tracking code for electrons, the size of the terms in the equation of motion have been estimated. The resulting equation of motion combines with Faraday's Law to produce a governing equation which implicitly contains the self inductive field of the electrons. This governing equation predicts that viscosity prevents complete cancellation of the ion current density by the electrons in the null region. Thus electron dynamics near the field null should not prevent the formation and deepening of field reversal using neutral-beam injection

  6. Critical currents and fields of disordered nanocrystalline superconductors

    International Nuclear Information System (INIS)

    Yavary, H.; Shahzamanian, M.A.; Rabbani, H.

    2007-01-01

    Full text: There is an enormous effort directed at increasing the upper critical field of the superconducting materials because this upper critical field provides a fundamental limit to the maximum field a magnet system can produce. High-energy particle accelerators and medical resonance imaging body scanners are limited by the for NbTi (10 T). Gigahertz class nuclear-magnetic-resonance and high field laboratory magnets are limited by for Nb 3 Sn (23 T) [1]. However, the values of critical current density are too low for industrial use, possibly because of degraded or nonsuperconducting phases, such as MoS 2 or Mo 2 S 3 , at the grain boundaries or because the pinning site density is not high enough. It has long been known that decreasing the grain size of low-temperature superconducting (LTS) materials, such as Nb 3 Sn, increases the density of flux pinning sites and hence. Nanocrystalline materials are characterized by ultrafine grains and a high density of grain boundaries [2]. Hence nanocrystalline materials can exhibit unusual physical, chemical, and mechanical properties with respect to conventional polycrystalline materials. The purpose of this paper is to investigate the structure of currents and fields in disordered nanocrystalline superconducting materials by the use of quasiclassical many body techniques. The Keldish Greens functions are used to calculate the current density of the system. Since the disorder and microstructure of these nanocrystalline materials are on a sufficiently short length scale as to increase both the density of pinning site and the upper critical field. (authors)

  7. Energy confinement in a high-current reversed field pinch

    International Nuclear Information System (INIS)

    An, Z.G.; Lee, G.S.; Diamond, P.H.

    1985-07-01

    The ion temperature gradient driven (eta/sub i/) mode is proposed as a candidate for the cause of anomalous transport in high current reversed field pinches. A 'four-field' fluid model is derived to describe the coupled nonlinear evolution of resistive interchange and eta/sub i/ modes. A renormalized theory is discussed, and the saturation level of the fluctuations is analytically estimated. Transport scalings are obtained, and their implications discussed. In particular, these results indicate that pellet injection is a potentially viable mechanism for improving energy confinement in a high temperature RFP

  8. Action potential propagation: ion current or intramembrane electric field?

    Science.gov (United States)

    Martí, Albert; Pérez, Juan J; Madrenas, Jordi

    2018-01-01

    The established action potential propagation mechanisms do not satisfactorily explain propagation on myelinated axons given the current knowledge of biological channels and membranes. The flow across ion channels presents two possible effects: the electric potential variations across the lipid bilayers (action potential) and the propagation of an electric field through the membrane inner part. The proposed mechanism is based on intra-membrane electric field propagation, this propagation can explain the action potential saltatory propagation and its constant delay independent of distance between Ranvier nodes in myelinated axons.

  9. Direct-current-like Phase Space Manipulation Using Chirped Alternating Current Fields

    International Nuclear Information System (INIS)

    Schmit, P.F.; Fisch, N.J.

    2010-01-01

    Waves in plasmas can accelerate particles that are resonant with the wave. A dc electric field also accelerates particles, but without a resonance discrimination, which makes the acceleration mechanism profoundly different. Whereas wave-particle acceleration mechanisms have been widely discussed in the literature, this work discusses the direct analogy between wave acceleration and dc field acceleration in a particular parameter regime explored in previous works. Apart from the academic interest of this correspondence, there may be practical advantages in using waves to mimic dc electric fields, for example, in driving plasma current with high efficiency.

  10. Field modulation of the critical current in magnetic Josephson junctions

    International Nuclear Information System (INIS)

    Blamire, M G; Smiet, C B; Banerjee, N; Robinson, J W A

    2013-01-01

    The dependence of the critical current of a simple Josephson junction on the applied magnetic field is well known and, for a rectangular junction, gives rise to the classic ‘Fraunhofer’ modulation with periodic zeros at the fields that introduce a flux quantum into the junction region. Much recent work has been performed on Josephson junctions that contain magnetic layers. The magnetization of such layers introduces additional flux into the junction and, for large junction areas or strong magnetic materials, can significantly distort the modulation of the critical current and strongly suppress the maximum critical current. The growing interest in junctions that induce odd-frequency triplet pairing in a ferromagnet, and the need to make quantitative comparisons with theory, mean that a full understanding of the role of magnetic barriers in controlling the critical current is necessary. This paper analyses the effect of magnetism and various magnetic configurations on Josephson critical currents; the overall treatment applies to junctions of general shape, but the specific cases of square and rectangular junctions are considered. (paper)

  11. Superconducting toroidal field coil current densities for the TFCX

    International Nuclear Information System (INIS)

    Kalsi, S.S.; Hooper, R.J.

    1985-04-01

    A major goal of the Tokamak Fusion Core Experiment (TFCX) study was to minimize the size of the device and achieve lowest cost. Two key factors influencing the size of the device employing superconducting magnets are toroidal field (TF) winding current density and its nuclear heat load withstand capability. Lower winding current density requires larger radial build of the winding pack. Likewise, lower allowable nuclear heating in the winding requires larger shield thickness between the plasma and coil. In order to achieve a low-cost device, it is essential to maximize the winding's current density and nuclear heating withhstand capability. To meet the above objective, the TFCX design specification adopted as goals a nominal winding current density of 3500 A/cm 2 with 10-T peak field at the winding and peak nuclear heat load limits of 1 MW/cm 3 for the nominal design and 50 MW/cm 3 for an advanced design. This study developed justification for these current density and nuclear heat load limits

  12. Exploration of a possible cause of magnetic reconfiguration/reconnection due to generation, rather than annihilation, of magnetic field in a nun-uniform thin current sheet

    Science.gov (United States)

    Huang, Y. C.; Lyu, L. H.

    2014-12-01

    Magnetic reconfiguration/reconnection plays an important role on energy and plasma transport in the space plasma. It is known that magnetic field lines on two sides of a tangential discontinuity can connect to each other only at a neutral point, where the strength of the magnetic field is equal to zero. Thus, the standard reconnection picture with magnetic field lines intersecting at the neutral point is not applicable to the component reconnection events observed at the magnetopause and in the solar corona. In our early study (Yu, Lyu, & Wu, 2011), we have shown that annihilation of magnetic field near a thin current sheet can lead to the formation of normal magnetic field component (normal to the current sheet) to break the frozen-in condition and to accelerate the reconnected plasma flux, even without the presence of a neutral point. In this study, we examine whether or not a generation, rather than annihilation, of magnetic field in a nun-uniform thin current sheet can also lead to reconnection of plasma flux. Our results indicate that a non-uniform enhancement of electric current can yield formation of field-aligned currents. The normal-component magnetic field generated by the field-aligned currents can yield reconnection of plasma flux just outside the current-enhancement region. The particle motion that can lead to non-uniform enhancement of electric currents will be discussed.

  13. Magnetic field behavior of current steps in long Josephson junctions

    International Nuclear Information System (INIS)

    Costabile, G.; Cucolo, A.M.; Pace, S.; Parmentier, R.D.; Savo, B.; Vaglio, R.

    1980-01-01

    The zero-field steps, or dc current singularities, in the current-voltage characteristics of long Josephson tunnel junctions, first reported by Chen et al., continue to attract research interest both because their study can provide fundamental information on the dynamics of fluxons in such junctions and because they are accompanied by the emission of microwave radiation from the junction, which may be exploitable in practical oscillator applications. The purpose of this paper is to report some experimental observations of the magnetic field behavior of the steps in junctions fabricated in our Laboratory and to offer a qualitative explanation for this behavior. Measurements have been made both for very long (L >> lambdasub(J)) and for slightly long (L approx. >= lambdasub(J)) junctions with a view toward comparing our results with those of other workers. (orig./WRI)

  14. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Venkattraman, Ayyaswamy [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2013-11-15

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission.

  15. Cathode fall model and current-voltage characteristics of field emission driven direct current microplasmas

    International Nuclear Information System (INIS)

    Venkattraman, Ayyaswamy

    2013-01-01

    The post-breakdown characteristics of field emission driven microplasma are studied theoretically and numerically. A cathode fall model assuming a linearly varying electric field is used to obtain equations governing the operation of steady state field emission driven microplasmas. The results obtained from the model by solving these equations are compared with particle-in-cell with Monte Carlo collisions simulation results for parameters including the plasma potential, cathode fall thickness, ion number density in the cathode fall, and current density vs voltage curves. The model shows good overall agreement with the simulations but results in slightly overpredicted values for the plasma potential and the cathode fall thickness attributed to the assumed electric field profile. The current density vs voltage curves obtained show an arc region characterized by negative slope as well as an abnormal glow discharge characterized by a positive slope in gaps as small as 10 μm operating at atmospheric pressure. The model also retrieves the traditional macroscale current vs voltage theory in the absence of field emission

  16. Magnetic fields with photon beams: Use of circular current loops

    International Nuclear Information System (INIS)

    Jette, David

    2001-01-01

    Strong transverse magnetic fields can produce very large dose enhancements and reductions in localized regions of a patient under irradiation by a photon beam. Through EGS4 Monte Carlo simulations, we have examined the effects of applying a magnetic field produced by a pair of circular current loops to a photon beam penetrating a water phantom of finite thickness. We have indeed found very substantial localized dose enhancements, albeit with no corresponding dose reduction just distal to the region of dose enhancement. (However, dose reduction does occur near the distal end of the phantom.) We have also observed two phenomena to be concerned with, for this configuration: significant broadening of the penumbra close to the current loop, and narrowness of the enhanced dose region in a plane parallel to the planes of the loops. We have also examined the use of a single current loop to produce the magnetic field, and have found great asymmetry in the dose distribution; this asymmetry appears to make it impossible to treat with a single circular magnet a tumor of large dimension extending below the application surface

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  18. Modular constraints on conformal field theories with currents

    Science.gov (United States)

    Bae, Jin-Beom; Lee, Sungjay; Song, Jaewon

    2017-12-01

    We study constraints coming from the modular invariance of the partition function of two-dimensional conformal field theories. We constrain the spectrum of CFTs in the presence of holomorphic and anti-holomorphic currents using the semi-definite programming. In particular, we find the bounds on the twist gap for the non-current primaries depend dramatically on the presence of holomorphic currents, showing numerous kinks and peaks. Various rational CFTs are realized at the numerical boundary of the twist gap, saturating the upper limits on the degeneracies. Such theories include Wess-Zumino-Witten models for the Deligne's exceptional series, the Monster CFT and the Baby Monster CFT. We also study modular constraints imposed by W -algebras of various type and observe that the bounds on the gap depend on the choice of W -algebra in the small central charge region.

  19. Mobile media, mobility and mobilisation in the current museum field

    DEFF Research Database (Denmark)

    Baggesen, Rikke Haller

    2017-01-01

    Introducing the concept of a 'mobile museology' to describe how museums are currently set in motion by a confluence of cultural, technological and museological developments, this chapter traces the connections between mobile media and notions of mobility and mobilisation in the museum field....... As illustrated by current examples in the chapter, mobile phones have thus provided an opportunity for both augmenting and transcending the museum space, blurring former boundaries between institutions and their environments. At the same time, technological advances and digitial culture developments have also...... required and inspired museums to become organisationally mobile, and to mobilise collections, audiences and institutions in order to fulfill museum missions. In this perspective, mobile media are thus seen as both catalysts and instruments for current museum developments....

  20. Magnetohydrodynamic effects of current profile control in reversed field pinches

    International Nuclear Information System (INIS)

    Sovinec, C.R.; Prager, S.C.

    1999-01-01

    Linear and non-linear MHD computations are used to investigate reversed field pinch configurations with magnetic fluctuations reduced through current profile control. Simulations with reduced ohmic drive and moderate auxiliary current drive, represented generically with an electron force term, applied locally in radius near the plasma edge show magnetic fluctuation energies that are orders of magnitude smaller than those in simulations without profile control. The core of the improved configurations has reduced magnetic shear and closed flux surfaces in some cases, and reversal is sustained through the auxiliary current drive. Modes resonant near the edge may become unstable with auxiliary drive, but their saturation levels can be controlled. The space of auxiliary drive parameters is explored, and the ill effects of deviating far from optimal conditions is demonstrated in non-linear simulations. (author)

  1. Effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field

    International Nuclear Information System (INIS)

    Chen Jianxin; Cui Xiaomei; Huang Bomin; Wu Hongchun; Zhuo Shuangmu

    2006-01-01

    In the rotation equation of the angle θ between the molecular axis and the laser polarization direction, the dependence of laser-induced polarizability on the molecular internuclear distance R is considered. The effect of the R dependence of laser-induced polarizability on molecular dynamic alignment in an intense femtosecond laser field is investigated with 20 and 100 fs laser pulses for N 2 molecules and with 60 and 100 fs laser pulses for Br 2 molecules at intensities of 5x10 14 W cm -2 and 5x10 15 W cm -2 . This effect exists and only occurs during the dissociative process after the molecule is ionized. It enhances the degrees of molecular dynamic alignment and is more significant in reorienting the angular distributions of molecules towards the laser polarization direction in the conditions of high laser intensity and short pulse length. Compared with the N 2 molecule, the effect of the R dependence of laser-induced polarizability on molecular dynamic alignment for Br 2 is stronger. The reasons are presented and discussed

  2. Alternative current source based Schottky contact with additional electric field

    Science.gov (United States)

    Mamedov, R. K.; Aslanova, A. R.

    2017-07-01

    Additional electric field (AEF) in the Schottky contacts (SC) that covered the peripheral contact region wide and the complete contact region narrow (as TMBS diode) SC. Under the influence of AEF is a redistribution of free electrons produced at certain temperatures of the semiconductor, and is formed the space charge region (SCR). As a result of the superposition of the electric fields SCR and AEF occurs the resulting electric field (REF). The REF is distributed along a straight line perpendicular to the contact surface, so that its intensity (and potential) has a minimum value on the metal surface and the maximum value at a great distance from the metal surface deep into the SCR. Under the influence of AEF as a sided force the metal becomes negative pole and semiconductor - positive pole, therefore, SC with AEF becomes an alternative current source (ACS). The Ni-nSi SC with different diameters (20-1000 μm) under the influence of the AEF as sided force have become ACS with electromotive force in the order of 0.1-1.0 mV, which are generated the electric current in the range of 10-9-10-7 A, flowing through the external resistance 1000 Ohm.

  3. Field-emission from parabolic tips: Current distributions, the net current, and effective emission area

    Science.gov (United States)

    Biswas, Debabrata

    2018-04-01

    Field emission from nano-structured emitters primarily takes place from the tips. Using recent results on the variation of the enhancement factor around the apex [Biswas et al., Ultramicroscopy 185, 1-4 (2018)], analytical expressions for the surface distribution of net emitted electrons, as well as the total and normal energy distributions are derived in terms of the apex radius Ra and the local electric field at the apex Ea. Formulae for the net emitted current and effective emission area in terms of these quantities are also obtained.

  4. Joint two-dimensional observations of ground magnetic and ionospheric electric fields associated with auroral zone currents 1. Three-dimensional current flows associated with a substorm-intensified eastward electrojet

    International Nuclear Information System (INIS)

    Baumjohann, W.; Untiedt, J.; Greenwald, R.A.

    1980-01-01

    Two-dimensional distributions of ground magnetic and ionospheric electric fields in the evening sector auroral oval have been simultaneously observed by the Scandinavian Magnetometer Array and the Scandinavian Twin Auroral Radar Experiment (Stare) radars, respectively, on February 15, 1977. They were associated with varying, substorm-intensified, eastward electrojet current systems of the western, middle, and eastern segment of the eastward electrojet. We conclude that the substorm-intensified eastward electroject was a nearly pure Hall current driven by northward electric fields. The observed eastward increase of the current in the western segment of the electrojet was due to a gradual enhancement of the Hall conductivity. Here, the electrojet was fed by a broad sheet of net downward field-aligned current. During one period, the eastern-terminating part of the eastward electrojet diverged up the field lines in a rather local area because of a strong longitudinal decrease in the northward-directed electric field. On another occasion, it diverged northward within the ionosphere and joined the westward-flowing current because of a rotation of the northward electric field with increasing latitude through west- to southward. These two observed mechanisms of current divergence in the region where eastward and westward electrojects coexist may shed some new light on the controversy over the existence of upward field-aligned current flow in the Harang discontinuity

  5. Computer simulation of induced electric currents and fields in biological bodies by 60 Hz magnetic fields

    International Nuclear Information System (INIS)

    Xi Weiguo; Stuchly, M.A.; Gandhi, O.P.

    1993-01-01

    Possible health effects of human exposure to 60 Hz magnetic fields are a subject of increasing concern. An understanding of the coupling of electromagnetic fields to human body tissues is essential for assessment of their biological effects. A method is presented for the computerized simulation of induced electric currents and fields in bodies of men and rodents from power-line frequency magnetic fields. In the impedance method, the body is represented by a 3 dimensional impedance network. The computational model consists of several tens of thousands of cubic numerical cells and thus represented a realistic shape. The modelling for humans is performed with two models, a heterogeneous model based on cross-section anatomy and a homogeneous one using an average tissue conductivity. A summary of computed results of induced electric currents and fields is presented. It is confirmed that induced currents are lower than endangerous current levels for most environmental exposures. However, the induced current density varies greatly, with the maximum being at least 10 times larger than the average. This difference is likely to be greater when more detailed anatomy and morphology are considered. 15 refs., 2 figs., 1 tab

  6. High current superconductors for tokamak toroidal field coils

    International Nuclear Information System (INIS)

    Fietz, W.A.

    1976-01-01

    Conductors rated at 10,000 A for 8 T and 4.2 K are being purchased for the first large coil segment tests at ORNL. Requirements for these conductors, in addition to the high current rating, are low pulse losses, cryostatic stability, and acceptable mechanical properties. The conductors are required to have losses less than 0.4 W/m under pulsed fields of 0.5 T with a rise time of 1 sec in an ambient 8-T field. Methods of calculating these losses and techniques for verifying the performance by direct measurement are discussed. Conductors stabilized by two different cooling methods, pool boiling and forced helium flow, have been proposed. Analysis of these conductors is presented and a proposed definition and test of stability is discussed. Mechanical property requirements, tensile and compressive, are defined and test methods are discussed

  7. Lower hybrid current drive in the presence of electric field

    Directory of Open Access Journals (Sweden)

    Saveliev Alexander

    2017-01-01

    Full Text Available A new one-dimensional approach to the lower hybrid current drive (LHCD modelling in the presence of an inductive electric field is suggested in this paper. The approach is based on using time-dependent solutions of a well-known Fokker-Planck equation for the distribution function of fast electrons calculated concurrently with solving plasma transport equation in the Automated System for TRansport Analysis (ASTRA [1]. A good agreement between experimental and modelling results is demonstrated for an FT-2 [2] plasma shot. Also new formulae for the steady-state solution of this kinetic equation are found.

  8. Lower hybrid current drive in the presence of electric field

    Science.gov (United States)

    Saveliev, Alexander; Zakharov, Vladimir

    2017-10-01

    A new one-dimensional approach to the lower hybrid current drive (LHCD) modelling in the presence of an inductive electric field is suggested in this paper. The approach is based on using time-dependent solutions of a well-known Fokker-Planck equation for the distribution function of fast electrons calculated concurrently with solving plasma transport equation in the Automated System for TRansport Analysis (ASTRA) [1]. A good agreement between experimental and modelling results is demonstrated for an FT-2 [2] plasma shot. Also new formulae for the steady-state solution of this kinetic equation are found.

  9. Field-parallel Acceleration: Comment on the Paper “Electric Currents on the Flare Ribbons: Observations and Standard Model” by Janvier et al. (2014, ApJ, 788, 60)

    Energy Technology Data Exchange (ETDEWEB)

    Haerendel, G. [Max Planck Institute for Extraterrestrial Physics, Garching (Germany)

    2017-10-01

    It is proposed that the coincidence of higher brightness and upward electric current observed by Janvier et al. during a flare indicates electron acceleration by field-parallel potential drops sustained by extremely strong field-aligned currents of order 10{sup 4} A m{sup −2}. A few consequences are discussed here.

  10. Relation between magnetic fields and electric currents in plasmas

    Directory of Open Access Journals (Sweden)

    V. M. Vasyliunas

    2005-10-01

    Full Text Available Maxwell's equations allow the magnetic field B to be calculated if the electric current density J is assumed to be completely known as a function of space and time. The charged particles that constitute the current, however, are subject to Newton's laws as well, and J can be changed by forces acting on charged particles. Particularly in plasmas, where the concentration of charged particles is high, the effect of the electromagnetic field calculated from a given J on J itself cannot be ignored. Whereas in ordinary laboratory physics one is accustomed to take J as primary and B as derived from J, it is often asserted that in plasmas B should be viewed as primary and J as derived from B simply as (c/4π∇×B. Here I investigate the relation between ∇×B and J in the same terms and by the same method as previously applied to the MHD relation between the electric field and the plasma bulk flow vmv2001: assume that one but not the other is present initially, and calculate what happens. The result is that, for configurations with spatial scales much larger than the electron inertial length λe, a given ∇×B produces the corresponding J, while a given J does not produce any ∇×B but disappears instead. The reason for this can be understood by noting that ∇×B≠4π/cJ implies a time-varying electric field (displacement current which acts to change both terms (in order to bring them toward equality; the changes in the two terms, however, proceed on different time scales, light travel time for B and electron plasma period for J, and clearly the term changing much more slowly is the one that survives. (By definition, the two time scales are equal at λe. On larger scales, the evolution of B (and hence also of ∇×B is governed by

  11. Electrostatic lower hybrid waves excited by electromagnetic whistler mode waves scattering from planar magnetic-field-aligned plasma density irregularities

    International Nuclear Information System (INIS)

    Bell, T.F.; Ngo, H.D.

    1990-01-01

    Recent satellite observations demonstrate that high amplitude, short wavelength (5 m ≤ λ ≤ 100 m) electrostatic waves are commonly excited by electromagnetic whistler mode waves propagating in regions of the magnetosphere and topside ionosphere where small-scale magnetic-field-aligned plasma density irregularities are thought to exist. A new theoretical model of this phenomenon is presented, based upon passive linear scattering in a cold magnetoplasma. In this model the electrostatic waves are excited by linear mode coupling as the incident electromagnetic whistler mode waves scatter from the magnetic-field-aligned plasma density irregularities. The excited short wavelength waves are quasi-electrostatic whistler mode waves, a type of lower hybrid wave, whose wave normal lies near the whistler mode resonance cone where the wave refractive index becomes very large. The amplitude of the excited electrostatic lower hybrid waves is calculated for a wide range of values of input electromagnetic wave frequency, wave normal direction, electron plasma frequency, gyrofrequency, ion composition, and irregularity scale and density enhancement. Results indicate that high amplitude lower hybrid waves can be excited over a wide range of parameters for irregularity density enhancements as low as 5% whenever the scale of the irregularity is of the same order as the lower hybrid wavelength

  12. Police Training to Align Law Enforcement and HIV Prevention: Preliminary Evidence From the Field

    Science.gov (United States)

    Agrawal, Alpna; Moreau, Bruce; Kumar, Pratima; Weiss-Laxer, Nomi; Heimer, Robert

    2011-01-01

    Having identified gaps in implementation of Rhode Island's syringe access law and police occupational safety education, public health and police professionals developed police training to boost legal knowledge, improve syringe access attitudes, and address needlestick injuries. Baseline data (94 officers) confirmed anxiety about needlestick injuries, poor legal knowledge, and occupational risk overestimation. Before training, respondents believed that syringe access promotes drug use (51%), increases likelihood of police needlestick injuries (58%), and fails to reduce epidemics (38%). Pretraining to posttraining evaluation suggested significant shifts in legal and occupational safety knowledge; changes in attitudes toward syringe access were promising. Training that combines occupational safety with syringe access content can help align law enforcement with public health goals. Additional research is needed to assess street-level effect and to inform intervention tailoring. PMID:21940924

  13. Remote sensing of local structure of the quasi-perpendicular Earth's bow shock by using field-aligned beams

    Directory of Open Access Journals (Sweden)

    B. Miao

    2009-03-01

    Full Text Available Field-aligned ion beams (FABs originate at the quasi-perpendicular Earth's bow shock and constitute an important ion population in the foreshock region. The bulk velocity of these FABs depends significantly on the shock normal angle, which is the angle between shock normal and upstream interplanetary magnetic field (IMF. This dependency may therefore be taken as an indicator of the local structure of the shock. Applying the direct reflection model to Cluster measurements, we have developed a method that uses proton FABs in the foreshock region for remote sensing of the local shock structure. The comparison of the model results with the multi-spacecraft observations of FAB events shows very good agreement in terms of wave amplitude and frequency of surface waves at the shock front.

  14. Current Understanding of the Health Effects of Electromagnetic Fields.

    Science.gov (United States)

    Miah, Tayaba; Kamat, Deepak

    2017-04-01

    There has been an exponential increase in the use of electronic devices over the past few decades. This has led to increased exposure to electromagnetic fields (EMF). Electric fields result from differences in voltage, whereas magnetic fields result from the flow of electric current. Higher-frequency waves of EMF have more energy than lower-frequency waves, and thus generally tend to be more harmful. An EMF activates cellular stress response and also causes breaks in DNA strands. There are many methodological barriers to effectively measuring the associations of EMF and childhood cancers. The consensus from multiple studies is that there is no causal role of extremely low-frequency EMFs in childhood cancers, including brain cancer. A recent study showed a link between EMF radiation and the development of malignant tumors in rats. In light of that study, the American Academy of Pediatrics set out new recommendations to decrease the adverse effects of cellphone exposure on children. [Pediatr Ann. 2017;46(4):e172-e174.]. Copyright 2017, SLACK Incorporated.

  15. Field mapping measurements to determine spatial and field dependence of critical current density in YBCO tapes

    International Nuclear Information System (INIS)

    Leclerc, J.; Berger, K.; Douine, B.; Lévêque, J.

    2013-01-01

    Highlights: • A method for characterizing superconducting tapes from field mapping is presented. • A new and efficient field mapping apparatus has been setup. • This method allows the spatial characterization of superconducting tapes. • The critical current density is obtained as a function of the flux density. • This method has been experimentally tested on an YBCO tape. -- Abstract: In this paper a measurement method that allows the determination of the critical current density of superconducting tape from field mapping measurements is presented. This contact-free method allows obtaining characteristics of the superconductor as a function of the position and of the applied flux density. With some modifications, this technique can be used for reel-to-reel measurements. The determination of the critical current density is based on an inverse calculation. This involves calculating the current distribution in the tape from magnetic measurements. An YBaCuO tape has been characterized at 77 K. A defect in this superconductor has been identified. Various tests were carried out to check the efficiency of the method. The inverse calculation was tested theoretically and experimentally. Comparison with a transport current measurement was also performed

  16. Enhancement of the guide field during the current sheet formation in the three-dimensional magnetic configuration with an X line

    International Nuclear Information System (INIS)

    Frank, Anna; Bugrov, Sergey; Markov, Vladimir

    2009-01-01

    Results are presented from studies of the formation of current sheets during exciting a current aligned with the X line of the 3D magnetic configuration, in the CS-3D device. Enhancement of the guide field (parallel to the X line) was directly observed for the first time, on the basis of magnetic measurements. After the current sheet formation, the guide field inside the sheet exceeds its initial value, as well as the field outside. It is convincingly demonstrated that an enhancement of the guide field is due to its transportation by plasma flows on the early stage of the sheet formation. The in-plane plasma currents, which produce the excess guide field, are comparable to the total current along the X line that initiates the sheet itself.

  17. DST Indices - Reflection Variations in the Magnetospheric Tail Current and Field-aligned Currents in the Magnetosphere

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The file is comprised of monthly DST indices. These indices are derived from a network of eight stations in the equatorial latitudes. Hourly DST indices provide an...

  18. Nonlinear analysis of generalized cross-field current instability

    International Nuclear Information System (INIS)

    Yoon, P.H.; Lui, A.T.Y.

    1993-01-01

    Analysis of the generalized cross-field current instability is carried out in which cross-field drift of both the ions and electrons and their temperatures are permitted to vary in time. The unstable mode under consideration is the electromagnetic generalization of the classical modified-two-stream instability. The generalized instability is made of the modified-two-stream and ion-Weibel modes. The relative importance of the features associated with the ion-Weibel mode and those of the modified-two-stream mode is assessed. Specific applications are made to the Earth's neutral sheet prior to substorm onset and to the Earth's bow shock. The numerical solution indicates that the ion-Weibel mode dominates in the Earth's neutral sheet environment. In contrast, the situation for the bow shock is dominated by the modified-two-stream mode. Notable differences are found between the present calculation and previous results on ion-Weibel mode which restrict the analysis to only parallel propagating waves. However, in the case of Earth's bow shock for which the ion-Weibel mode plays no important role, the inclusion of the electromagnetic ion response is found to differ little from the previous results which treats ions responding only to the electrostatic component of the excited waves

  19. The influence of magnetic field on the cold neutral medium mass fraction and its alignment with density structures

    Science.gov (United States)

    Villagran, M. A.; Gazol, A.

    2018-06-01

    To contribute to the understanding of the magnetic field's influence on the segregation of cold neutral medium (CNM) in the solar neighbourhood we analyse magnetohydrodynamic simulations that include the main physical characteristics of the local neutral atomic interstellar medium. The simulations have a continuous solenoidal Fourier forcing in a periodic box of 100 pc per side and an initial uniform magnetic field (B_0) with intensities ranging between ˜0.4 and ˜8 μG. Our main results are as follows. (i) The CNM mass fraction diminishes with the increase in magnetic field intensity. (ii) There is a preferred alignment between CNM structures and B in all our B0 range but the preference weakens as B0 increases. It is worth noticing that this preference is also present in two-dimensional projections making an extreme angle (0 or π / 2) with respect to B_0 and it is only lost for the strongest magnetic field when the angle of projection is perpendicular to B_0. (iii) The aforementioned results are prevalent despite the inclusion of self-gravity in our continuously forced simulations with a mean density similar to the average value of the solar neighbourhood. (iv) Given a fixed B0 and slightly higher mean densities, up to double, the effects of self-gravity are still not qualitatively significant.

  20. Self-Aligned Growth of Organic Semiconductor Single Crystals by Electric Field.

    Science.gov (United States)

    Kotsuki, Kenji; Obata, Seiji; Saiki, Koichiro

    2016-01-19

    We proposed a novel but facile method for growing organic semiconductor single-crystals via solvent vapor annealing (SVA) under electric field. In the conventional SVA growth process, nuclei of crystals appeared anywhere on the substrate and their crystallographic axes were randomly distributed. We applied electric field during the SVA growth of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) on the SiO2/Si substrate on which a pair of electrodes had been deposited beforehand. Real-time observation of the SVA process revealed that rodlike single crystals grew with their long axes parallel to the electric field and bridged the prepatterned electrodes. As a result, C8-BTBT crystals automatically formed a field effect transistor (FET) structure and the mobility reached 1.9 cm(2)/(V s). Electric-field-assisted SVA proved a promising method for constructing high-mobility single-crystal FETs at the desired position by a low-cost solution process.

  1. Distortions of the magnetic field by storm-time current systems in Earth's magnetosphere

    Directory of Open Access Journals (Sweden)

    N. Yu. Ganushkina

    2010-01-01

    Full Text Available Magnetic field and current system changes in Earth's inner magnetosphere during storm times are studied using two principally different modeling approaches: on one hand, the event-oriented empirical magnetic field model, and, on the other, the Space Weather Modeling Framework (SWMF built around a global MHD simulation. Two storm events, one moderate storm on 6–7 November 1997 with Dst minimum about −120 nT and one intense storm on 21–23 October 1999 with Dst minimum about −250 nT were modeled. Both modeling approaches predicted a large ring current (first partial, later symmetric contribution to the magnetic field perturbation for the intense storm. For the moderate storm, the tail current plays a dominant role in the event-oriented model results, while the SWMF results showed no strong tail current in the main phase, which resulted in a poorly timed storm peak relative to the observations. These results imply that the the development of a ring current depends on a strong force to inject the particles deep into the inner magnetosphere, and that the tail current is an important external source for the distortions of the inner magnetospheric magnetic field for both storms. Neither modeling approach was able to reproduce all the variations in the Bx and By components observed at geostationary orbit by GOES satellites during these two storms: the magnetopause current intensifications are inadequate, and the field-aligned currents are not sufficiently represented. While the event-oriented model reproduces rather well the Bz component at geostationary orbit, including the substorm-associated changes, the SWMF field is too dipolar at these locations. The empirical model is a useful tool for validation of the first-principle based models such as the SWMF.

  2. Magnetic field-aligned plasma expansion in critical ionization velocity space experiments

    International Nuclear Information System (INIS)

    Singh, N.

    1989-01-01

    Motivated by the recent Critical Ionization Velocity (CIV) experiments in space, the temporal evolution of a plasma cloud released in an ambient plasma is studied. Time-dependent Vlasov equations for both electrons and ions, along with the Poisson equation for the self-consistent electric field parallel to the ambient magnetic field, are solved. The initial cloud is assumed to consist of cold, warm, and hot electrons with temperatures T/sub c/ ≅ 0.2 eV, T/sub w/ ≅ 2 eV, and T/sub h/ ≅ 10 eV, respectively. It is found that the minor hot electrons escape the cloud, and their velocity distribution function shows the typical time-of-flight dispersion feature - that is, the larger the distance from the cloud, the larger is the average drift velocity of the escaping electrons. The major warm electrons expand along the magnetic field line with the corresponding ion-acoustic speed. The combined effect of the escaping hot electrons and the expanding warm ones sets up an electric potential structure which accelerates the ambient electrons into the cloud. Thus, the energy loss due to the electron escape is partly replenished. The electric field distribution in the potential structure depends on the stage of the evolution; before the rarefaction waves propagating from the edges of the cloud reach its center, the electric fields point into the cloud. After this stage the cloud divides into two subclouds, with each having their own bipolar electric fields. Effects of collisions on the evolution of plasma clouds are also discussed. The relevance of the results seen from the calculations are discussed in the context of recent space experiments on CIV

  3. On the flow magnitude and field-flow alignment at Earth's core surface

    DEFF Research Database (Denmark)

    Finlay, Chris; Amit, H.

    ,with results differing from reference values by less than 8%.Application to a high quality geomagnetic field model based on satelliteobservations (the xCHAOS model in epoch 2004.0) leads to a flowmagnitude estimate of 11 - 14 km / yr, in accordance with previousestimates. When applied to the historical...

  4. Quantitative Evaluation of Remote Field Eddy Current Defect Signals

    International Nuclear Information System (INIS)

    Jeong, Jin Oh; Yi, Jae Kyung; Kim, Hyoung Jean

    2000-01-01

    The remote field eddy current (RFEC) inspection was performed on the ductile cast iron pipes with nominal outer diameter of 100mm, which were machined with various shapes and sizes of defects. Ductile cast iron pipes which are used as water supply pipe have the non-uniform thickness and asymmetric cross section due to relatively high degree of allowable errors during the manufacturing processes. These characteristics of ductile cast in pipes cause the long range background noises in RFEC signals along the pipe. In this study, tile machined defects in pipes were effectively classified by the moving window average (MWA) method which eliminated the long-range noise. The voltage plane polar plots (VPPP) method was used to quantitatively evaluate the depth and circumferential degree of defects. The VPPP signatures showed that the angle between defect signature and the normalized in-phase component on the VPPP is linear to the depth of defects. The nondestructive RFEC technique proved to be capable of quantitatively evaluating the machined defects of underground water supply pipe

  5. The Origin of Radially Aligned Magnetic Fields in Young Supernova Remnants

    Science.gov (United States)

    Inoue, Tsuyoshi; Shimoda, Jiro; Ohira, Yutaka; Yamazaki, Ryo

    2013-08-01

    It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic fields in some young supernova remnants (SNRs) are oriented radially. We study the magnetic field distribution of turbulent SNRs driven by the Richtmyer-Meshkov instability (RMI)—in other words, the effect of rippled shock—by using three-dimensional magnetohydrodynamics simulations. We find that the induced turbulence has radially biased anisotropic velocity dispersion that leads to a selective amplification of the radial component of the magnetic field. The RMI is induced by the interaction between the shock and upstream density fluctuations. Future high-resolution polarization observations can distinguish the following candidates responsible for the upstream density fluctuations: (1) inhomogeneity caused by the cascade of large-scale turbulence in the interstellar medium, the so-called big power-law in the sky; (2) structures generated by the Drury instability in the cosmic-ray modified shock; and (3) fluctuations induced by the nonlinear feedback of the cosmic-ray streaming instability.

  6. Three-dimensional nonlinear ideal MHD equilibria with field-aligned incompressible and compressible flows

    International Nuclear Information System (INIS)

    Moawad, S. M.; Ibrahim, D. A.

    2016-01-01

    The equilibrium properties of three-dimensional ideal magnetohydrodynamics (MHD) are investigated. Incompressible and compressible flows are considered. The governing equations are taken in a steady state such that the magnetic field is parallel to the plasma flow. Equations of stationary equilibrium for both of incompressible and compressible MHD flows are derived and described in a mathematical mode. For incompressible MHD flows, Alfvénic and non-Alfvénic flows with constant and variable magnetofluid density are investigated. For Alfvénic incompressible flows, the general three-dimensional solutions are determined with the aid of two potential functions of the velocity field. For non-Alfvénic incompressible flows, the stationary equilibrium equations are reduced to two differential constraints on the potential functions, flow velocity, magnetofluid density, and the static pressure. Some examples which may be of some relevance to axisymmetric confinement systems are presented. For compressible MHD flows, equations of the stationary equilibrium are derived with the aid of a single potential function of the velocity field. The existence of three-dimensional solutions for these MHD flows is investigated. Several classes of three-dimensional exact solutions for several cases of nonlinear equilibrium equations are presented.

  7. THE ORIGIN OF RADIALLY ALIGNED MAGNETIC FIELDS IN YOUNG SUPERNOVA REMNANTS

    International Nuclear Information System (INIS)

    Inoue, Tsuyoshi; Shimoda, Jiro; Ohira, Yutaka; Yamazaki, Ryo

    2013-01-01

    It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic fields in some young supernova remnants (SNRs) are oriented radially. We study the magnetic field distribution of turbulent SNRs driven by the Richtmyer-Meshkov instability (RMI)—in other words, the effect of rippled shock—by using three-dimensional magnetohydrodynamics simulations. We find that the induced turbulence has radially biased anisotropic velocity dispersion that leads to a selective amplification of the radial component of the magnetic field. The RMI is induced by the interaction between the shock and upstream density fluctuations. Future high-resolution polarization observations can distinguish the following candidates responsible for the upstream density fluctuations: (1) inhomogeneity caused by the cascade of large-scale turbulence in the interstellar medium, the so-called big power-law in the sky; (2) structures generated by the Drury instability in the cosmic-ray modified shock; and (3) fluctuations induced by the nonlinear feedback of the cosmic-ray streaming instability

  8. Alternating current electric fields of varying frequencies: effects on proliferation and differentiation of porcine neural progenitor cells.

    Science.gov (United States)

    Lim, Ji-Hey; McCullen, Seth D; Piedrahita, Jorge A; Loboa, Elizabeth G; Olby, Natasha J

    2013-10-01

    Application of sinusoidal electric fields (EFs) has been observed to affect cellular processes, including alignment, proliferation, and differentiation. In the present study, we applied low-frequency alternating current (AC) EFs to porcine neural progenitor cells (pNPCs) and investigated the effects on cell patterning, proliferation, and differentiation. pNPCs were grown directly on interdigitated electrodes (IDEs) localizing the EFs to a region accessible visually for fluorescence-based assays. Cultures of pNPCs were exposed to EFs (1 V/cm) of 1 Hz, 10 Hz, and 50 Hz for 3, 7, and 14 days and compared to control cultures. Immunocytochemistry was performed to evaluate the expression of neural markers. pNPCs grew uniformly with no evidence of alignment to the EFs and no change in cell numbers when compared with controls. Nestin expression was shown in all groups at 3 and 7 days, but not at 14 days. NG2 expression was low in all groups. Co-expression of glial fibrillary acidic protein (GFAP) and TUJ1 was significantly higher in the cultures exposed to 10- and 50-Hz EFs than the controls. In summary, sinusoidal AC EFs via IDEs did not alter the alignment and proliferation of pNPCs, but higher frequency stimulation appeared to delay differentiation into mature astrocytes.

  9. Axial charge of the weak nucleon current extracted from the β decays of spin aligned 12B and 12N

    International Nuclear Information System (INIS)

    Yamaguchi, Takayuki

    1998-01-01

    The alignment correlation terms in the β-ray angular distributions of the 12 B and 12 N mirror nuclei have been precisely measured, in order to investigate the mesonic effect in the axial charge matrix element. The spin alignments were created with the spin manipulation technique in the β-NMR method, which has been improved based on the recent studies of hyperfine interactions of 12 B and 12 N in a Mg crystal. From the sum of the alignment correlation terms, the ratio of the axial charge to the Gamow-Teller term was determined to be y = 4.66 ± 0.06(stat) ± 0.13(syst). The present result gives clear evidence of the mesonic effect in the axial charge and even more shows 16 ± 6% enhancement over the full calculation which includes the meson exchange effect and the core polarization effect. A possible mass renormalization for the decaying nucleon in a finite nucleon density explains this enhancement. (author)

  10. Aligned Magnetic Field Effects on Flow and Heat Transfer of the Upper-Convected Maxwell Fluid over a Stretching/Shrinking Sheet

    Directory of Open Access Journals (Sweden)

    Waini Iskandar

    2017-01-01

    Full Text Available In this paper, the effect of aligned magnetic field towards the flow and heat transfer of the upper-convected Maxwell (UCM fluid over a stretching/shrinking sheet is numerically studied. The governing partial differential equations are reduced into a system of ordinary differential equations using a similarity transformation, which are then solved numerically using the shooting method. The skin friction and heat transfer coefficients, the velocity, as well as the temperature profiles of the fluid are presented and discussed. Results indicate that an increase in the aligned angle strengthens the applied magnetic field which decrease the velocity and increase the temperature profiles of the fluid. This implies that an increase in the aligned angle increases the skin friction coefficient and decreases the heat transfer coefficients.

  11. Ducting of the Whistler-Mode Waves by Magnetic Field-Aligned Density Enhancements in the Radiation Belt

    Science.gov (United States)

    Streltsov, A. V.; Bengtson, M.; English, D.; Miller, M.; Turco, L.

    2017-12-01

    Whistler-mode waves (or whistlers) are the right-hand polarized electromagnetic waves with a frequency in the range above the lower hybrid frequency and below the electron cyclotron frequency. They can efficiently interact with energetic electrons in the equatorial magnetosphere and remediate them from the earth's radiation belt. These interactions are non-linear, they depend on the wave amplitude, and for them to be efficient the wave power needs to be delivered from the transmitter to the interaction region without significant losses. The main physical mechanism which can solve this problem is ducting/guiding of whistlers by magnetic field-aligned density inhomogeneities or ducts. We present results from a modeling of whistler-mode waves observed by the NASA Van Allen Probes satellites inside the ducts formed by density enhancements (also known as, high-density ducts or HDD). Our previous studies suggest that HDD can confine without leakage only waves with some particular parameters (frequency, perpendicular and parallel wavelength) connected with the parameters of the duct (like duct's "width" and "depth"). Our numerical results confirm that 1) the high-density ducts with amplitudes and perpendicular sizes observed by the RBSP satellites can indeed guide whistlers over significant distances along the ambient magnetic field with small leakage, and 2) the quality of the ducting indeed depends on the wave perpendicular and parallel wavelengths and, therefore, the fact that the wave is ducted by HDD can be used to determine parameters of the wave.

  12. Multiple frequency backscatter observations of heater-induced field-aligned striations in the auroral E region

    International Nuclear Information System (INIS)

    Noble, S.T.

    1985-01-01

    In September 1983 a series of HF ionospheric modification experiments were conducted in Scandinavia using the heat facility near Tromosoe Norway. The purpose of these experiments was to examine the mechanisms by which high-power HF radio waves produce geomagnetic field-aligned striations (FAS) in the auroral E region. The vast majority of the backscatter observations were made with radars operating at 47 and 144 MHz (STARE Finland). Additionally, limited observations were conducted at 140 (STARE Norway) and 21 MHz (SAFARI). These radars are sensitive to irregularities having scale lengths between 1 and 7 m across the geomagnetic field lines. During periods of full power O-mode heating, striations having peak cross sections of 40 to 50 dBsm are observed. Striations are not detected during times of X-mode heating. When the heater output is varied, a corresponding change in the cross section is measured. The magnitude of the change is most pronounced for heater level changes in the range 12.5 to 50% of full power. These cross sections are significantly larger than those measured at midlatitudes using the Arecibo heater (approx.10 1 m 2 ). This is consistent with theoretical studies which indicate that it is easier to excite short-scale FAS at places where the geomagnetic dip angle is large. The growth and decay times of the striations are frequency dependent

  13. Alignment-independent comparison of binding sites based on DrugScore potential fields encoded by 3D Zernike descriptors.

    Science.gov (United States)

    Nisius, Britta; Gohlke, Holger

    2012-09-24

    Analyzing protein binding sites provides detailed insights into the biological processes proteins are involved in, e.g., into drug-target interactions, and so is of crucial importance in drug discovery. Herein, we present novel alignment-independent binding site descriptors based on DrugScore potential fields. The potential fields are transformed to a set of information-rich descriptors using a series expansion in 3D Zernike polynomials. The resulting Zernike descriptors show a promising performance in detecting similarities among proteins with low pairwise sequence identities that bind identical ligands, as well as within subfamilies of one target class. Furthermore, the Zernike descriptors are robust against structural variations among protein binding sites. Finally, the Zernike descriptors show a high data compression power, and computing similarities between binding sites based on these descriptors is highly efficient. Consequently, the Zernike descriptors are a useful tool for computational binding site analysis, e.g., to predict the function of novel proteins, off-targets for drug candidates, or novel targets for known drugs.

  14. Modeling Geoelectric Fields and Geomagnetically Induced Currents Around New Zealand to Explore GIC in the South Island's Electrical Transmission Network

    Science.gov (United States)

    Divett, T.; Ingham, M.; Beggan, C. D.; Richardson, G. S.; Rodger, C. J.; Thomson, A. W. P.; Dalzell, M.

    2017-10-01

    Transformers in New Zealand's South Island electrical transmission network have been impacted by geomagnetically induced currents (GIC) during geomagnetic storms. We explore the impact of GIC on this network by developing a thin-sheet conductance (TSC) model for the region, a geoelectric field model, and a GIC network model. (The TSC is composed of a thin-sheet conductance map with underlying layered resistivity structure.) Using modeling approaches that have been successfully used in the United Kingdom and Ireland, we applied a thin-sheet model to calculate the electric field as a function of magnetic field and ground conductance. We developed a TSC model based on magnetotelluric surveys, geology, and bathymetry, modified to account for offshore sediments. Using this representation, the thin sheet model gave good agreement with measured impedance vectors. Driven by a spatially uniform magnetic field variation, the thin-sheet model results in electric fields dominated by the ocean-land boundary with effects due to the deep ocean and steep terrain. There is a strong tendency for the electric field to align northwest-southeast, irrespective of the direction of the magnetic field. Applying this electric field to a GIC network model, we show that modeled GIC are dominated by northwest-southeast transmission lines rather than east-west lines usually assumed to dominate.

  15. Non-monotonic field dependence of critical current in composite superconductors

    International Nuclear Information System (INIS)

    Andrianov, V.V.; Baev, V.P.; Ivanov, S.S.

    1982-01-01

    The nonmonotonic field dependence of critical current Im(B/sub a/ in composite superconductors is investigated experimentally for current and field varying simultaneously with final rates I and B/sub a/

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

    OpenAIRE

    Petrie, G. J. D.

    2007-01-01

    We consider the potential magnetic field associated with a helical electric line current flow, idealizing the near-potential coronal field within which a highly localized twisted current structure is embedded. It is found that this field has a significant axial component off the helical magnetic axis where there is no current flow, such that the flux winds around the axis. The helical line current field, in including the effects of flux rope writhe, is therefore more topologically complex tha...

  17. Transition from columnar to point pinning in coated conductors: critical currents that are independent of magnetic field direction

    International Nuclear Information System (INIS)

    Zuev, Yuri L; Hun Wee, Sung; Christen, David K

    2012-01-01

    We identify a sharp crossover in the vortex pinning of a high-temperature superconductor with nanocolumnar stacks of precipitates as strong vortex pinning centers. Above a particular, temperature-dependent field B X (T) the vortex response is no longer determined by the nanocolumns, and is instead determined by point-like pinning. This crossover is evident as a change in the dependence of the critical current density on the angle between the applied magnetic field and the nanocolumns. It also leads to the field-orientation-independent power law index n of the E–J curves. Below the transition, there is a strong maximum in J C when the field is aligned parallel to the columns and n depends on field direction. Above the transition, n is independent of the field direction and there is a J C minimum for H parallel to the columns. We discuss a possible mechanism for such behavior change, as well as testing and confirming a prediction that the crossover must become very broad at high temperatures and low fields. (paper)

  18. Resonant fields created by spiral electric currents in Tokamaks

    International Nuclear Information System (INIS)

    Fernandes, A.S.; Caldas, I.L.

    1985-01-01

    The influence of the resonant magnetic perturbations, created by electric currents in spirals, on the plasma confinement in a tokamak with circular section and large aspect ratio is investigated. These perturbations create magnetic islands around the rational magnetic surface which has the helicity of the helicoidal currents. The intensities of these currents are calculated in order to the magnetic islands reach the limiter or others rational surfaces, what could provoke the plasma disrupture. The electric current intensities are estimated, in two spiral sets with different helicities, which create a predominantly stocastic region among the rational magnetic surfaces with these helicities. (L.C.) [pt

  19. Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

    NARCIS (Netherlands)

    Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

    2016-01-01

    Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

  20. Waveguide propagation of electromagnetic waves in high-density ducts aligned along the geomagnetic field in the near-equatorial magnetospheric region

    International Nuclear Information System (INIS)

    Kaufman, R.N.

    1988-01-01

    Waveguide propagation of electromagnetic waves in axial symmetric ducts with increased plasma density aligned along the constant external magnetic field is considered for frequencies, being higher than low-hybrid, in the WKB approximation. In this case tunnel effects leading to captured wave damping are taken into account. Conditions for waveguide propagation and the logarithmic decrement of damping are found. Field construction is performed using the systems of axially symmetric WKB solutions of the Maxwell equations

  1. Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz.

    Science.gov (United States)

    Cao, Yu; Brady, Gerald J; Gui, Hui; Rutherglen, Chris; Arnold, Michael S; Zhou, Chongwu

    2016-07-26

    In this paper, we report record radio frequency (RF) performance of carbon nanotube transistors based on combined use of a self-aligned T-shape gate structure, and well-aligned, high-semiconducting-purity, high-density polyfluorene-sorted semiconducting carbon nanotubes, which were deposited using dose-controlled, floating evaporative self-assembly method. These transistors show outstanding direct current (DC) performance with on-current density of 350 μA/μm, transconductance as high as 310 μS/μm, and superior current saturation with normalized output resistance greater than 100 kΩ·μm. These transistors create a record as carbon nanotube RF transistors that demonstrate both the current-gain cutoff frequency (ft) and the maximum oscillation frequency (fmax) greater than 70 GHz. Furthermore, these transistors exhibit good linearity performance with 1 dB gain compression point (P1dB) of 14 dBm and input third-order intercept point (IIP3) of 22 dBm. Our study advances state-of-the-art of carbon nanotube RF electronics, which have the potential to be made flexible and may find broad applications for signal amplification, wireless communication, and wearable/flexible electronics.

  2. Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2009-07-01

    Full Text Available E region ionospheric modification experiments have been performed at HAARP using pump frequencies about 50 kHz above and below the second electron gyroharmonic frequency. Artificial E region field-aligned plasma density irregularities (FAIs were created and observed using the imaging coherent scatter radar near Homer, Alaska. Echoes from FAIs generated with pump frequencies above and below 2Ωe did not appear to differ significantly in experiments conducted on summer afternoons in 2008, and the resonance instability seemed to be at work in either case. We argue that upper hybrid wave trapping and resonance instability at pump frequencies below the second electron gyroharmonic frequency are permitted theoretically when the effects of finite parallel wavenumbers are considered. Echoes from a sporadic E layer were observed to be somewhat weaker when the pump frequency was 50 kHz below the second electron gyroharmonic frequency. This may indicate that finite parallel wavenumbers are inconsistent with wave trapping in thin sporadic E ionization layers.

  3. Artificial E-region field-aligned plasma irregularities generated at pump frequencies near the second electron gyroharmonic

    Directory of Open Access Journals (Sweden)

    D. L. Hysell

    2009-07-01

    Full Text Available E region ionospheric modification experiments have been performed at HAARP using pump frequencies about 50 kHz above and below the second electron gyroharmonic frequency. Artificial E region field-aligned plasma density irregularities (FAIs were created and observed using the imaging coherent scatter radar near Homer, Alaska. Echoes from FAIs generated with pump frequencies above and below 2Ωe did not appear to differ significantly in experiments conducted on summer afternoons in 2008, and the resonance instability seemed to be at work in either case. We argue that upper hybrid wave trapping and resonance instability at pump frequencies below the second electron gyroharmonic frequency are permitted theoretically when the effects of finite parallel wavenumbers are considered. Echoes from a sporadic E layer were observed to be somewhat weaker when the pump frequency was 50 kHz below the second electron gyroharmonic frequency. This may indicate that finite parallel wavenumbers are inconsistent with wave trapping in thin sporadic E ionization layers.

  4. Minerals and aligned collagen fibrils in tilapia fish scales: structural analysis using dark-field and energy-filtered transmission electron microscopy and electron tomography.

    Science.gov (United States)

    Okuda, Mitsuhiro; Ogawa, Nobuhiro; Takeguchi, Masaki; Hashimoto, Ayako; Tagaya, Motohiro; Chen, Song; Hanagata, Nobutaka; Ikoma, Toshiyuki

    2011-10-01

    The mineralized structure of aligned collagen fibrils in a tilapia fish scale was investigated using transmission electron microscopy (TEM) techniques after a thin sample was prepared using aqueous techniques. Electron diffraction and electron energy loss spectroscopy data indicated that a mineralized internal layer consisting of aligned collagen fibrils contains hydroxyapatite crystals. Bright-field imaging, dark-field imaging, and energy-filtered TEM showed that the hydroxyapatite was mainly distributed in the hole zones of the aligned collagen fibrils structure, while needle-like materials composed of calcium compounds including hydroxyapatite existed in the mineralized internal layer. Dark-field imaging and three-dimensional observation using electron tomography revealed that hydroxyapatite and needle-like materials were mainly found in the matrix between the collagen fibrils. It was observed that hydroxyapatite and needle-like materials were preferentially distributed on the surface of the hole zones in the aligned collagen fibrils structure and in the matrix between the collagen fibrils in the mineralized internal layer of the scale.

  5. Tidal alignment of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  6. Model study of the influence of solar wind parameters on electric currents and fields in middle atmosphere at high latitudes

    International Nuclear Information System (INIS)

    Tonev, P.; Velinov, P.

    2012-01-01

    The electric currents and fields in the strato/mesosphere and lower ionosphere are a result mainly of tropospheric electrical generators (thunderstorms and electrified clouds) which principally determine their global distributions and magnitudes. There are, however, additional sources, e.g. the solar wind (SW), whose contribution to these currents and fields is realized by SW-magnetosphere-ionosphere coupling. This last causes creation of large trans-polar electric potential difference VPC in each polar cap of ∼ 30–140 kV and of horizontal scale ∼ 3000 km which is realized through field-aligned currents (FAC) and is controlled by SW parameters. The potential difference VPC forces formation of closure currents in the dynamo-region. Our study by simulation shows that much smaller currents penetrate into the lower atmospheric regions and influence characteristics of the global atmospheric electrical circuit (GEC). Also, the downward mapping of the horizontal electric fields due to the potential difference VPC leads to creation of very small, but non-negligible vertical electric fields at sea level. They have been demonstrated experimentally as significant (up to few tens of per cent) SW-controlled modifications of the GEC electric characteristics at the ground, at polar latitudes. Our model, based on simulation of Maxwell’s equations in the region 0–160 km under steady-state conditions show that similar but relatively much larger SW-dominated modifications of GEC characteristics take place in the strato/mesosphere and lower ionosphere at polar and high latitudes

  7. Plasmasphere and ring current electric fields observed by GEOS 2

    International Nuclear Information System (INIS)

    Schmidt, R.; Pedersen, A.

    1988-01-01

    The electric field double probe data from GEOS 2 have been statistically examined to study the consecutive passage of the afternoon plasmaspheric bulge and the trough at the geostationary orbit. It was found that the average location of the bulge depends on the magnetic activity and was encountered at earlier local times for higher magnetospheric activity. Within the bulge the electric field showed very frequently a typical directional change from dawnward outside to duskward inside the bulge. The magnitude of the magnetic field was frequently much smaller near the outbound crossing of the plasmaspheric bulge than is expected from a long-term average. The E x B/B-squared drift pointed azimuthally eastward prior to the encounter of the bulge and rotated into the sunward direction within the bulge. Following its passage through the dense, cold plasma in the bulge, GEOS 2 encountered a hot and tenuous plasma sheet-type plasma in the trough that occasionally corrupted the electric field measurements. Generally, the electric field in the trough is much smaller than in the bulge. A possible cause of the sunward plasma flow within the bulge is discussed on the basis of these data. 13 references

  8. Chemical and microbiological effects in the near field: current status

    International Nuclear Information System (INIS)

    Ewart, F.T.; Pugh, S.Y.R.; Wisbey, S.J.; Woodwark, D.R.

    1988-12-01

    The radionuclide inventory of a radioactive waste repository, influenced by the chemical conditions in the near-field, determines the source term for radionuclides entering the geosphere. The research described in this report is focussed on providing the information necessary to quantify this source term. The processes which interact to determine near field behaviour over a long period of time are complex and a simplified representation is required for radiological assessment modelling. The assumptions made in formulating the near field assessment methodology are discussed and justified in this report. The techniques for acquiring the necessary large body of data for a wide range of relevant radionuclides are also described and the values used in the CASCADE I exercise are given. (author)

  9. High current density toroidal pinch discharges with weak toroidal fields

    International Nuclear Information System (INIS)

    Brunsell, P.; Brzozowski, J.; Drake, J.R.; Hellblom, G.; Kaellne, E.; Mazur, S.; Nordlund, P.

    1990-01-01

    Toroidal discharges in the ultralow q regime (ULQ) have been studied in the rebuilt Extrap TI device. ULQ discharges are sustained for pulse lengths exceeding 1 ms, which corresponds to more than 10 resistiv shell times. Values for the safety factor at the vacuum vessel wall are between rational values: 1/(n+1) -2 . The magnetic fluctuation level increases during the transition between rational values of q(a). For very low values of q(a), the loop voltage increases and the toroidal field development in the discharge exhibits the characteristic behaviour of the setting-up phase of a field reversed pinch. (author) 1 ref., 2 figs., 1 tab

  10. Galois and simple current symmetries in conformal field theory

    International Nuclear Information System (INIS)

    Schweigert, C.

    1995-01-01

    In this thesis various aspects of rational field theories are studied. In part I explicit examples for N=2 superconformal field theories are constructed by means of the coset approach. By means of these models string vacua are constructed, and the massless spectra of the string compactifications based on these models are computed. The symmetry of the S matrix, which implements the modular transformation on the space of characters is the subject of Part II. The developed methods are applied to the fusion rings of WZW theories. (HSI)

  11. Current issues in libraries, information science and related fields

    CERN Document Server

    Woodsworth, Anne

    2015-01-01

    This volume is unusual in that the theme is quite broad in scope yet focused on a specific topic; innovations and boundary-pushing studies in areas not usually found in library literature. It examines the periphery of the field surveyed in previous volumes. The chapters are grouped in two categories: professional issues and transforming services.

  12. Comparison of alignment tensors generated for native tRNAVal using magnetic fields and liquid crystalline media

    International Nuclear Information System (INIS)

    Latham, Michael P.; Hanson, Paul; Brown, Darin J.; Pardi, Arthur

    2008-01-01

    Residual dipolar couplings (RDCs) complement standard NOE distance and J-coupling torsion angle data to improve the local and global structure of biomolecules in solution. One powerful application of RDCs is for domain orientation studies, which are especially valuable for structural studies of nucleic acids, where the local structure of a double helix is readily modeled and the orientations of the helical domains can then be determined from RDC data. However, RDCs obtained from only one alignment media generally result in degenerate solutions for the orientation of multiple domains. In protein systems, different alignment media are typically used to eliminate this orientational degeneracy, where the combination of RDCs from two (or more) independent alignment tensors can be used to overcome this degeneracy. It is demonstrated here for native E. coli tRNA Val that many of the commonly used liquid crystalline alignment media result in very similar alignment tensors, which do not eliminate the 4-fold degeneracy for orienting the two helical domains in tRNA. The intrinsic magnetic susceptibility anisotropy (MSA) of the nucleobases in tRNA Val was also used to obtain RDCs for magnetic alignment at 800 and 900 MHz. While these RDCs yield a different alignment tensor, the specific orientation of this tensor combined with the high rhombicity for the tensors in the liquid crystalline media only eliminates two of the four degenerate orientations for tRNA Val . Simulations are used to show that, in optimal cases, the combination of RDCs obtained from liquid crystalline medium and MSA-induced alignment can be used to obtain a unique orientation for the two helical domains in tRNA Val

  13. Current topics and perspectives in the field of radioprotective compounds

    International Nuclear Information System (INIS)

    Sentenac-Roumanou, H.; Fatome, M.

    1978-01-01

    Since discovery, between 1951 and 1955, of the classical radioprotective agents cysteamine, serotonin and A.E.T., synthesis of more active molecules, long acting polymers and compounds active when orally administered, have been performed, especially during the last decade. On the other hand, extensive investigations on mechanism of action of radioprotective agents and particularly discovery of the essential role displayed by protection of the central nervous system of mammals allowed a marked improvement of concepts in the field of chemical radioprotection [fr

  14. Electric fields and currents induced in organs of the human body when exposed to ELF and VLF electromagnetic fields

    Science.gov (United States)

    King, Ronold W. P.; Sandler, Sheldon S.

    1996-09-01

    Formulas for the transverse components of the electric and magnetic fields of the traveling-wave currents of three different types of three-wire, three-phase high-voltage power lines and of a typical VLF transmitter are given. From them, exposure situations for the human body are chosen which permit the analytical determination of the total current induced in that body. With this, the fraction of the total axial current, the axial current density, and the axial electric field in each organ of the body are obtained at any desired cross section. The dimensions and conductivity of these organs must be known. The electric field so obtained is the average macroscopic field in which the cells in each organ are immersed when the whole body is exposed to a known incident field. It corresponds in vivo to the electric field used in vitro to expose cells in tissues.

  15. Field-aligned flows of H+ and He+ in the mid-latitude topside ionosphere at solar maximum

    International Nuclear Information System (INIS)

    Bailey, G.J.; Sellek, R.

    1992-01-01

    A time-dependent mathematical model of the Earth's ionosphere and plasmasphere has been used to investigate the field-aligned flows of H + and He + in the topside ionosphere at L = 3 during solar maximum. When the flux-tube content is low there are upward flows of H + and He + during daytime in both the winter and summer topside ionospheres. During winter night-time the directions of flow are, in general, downwards for He + , because of the night-time decrease in He + scale height, and upwards for H + , because of the replenishment needs of the flux tube. In the winter topside ionosphere, during the later stages of flux-tube replenishment, H + generally flows downwards during both day and night as a result of the greater plasma pressure in the summer hemisphere whilst He + flows upwards during the day and downwards at night. In the summer topside ionosphere H + flows upward to replace the H + lost from the plasmasphere to the winter topside ionosphere whilst the winter helium bulge leads to flows of He + that are in the direction winter hemisphere to summer hemisphere. When the flux-tube content is low, counterstreaming of H + and He + , with H + flowing upwards and He + downwards, occurs for most of the day above about 5000 km altitude in the summer hemisphere. There are occurrences of this type of counterstreaming in both the summer and winter hemispheres during the night. When the flux-tube content is high, counterstreaming of H + and He + occurs less frequently and over smaller regions of the flux tube. There are regions in both hemispheres where H + flows downwards whilst He + flows upwards. (Author)

  16. Morphological study of the field-aligned E-layer irregularities observed by the Gadanki VHF radar

    Directory of Open Access Journals (Sweden)

    C. J. Pan

    2004-11-01

    Full Text Available We report on the field-aligned irregularities observed in the low-latitude sporadic E-layer (Es with the Gadanki (13.5° N, 79.2° E; geomagnetic latitude 6.3° N VHF radar. The radar was operated intermittently for 15 days during the summer months in 1998 and 1999, for both daytime and nighttime observation. The total observation periods are 161h for the nighttime and 68h for the daytime. The observations were used to study the percentage of occurrence of the E-region echoes for both daytime and nighttime. The statistical characteristics of the mean radial velocity and spectral width are presented for three cases based on the echo occurrence characteristics and the altitude of observations (from 90 to 140km ranges, namely, the lower E-region daytime (90-110km, the lower E-region nighttime (90-105km and the upper E-region nighttime (105-140km echoes. The results are compared with that of Piura, a low-latitude station located at about the same geomagnetic latitude, but to the south of the equator. By comparing the behaviors of the lower E-region radar echoes of the summer months between Gadanki and Piura, we find that the lower altitude echoes below about 100km are rarely reported in Piura but commonly seen in Gadanki. Features of the nighttime echoes observed by these two radars are quite similar but daytime FAI echoes are again seldom detected by Piura.

  17. A Method for Eddy Current Field Measurement in Permanent Magnet Magnetic Resonance Imaging Systems

    Directory of Open Access Journals (Sweden)

    SONG Rui

    2018-03-01

    Full Text Available Magnetic resonance imaging (MRI is a widely used medical imaging technique. In MRI system, gradient magnetic fields are used to code spatial information. However, the fast-switching electric currents in the gradients coils used to generate gradient fields also induce vortex electric field, often referred as eddy current, in the surrounding metal conductors. In this paper, a method for eddy current field measurement was proposed. Based on the Faraday law of electromagnetic induction, an eddy current field measuring device was designed. Combining hardware acquisition and software processing, the eddy current field was obtained by subtracting the ideal gradient field from the magnetic field measured experimentally, whose waveform could be displayed in real time. The proposed method was verified by experimental results.

  18. High altitude observations of Birkeland currents

    International Nuclear Information System (INIS)

    Russell, C.T.

    1977-01-01

    Birkeland or field-aligned currents are thought to play a fundamental role in many magnetospheric processes. These roles are reviewed together with observations of Birkeland currents in the distant magnetosphere

  19. Role of work function in field emission enhancement of Au island decorated vertically aligned ZnO nanotapers

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Avanendra [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Senapati, Kartik, E-mail: kartik@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India); Kumar, Mohit; Som, Tapobrata [SUNAG Laboratory, Institute of Physics, Bhubaneswar 751005, Odisha (India); Sinha, Anil K. [Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, M.P. (India); Sahoo, Pratap K., E-mail: pratap.sahoo@niser.ac.in [School of Physical Sciences, National Institute of Science Education and Research (NISER), HBNI, Bhubaneswar 752050, Odisha (India)

    2017-07-31

    Highlights: • Hydrothermally synthesized nanotapers were decorated by gold corrugation using simple evaporation techniques for large area applications. • A significantly enhanced field emission properties of nanotapers were achieved. • The metal induced midgap states formed at the ZnO-Au interface and the reduced effective work function are responsible for low turn-on field. • TUNA measurements revealed a very uniform spatial emission profile in the Au decorated nanotapers. - Abstract: In this report, we demonstrate significantly enhanced field emission properties of ZnO nanotapers achieved via a corrugated decoration of Au. Field emission experiments on these Au-decorated ZnO nanotapers showed emission current densities comparable to the best results in the literature. Au decoration of 5 nm also reduced the effective turn-on field to ∼0.54 V/μm, compared to the as grown ZnO nanotapers, which showed a turn-on field of ∼1.1 V/μm. Tunneling atomic force microscopy measurements revealed a very uniform spatial emission profile in the 5 nm Au decorated nanotapers, which is a basic requirement for any large scale application. We believe that metal induced mid-gap states formed at the ZnO–Au interface are responsible for the observed low turn-on field because such interface states are known to reduce the effective work function. A direct measurement of effective work function using Kelvin probe force microscopy indeed showed more than 1.1 eV drop in the case of 5 nm Au decorated ZnO nanotapers compared to the pristine nanotapers, supporting the above argument.

  20. Relationship between Birkeland current regions, particle precipitation, and electric fields

    International Nuclear Information System (INIS)

    Beaujardiere, O. de la; Watermann, J.; Newell, P.; Rich, F.

    1993-01-01

    The authors study relationships between particle precipitation, currents, and convection, using data from DMSP observations and observations of the Sondrestrom radar. They adopt the classification of Newell et al., who defined five different classes of particle populations observed in satellite crossings of auroral regions. Observations were limited to prenoon local times. The advantage of the DMSP data is that it is part of a consistent 10 year observation mission which provides a broad replicated data set. It is difficult to specify with certainty the polar cap boundary from DMSP data alone

  1. Magnetic field dependence of the critical current density in YBa2Cu3Ox ceramics

    International Nuclear Information System (INIS)

    Zhukov, A.A.; Moshchalkov, V.V.; Komarkov, D.A.; Shabatin, V.P.; Gordeev, S.N.; Shelomov, D.V.

    1989-01-01

    Three magnetic field ranges corresponding to different critical current density j c behavior have been found out. They correlate with grain magnetization changes. The inverse critical current density is shown to depend linearly on the sample cross-section due to the magnetic field induced by the flowing current

  2. Free-standing, well-aligned ordered mesoporous carbon nanofibers on current collectors for high-power micro-supercapacitors.

    Science.gov (United States)

    Kang, Eunae; Jeon, Gumhye; Kim, Jin Kon

    2013-07-21

    The mesoporous carbon nanofiber arrays that stand on carbon-gold double-layer current collectors are synthesized by self-assembly of a PS-b-PEO copolymer and resol in AAO templates for a high-power micro-supercapacitor at high current densities.

  3. Light-cone AdS/CFT-adapted approach to AdS fields/currents, shadows, and conformal fields

    Energy Technology Data Exchange (ETDEWEB)

    Metsaev, R.R. [Department of Theoretical Physics, P.N. Lebedev Physical Institute, Leninsky prospect 53, Moscow 119991 (Russian Federation)

    2015-10-16

    Light-cone gauge formulation of fields in AdS space and conformal field theory in flat space adapted for the study of AdS/CFT correspondence is developed. Arbitrary spin mixed-symmetry fields in AdS space and arbitrary spin mixed-symmetry currents, shadows, and conformal fields in flat space are considered on an equal footing. For the massless and massive fields in AdS and the conformal fields in flat space, simple light-cone gauge actions leading to decoupled equations of motion are found. For the currents and shadows, simple expressions for all 2-point functions are also found. We demonstrate that representation of conformal algebra generators on space of currents, shadows, and conformal fields can be built in terms of spin operators entering the light-cone gauge formulation of AdS fields. This considerably simplifies the study of AdS/CFT correspondence. Light-cone gauge actions for totally symmetric arbitrary spin long conformal fields in flat space are presented. We apply our approach to the study of totally antisymmetric (one-column) and mixed-symmetry (two-column) fields in AdS space and currents, shadows, and conformal fields in flat space.

  4. A high critical current density MOCVD coated conductor with strong vortex pinning centers suitable for very high field use

    International Nuclear Information System (INIS)

    Chen, Z; Kametani, F; Larbalestier, D C; Chen, Y; Xie, Y; Selvamanickam, V

    2009-01-01

    We have made extensive low temperature and high field evaluations of a recent 2.1 μm thick coated conductor (CC) grown by metal-organic chemical vapor deposition (MOCVD) with a view to its use for high field magnet applications, for which its very strong Hastelloy substrate makes it very suitable. This conductor contains dense three-dimensional (Y,Sm) 2 O 3 nanoprecipitates, which are self-aligned in planes tilted ∼7 deg. from the tape plane. Very strong vortex pinning is evidenced by high critical current density J c values of ∼3.1 MA cm -2 at 77 K and ∼43 MA cm -2 at 4.2 K, and by a strongly enhanced irreversibility field H irr , which reaches that of Nb 3 Sn (∼28 T at 1.5 K) at 60 K, even in the inferior direction of H parallel c axis. At 4.2 K, J c values are ∼15% of the depairing current density J d , much the highest of any superconductor suitable for magnet construction.

  5. A high critical current density MOCVD coated conductor with strong vortex pinning centers suitable for very high field use

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Z; Kametani, F; Larbalestier, D C [National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310 (United States); Chen, Y; Xie, Y; Selvamanickam, V [SuperPower Incorporated, Schenectady, NY 12304 (United States)], E-mail: zhijun@asc.magnet.fsu.edu

    2009-05-15

    We have made extensive low temperature and high field evaluations of a recent 2.1 {mu}m thick coated conductor (CC) grown by metal-organic chemical vapor deposition (MOCVD) with a view to its use for high field magnet applications, for which its very strong Hastelloy substrate makes it very suitable. This conductor contains dense three-dimensional (Y,Sm){sub 2}O{sub 3} nanoprecipitates, which are self-aligned in planes tilted {approx}7 deg. from the tape plane. Very strong vortex pinning is evidenced by high critical current density J{sub c} values of {approx}3.1 MA cm{sup -2} at 77 K and {approx}43 MA cm{sup -2} at 4.2 K, and by a strongly enhanced irreversibility field H{sub irr}, which reaches that of Nb{sub 3}Sn ({approx}28 T at 1.5 K) at 60 K, even in the inferior direction of H parallel c axis. At 4.2 K, J{sub c} values are {approx}15% of the depairing current density J{sub d}, much the highest of any superconductor suitable for magnet construction.

  6. Current status on image processing in medical fields in Japan

    International Nuclear Information System (INIS)

    Atsumi, Kazuhiko

    1979-01-01

    Information on medical images are classified in the two patterns. 1) off-line images on films-x-ray films, cell image, chromosome image etc. 2) on-line images detected through sensors, RI image, ultrasonic image, thermogram etc. These images are divided into three characteristic, two dimensional three dimensional and dynamic images. The research on medical image processing have been reported in several meeting in Japan and many fields on images have been studied on RI, thermogram, x-ray film, x-ray-TV image, cancer cell, blood cell, bacteria, chromosome, ultrasonics, and vascular image. Processing on TI image useful and easy because of their digital displays. Software on smoothing, restoration (iterative approximation), fourier transformation, differentiation and subtration. Image on stomach and chest x-ray films have been processed automatically utilizing computer system. Computed Tomography apparatuses have been already developed in Japan and automated screening instruments on cancer cells and recently on blood cells classification have been also developed. Acoustical holography imaging and moire topography have been also studied in Japan. (author)

  7. Acoustic Doppler Current Profiler observations in the southern Caspian Sea: shelf currents and flow field off Feridoonkenar Bay, Iran

    Directory of Open Access Journals (Sweden)

    P. Ghaffari

    2010-07-01

    Full Text Available The results of offshore bottom-mounted ADCP measurements and wind records carried out from August to September 2003 in the coastal waters off Feridoon-kenar Bay (FB in the south Caspian Sea (CS are examined in order to characterize the shelf motion, the steady current field and to determine the main driving forces of currents on the study area. Owing to closed basin and absence of the astronomical tide, the atmospheric forcing plays an important role in the flow field of the CS. The lasting regular sea breeze system is present almost throughout the year. This system performs the forcing in diurnal and semi-diurnal bands similar to tides in other regions. In general, current field in the continental shelf could be separated into two distinguishable schemes, which in cross-shelf direction is dominated by high frequencies (1 cpd and higher frequencies, and in along-shelf orientation mostly proportional to lower frequencies in synoptic weather bands. Long-period wave currents, whose velocities are much greater than those of direct wind-induced currents, dominates the current field in the continental shelf off FB. The propagation of the latter could be described in terms of shore-controlled waves that are remotely generated and travel across the shelf in the southern CS. It has also been shown that long term displacements in this area follow the classic cyclonic, circulation pattern in the southern CS.

  8. High-Throughput Image Analysis of Fibrillar Materials: A Case Study on Polymer Nanofiber Packing, Alignment, and Defects in Organic Field Effect Transistors.

    Science.gov (United States)

    Persson, Nils E; Rafshoon, Joshua; Naghshpour, Kaylie; Fast, Tony; Chu, Ping-Hsun; McBride, Michael; Risteen, Bailey; Grover, Martha; Reichmanis, Elsa

    2017-10-18

    High-throughput discovery of process-structure-property relationships in materials through an informatics-enabled empirical approach is an increasingly utilized technique in materials research due to the rapidly expanding availability of data. Here, process-structure-property relationships are extracted for the nucleation, growth, and deposition of semiconducting poly(3-hexylthiophene) (P3HT) nanofibers used in organic field effect transistors, via high-throughput image analysis. This study is performed using an automated image analysis pipeline combining existing open-source software and new algorithms, enabling the rapid evaluation of structural metrics for images of fibrillar materials, including local orientational order, fiber length density, and fiber length distributions. We observe that microfluidic processing leads to fibers that pack with unusually high density, while sonication yields fibers that pack sparsely with low alignment. This is attributed to differences in their crystallization mechanisms. P3HT nanofiber packing during thin film deposition exhibits behavior suggesting that fibers are confined to packing in two-dimensional layers. We find that fiber alignment, a feature correlated with charge carrier mobility, is driven by increasing fiber length, and that shorter fibers tend to segregate to the buried dielectric interface during deposition, creating potentially performance-limiting defects in alignment. Another barrier to perfect alignment is the curvature of P3HT fibers; we propose a mechanistic simulation of fiber growth that reconciles both this curvature and the log-normal distribution of fiber lengths inherent to the fiber populations under consideration.

  9. Engineering the interface characteristics on the enhancement of field electron emission properties of vertically aligned hexagonal boron nitride nanowalls

    Energy Technology Data Exchange (ETDEWEB)

    Sankaran, K.J.; Hoang, D.Q.; Drijkoningen, S.; Pobedinskas, P.; Haenen, K. [Institute for Materials Research (IMO), Hasselt University, Diepenbeek (Belgium); IMOMEC, IMEC vzw, Diepenbeek (Belgium); Srinivasu, K.; Leou, K.C. [Department of Engineering and System Science, National Tsing Hua University, Hsinchu (China); Korneychuk, S.; Turner, S.; Verbeeck, J. [Electron Microscopy for Materials Science (EMAT), University of Antwerp (Belgium); Lin, I.N. [Department of Physics, Tamkang University, Tamsui (China)

    2016-10-15

    Utilization of Au and nanocrystalline diamond (NCD) as interlayers noticeably modifies the microstructure and field electron emission (FEE) properties of hexagonal boron nitride nanowalls (hBNNWs) grown on Si substrates. The FEE properties of hBNNWs on Au could be turned on at a low turn-on field of 14.3 V μm{sup -1}, attaining FEE current density of 2.58 mA cm{sup -2} and life-time stability of 105 min. Transmission electron microscopy reveals that the Au-interlayer nucleates the hBN directly, preventing the formation of amorphous boron nitride (aBN) in the interface, resulting in enhanced FEE properties. But Au forms as droplets on the Si substrate forming again aBN at the interface. Conversely, hBNNWs on NCD shows superior in life-time stability of 287 min although it possesses inferior FEE properties in terms of larger turn-on field and lower FEE current density as compared to that of hBNNWs-Au. The uniform and continuous NCD film on Si also circumvents the formation of aBN phases and allows hBN to grow directly on NCD. Incorporation of carbon in hBNNWs from the NCD-interlayer improves the conductivity of hBNNWs, which assists in transporting the electrons efficiently from NCD to hBNNWs that results in better field emission of electrons with high life-time stability. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Influence of self-field on the critical current of Bi-2223/Ag tapes

    International Nuclear Information System (INIS)

    Lehtonen, Jorma; Korpela, Aki; Nah, Wansoo; Kang, Joonsun; Kovac, Pavol; Melisek, Tibor

    2004-01-01

    The knowledge of critical current density in a superconducting wire is essential in order to compute AC losses. In HTS tapes the critical current density is difficult to estimate from the measured critical current because self-field tends to reduce the current carrying capacity. In this paper the critical current is measured with a single sample and with two similar samples connected in antiparallel in order to compensate the self-field. Both types of measurement are simulated with finite element method. The simulations help to understand the relation between the measured critical current and material properties. The results suggest that in a high quality tape the self-field effect reduced the measured critical current ∼25% if compared to the real critical current at the zero external field

  11. Experimental search for second-class currents. Beta-ray angular distributions from aligned nuclei /sup 12/B and /sup 12/N

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, K; Minamisono, T; Nojiri, Y; Masuda, Y [Osaka Univ., Toyonaka (Japan). Lab. of Nuclear Studies

    1978-01-01

    The ..beta..-energy dependent angular distributions, W(theta) asymptoticaly equals 1 +- P(1 + ..cap alpha../sub +-/E)P/sub 1/(cos theta) + A..cap alpha../sub +-/EP/sub 2/(cos theta), from the aligned nuclei /sup 12/B and /sup 12/N have been measured. Positive A/sup +/ and negative A/sup -/ alignments were successively produced, by use of NMR, after every other production period of polarized nuclei through nuclear reactions; A/sup +/ - A/sup -/ asymptoticaly equals 0.26 for /sup 12/B and /sup +/A/sup +/ - A/sup - +/ asymptoticaly equals 0.55 for /sup 12/N with p asymptoticaly equals 0. The results are ..cap alpha../sub -/(/sup 12/B) = 0.02/sub 5/ +- 0.03/sub 4/%/MeV, /sup +/..cap alpha../sub +/(/sup 12/N)/sup +/ = 0.27/sub 7/ +- 0.05/sub 2/%/MeV, and ..cap alpha../sub -/ - ..cap alpha../sub +/ = 0.30/sub 2/ +- 0.06/sub 2/%/MeV assuming ..cap alpha../sub +/<0. In comparison with available data for CVC test in the mass-12 triad and theoretical predictions, the present ..cap alpha../sub -/ - ..cap alpha../sub +/ value is consistent within 20% level with predictions of the CVC theory and with absence of second-class induced-tensor currents.

  12. Electric field distribution and current emission in a miniaturized geometrical diode

    Science.gov (United States)

    Lin, Jinpu; Wong, Patrick Y.; Yang, Penglu; Lau, Y. Y.; Tang, W.; Zhang, Peng

    2017-06-01

    We study the electric field distribution and current emission in a miniaturized geometrical diode. Using Schwarz-Christoffel transformation, we calculate exactly the electric field inside a finite vacuum cathode-anode (A-K) gap with a single trapezoid protrusion on one of the electrode surfaces. It is found that there is a strong field enhancement on both electrodes near the protrusion, when the ratio of the A-K gap distance to the protrusion height d /h spot checked against COMSOL simulations. We calculate the effective field enhancement factor for the field emission current, by integrating the local Fowler-Nordheim current density along the electrode surfaces. We systematically examine the electric field enhancement and the current rectification of the miniaturized geometrical diode for various geometric dimensions and applied electric fields.

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

    CERN Document Server

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

    2008-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-21

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

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

    International Nuclear Information System (INIS)

    Garcia-Moral, L.A.; Gomez, G.; Gonzalez-Sanchez, F.J.; Martinez-Rivero, C.; Matorras, F.; Rodrigo, T.; Martinez, P.; Scodellaro, L.; Vila, I.; Virto, A.L.; Sobron, M.; Alberdi, J.; Arce, P.; Barcala, J.M.; Calvo, E.; Ferrando, A.; Josa, M.I.; Molinero, A.; Navarrete, J.; Oller, J.C.

    2009-01-01

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

  16. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    2011-01-01

    The Muon Alignment work now focuses on producing a new track-based alignment with higher track statistics, making systematic studies between the results of the hardware and track-based alignment methods and aligning the barrel using standalone muon tracks. Currently, the muon track reconstruction software uses a hardware-based alignment in the barrel (DT) and a track-based alignment in the endcaps (CSC). An important task is to assess the muon momentum resolution that can be achieved using the current muon alignment, especially for highly energetic muons. For this purpose, cosmic ray muons are used, since the rate of high-energy muons from collisions is very low and the event statistics are still limited. Cosmics have the advantage of higher statistics in the pT region above 100 GeV/c, but they have the disadvantage of having a mostly vertical topology, resulting in a very few global endcap muons. Only the barrel alignment has therefore been tested so far. Cosmic muons traversing CMS from top to bottom are s...

  17. Transport simulations of the oscillating field current drive experiment in the ZT-40M reversed field pinch

    International Nuclear Information System (INIS)

    Scardovelli, R.A.; Nebel, R.A.; Werley, K.A.; Miley, G.H.

    1987-01-01

    Oscillating Field Current Drive (OFCD) is based on the premise that in order to sustain a relaxing Reversed Field Pinch (RFP) plasma, one needs only to supply magnetic helicity at the same rate it is consumed. The purpose of this work is to try to better understand the possible mechanisms underlying these relaxations within the context of different kinds of resistive MHD instabilities

  18. A self-consistent two-dimensional resistive fluid theory of field-aligned potential structures including charge separation and magnetic and velocity shear

    International Nuclear Information System (INIS)

    Hesse, M.; Birn, J.; Schindler, K.

    1990-01-01

    A self-consistent two-fluid theory that includes the magnetic field and shear patterns therein is developed to model stationary electrostatic structures with field-aligned potential drops. Shear flow is also included in the theory since this seems to be a prominent feature of the structures of interest. In addition, Ohmic dissipation, a Hall term and pressure gradients in a generalized Ohm's law, modified for cases without quasi-neutrality are included. In the analytic theory, the electrostatic force is balanced by field-aligned pressure gradients, i.e., thermal effects in the direction of the magnetic field, and by pressure gradients and magnetic stresses in the perpendicular direction. Within this theory simple examples of applications are presented to demonstrate the kind of solutions resulting from the model. The results show how the effects of charge separation and shear in the magnetic field and the velocity can be combined to form self-consistent structures such as are found to exist above the aurora, suggested also in association with solar flares

  19. Simulation of beamline alignment operations

    International Nuclear Information System (INIS)

    Annese, C; Miller, M G.

    1999-01-01

    The CORBA-based Simulator was a Laboratory Directed Research and Development (LDRD) project that applied simulation techniques to explore critical questions about distributed control systems. The simulator project used a three-prong approach that studied object-oriented distribution tools, computer network modeling, and simulation of key control system scenarios. The National Ignition Facility's (NIF) optical alignment system was modeled to study control system operations. The alignment of NIF's 192 beamlines is a large complex operation involving more than 100 computer systems and 8000 mechanized devices. The alignment process is defined by a detailed set of procedures; however, many of the steps are deterministic. The alignment steps for a poorly aligned component are similar to that of a nearly aligned component; however, additional operations/iterations are required to complete the process. Thus, the same alignment operations will require variable amounts of time to perform depending on the current alignment condition as well as other factors. Simulation of the alignment process is necessary to understand beamline alignment time requirements and how shared resources such as the Output Sensor and Target Alignment Sensor effect alignment efficiency. The simulation has provided alignment time estimates and other results based on documented alignment procedures and alignment experience gained in the laboratory. Computer communication time, mechanical hardware actuation times, image processing algorithm execution times, etc. have been experimentally determined and incorporated into the model. Previous analysis of alignment operations utilized average implementation times for all alignment operations. Resource sharing becomes rather simple to model when only average values are used. The time required to actually implement the many individual alignment operations will be quite dynamic. The simulation model estimates the time to complete an operation using

  20. Evolution of Field-Aligned Electron and Ion Densities From Whistler Mode Radio Soundings During Quiet to Moderately Active Period and Comparisons With SAMI2 Simulations

    Science.gov (United States)

    Reddy, A.; Sonwalkar, V. S.; Huba, J. D.

    2018-02-01

    Knowledge of field-aligned electron and ion distributions is necessary for understanding the physical processes causing variations in field-aligned electron and ion densities. Using whistler mode sounding by Radio Plasma Imager/Imager for Magnetopause-to-Aurora Global Exploration (RPI/IMAGE), we determined the evolution of dayside electron and ion densities along L ˜ 2 and L ˜ 3 (90-4,000 km) during a 7 day (21-27 November 2005) geomagnetically quiet to moderately active period. Over this period the O+/H+ transition height was ˜880 ± 60 km and ˜1000 ± 100 km, respectively, at L ˜ 2 and L ˜ 3. The electron density varied in a complex manner; it was different at L ˜ 2 and L ˜ 3 and below and above the O+/H+ transition height. The measured electron and ion densities are consistent with those from Challenging Minisatellite Payload (CHAMP) and Defense Meteorological Satellite Program (DMSP) and other past measurements, but they deviated from bottomside sounding and International Reference Ionosphere (IRI) 2012 empirical model results. Using SAMI2 (Naval Research Laboratory (NRL) ionosphere model) with reasonably adjusted values of inputs (neutral densities, winds, electric fields, and photoelectron heating), we simulated the evolution of O+/H+ transition height and field-aligned electron and ion densities so that a fair agreement was obtained between the simulation results and observations. Simulation studies indicated that reduced neutral densities (H and/or O) with time limited O+-H charge exchange process. This reduction in neutral densities combined with changes in neutral winds and plasma temperature led to the observed variations in the electron and ion densities. The observation/simulation method presented here can be extended to investigate the role of neutral densities and composition, disturbed winds, and prompt penetration electric fields in the storm time ionosphere/plasmasphere dynamics.

  1. Light-cone gauge approach to arbitrary spin fields, currents and shadows

    International Nuclear Information System (INIS)

    Metsaev, R R

    2014-01-01

    Totally symmetric arbitrary spin fields in AdS space, conformal fields, conformal currents, and shadow fields in flat space are studied. Light-cone gauge formulations for such fields, currents and shadows are obtained. Use of the Poincaré parametrization of AdS space and ladder operators allows us to treat fields in flat and AdS spaces on an equal footing. Light-cone gauge realization of relativistic symmetries for fields, currents and shadows is also obtained. The light-cone gauge formulation for fields is obtained by using the gauge invariant Lagrangian which is presented in terms of modified de Donder divergence, while the light-cone gauge formulation for currents and shadows is obtained by using the gauge invariant approach to currents and shadows. This allows us to demonstrate explicitly how the ladder operators entering the gauge invariant formulation of fields, currents and shadows manifest themselves in the light-cone gauge formulation for fields, currents and shadows. (paper)

  2. Initial magnetic field decay of the superconducting magnet in persistent current mode

    International Nuclear Information System (INIS)

    Yamamoto, S.; Yanada, T.

    1988-01-01

    The initial magnetic field decay in the persistent current mode of a magnetic resonance imaging magnet has been studied experimentally. The field decay is greater than the steady field decay due to joint resistances of conductors. Imaging experiments cannot be carried out during the periods, which last ten or more hours. The current distribution in the multifilamentory conductor is non-uniform just after the energization. It is suggested that the change of the current distribution causes the initial magnetic field decay. A 6th order superconducting magnet was prepared for experiments (central field = 0.35 T, inner diameters = 1 m, length = 1.86 m). The steady state magnetic field decay was 7*10/sup -8//hr. The initial magnetic field decay was 3*10/sup -6//hr. Overshoot currents (101 and 105 percent of the rated current) were applied to the magnet and the current reduced to the rated current to improve the initial decay. The energizing and de-energizing rate of the field was 1.8 gauss/second. No initial decay was observed when 105 percent current pattern was applied to the magnet

  3. CHANGE OF MAGNETIC FIELD-GAS ALIGNMENT AT THE GRAVITY-DRIVEN ALFVÉNIC TRANSITION IN MOLECULAR CLOUDS: IMPLICATIONS FOR DUST POLARIZATION OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Che-Yu; King, Patrick K.; Li, Zhi-Yun [Department of Astronomy, University of Virginia, Charlottesville, VA 22901 (United States)

    2016-10-01

    Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields, whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this transition, we compute the histogram of relative orientation (HRO) between the density gradient and the magnetic field in three-dimensional magnetohydrodynamic (MHD) simulations of prestellar core formation in shock-compressed regions within giant molecular clouds. We find that, in the magnetically dominated (sub-Alfvénic) post-shock region, the gas structure is preferentially aligned with the local magnetic field. For overdense sub-regions with super-Alfvénic gas, their elongation becomes preferentially perpendicular to the local magnetic field. The transition occurs when self-gravitating gas gains enough kinetic energy from the gravitational acceleration to overcome the magnetic support against the cross-field contraction, which results in a power-law increase of the field strength with density. Similar results can be drawn from HROs in projected two-dimensional maps with integrated column densities and synthetic polarized dust emission. We quantitatively analyze our simulated polarization properties, and interpret the reduced polarization fraction at high column densities as the result of increased distortion of magnetic field directions in trans- or super-Alfvénic gas. Furthermore, we introduce measures of the inclination and tangledness of the magnetic field along the line of sight as the controlling factors of the polarization fraction. Observations of the polarization fraction and angle dispersion can therefore be utilized in studying local magnetic field morphology in star-forming regions.

  4. Research of the voltage and current stabilization processes by using the silicon field-effect transistor

    International Nuclear Information System (INIS)

    Karimov, A.V.; Yodgorova, D.M.; Kamanov, B.M.; Giyasova, F.A.; Yakudov, A.A.

    2012-01-01

    The silicon field-effect transistors were investigated to use in circuits for stabilization of current and voltage. As in gallium arsenide field-effect transistors, in silicon field-effect transistors with p-n-junction a new mechanism of saturation of the drain current is experimentally found out due to both transverse and longitudinal compression of channel by additional resistance between the source and the gate of the transistor. The criteria for evaluating the coefficients of stabilization of transient current suppressors and voltage stabilizator based on the field-effect transistor are considered. (authors)

  5. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G. Gomez

    Since December, the muon alignment community has focused on analyzing the data recorded so far in order to produce new DT and CSC Alignment Records for the second reprocessing of CRAFT data. Two independent algorithms were developed which align the DT chambers using global tracks, thus providing, for the first time, a relative alignment of the barrel with respect to the tracker. These results are an important ingredient for the second CRAFT reprocessing and allow, for example, a more detailed study of any possible mis-modelling of the magnetic field in the muon spectrometer. Both algorithms are constructed in such a way that the resulting alignment constants are not affected, to first order, by any such mis-modelling. The CSC chambers have not yet been included in this global track-based alignment due to a lack of statistics, since only a few cosmics go through the tracker and the CSCs. A strategy exists to align the CSCs using the barrel as a reference until collision tracks become available. Aligning the ...

  6. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    Gervasio Gomez

    The main progress of the muon alignment group since March has been in the refinement of both the track-based alignment for the DTs and the hardware-based alignment for the CSCs. For DT track-based alignment, there has been significant improvement in the internal alignment of the superlayers inside the DTs. In particular, the distance between superlayers is now corrected, eliminating the residual dependence on track impact angles, and good agreement is found between survey and track-based corrections. The new internal geometry has been approved to be included in the forthcoming reprocessing of CRAFT samples. The alignment of DTs with respect to the tracker using global tracks has also improved significantly, since the algorithms use the latest B-field mapping, better run selection criteria, optimized momentum cuts, and an alignment is now obtained for all six degrees of freedom (three spatial coordinates and three rotations) of the aligned DTs. This work is ongoing and at a stage where we are trying to unders...

  7. Analytical theory of neutral current sheets with a sheared magnetic field in collisionless relativistic plasma

    Science.gov (United States)

    Kocharovsky, V. V.; Kocharovsky, Vl V.; Martyanov, V. Yu; Nechaev, A. A.

    2017-12-01

    We derive and describe analytically a new wide class of self-consistent magnetostatic structures with sheared field lines and arbitrary energy distributions of particles. To do so we analyze superpositions of two planar current sheets with orthogonal magnetic fields and cylindrically symmetric momentum distribution functions, such that the magnetic field of one of them is directed along the symmetry axis of the distribution function of the other. These superpositions satisfy the pressure balance equation and allow one to construct configurations with an almost arbitrarily sheared magnetic field. We show that most of previously known current sheet families with sheared magnetic field lines are included in this novel class.

  8. Measurement and interpretation of current transmission in a crossed-field diode below cutoff

    International Nuclear Information System (INIS)

    Vanderberg, B.H.; Eninger, J.E.

    1997-01-01

    Measurements on the current-voltage-magnetic field characteristics of a space-charge-limited cylindrical cross-field diode below cutoff are presented. The measured current is found to be lower than predicted by simple cold-fluid theory. This reduction combined with observed oscillations in the current can be explained by secondary electron emission from the anode, leading to an increase of space charge in the diode. copyright 1997 American Institute of Physics

  9. Method for confining the magnetic field of the cross-tail current inside the magnetopause

    Science.gov (United States)

    Sotirelis, T.; Tsyganenko, N. A.; Stern, D. P.

    1994-01-01

    A method is presented for analytically representing the magnetic field due to the cross-tail current and its closure on the magnetopause. It is an extension of a method used by Tsyganenko (1989b) to confine the dipole field inside an ellipsoidal magnetopause using a scalar potential. Given a model of the cross-tail current, the implied net magnetic field is obtained by adding to the cross-tail current field a potential field B = - del gamma, which makes all field lines divide into two disjoint groups, separated by the magnetopause (i.e., the combined field is made to have zero normal component with the magnetopause). The magnetopause is assumed to be an ellipsoid of revolution (a prolate spheroid) as an approximation to observations (Sibeck et al., 1991). This assumption permits the potential gamma to be expressed in spheroidal coordinates, expanded in spheroidal harmonics and its terms evaluated by performing inversion integrals. Finally, the field outside the magnetopause is replaced by zero, resulting in a consistent current closure along the magnetopause. This procedure can also be used to confine the modeled field of any other interior magnetic source, though the model current must always flow in closed circuits. The method is demonstrated on the T87 cross-tail current, examples illustrate the effect of changing the size and shape of the prescribed magnetopause and a comparison is made to an independent numerical scheme based on the Biot-Savart equation.

  10. MUON DETECTORS: ALIGNMENT

    CERN Multimedia

    G.Gomez

    Since September, the muon alignment system shifted from a mode of hardware installation and commissioning to operation and data taking. All three optical subsystems (Barrel, Endcap and Link alignment) have recorded data before, during and after CRAFT, at different magnetic fields and during ramps of the magnet. This first data taking experience has several interesting goals: •    study detector deformations and movements under the influence of the huge magnetic forces; •    study the stability of detector structures and of the alignment system over long periods, •    study geometry reproducibility at equal fields (specially at 0T and 3.8T); •    reconstruct B=0T geometry and compare to nominal/survey geometries; •    reconstruct B=3.8T geometry and provide DT and CSC alignment records for CMSSW. However, the main goal is to recons...

  11. Representation theory of current algebra and conformal field theory on Riemann surfaces

    International Nuclear Information System (INIS)

    Yamada, Yasuhiko

    1989-01-01

    We study conformal field theories with current algebra (WZW-model) on general Riemann surfaces based on the integrable representation theory of current algebra. The space of chiral conformal blocks defined as solutions of current and conformal Ward identities is shown to be finite dimensional and satisfies the factorization properties. (author)

  12. Estimation of electric fields and currents from International Magnetospheric Study magnetometer data for the CDAW 6 intervals: Implications for substorm dynamics

    International Nuclear Information System (INIS)

    Kamide, Y.; Baumjohann, W.

    1985-01-01

    Using a recently developed numerical scheme combined with International Magnetospheric Study magnetometer data and the Rice University Ionospheric conductivity model as input, the global distribution of the key ionospheric parameters is estimated for the Coordinated Data Analysis Workshop (CDAW) 6 intervals. These outputs include ionospheric electric fields and currents, field-aligned currents and Joule heat production rate at high latitudes, and are compiled in the form of a color movie film, which demonstrates dynamics of substorm changes of the three-dimensional current system as well as of the associated potential pattern. The present paper gives, on the basis of the space-time distribution of the key parameters, the substorm time frame that can be referenced to in terms of the substorm phases when discussing some other magnetospheric and ionospheric records. The distinction between ''substorm expansion'' and ''enhanced convection'' current systems is presented on the basis of the conventional equivalent current and potential patterns and ''true'' ionospheric currents. Although the auroral electrojets flow rather contiguously throughout the dark sector, there are several separate source regions of Joule heating from the electrojet currents. This indicates that the relative importance of the ionospheric conductivity and the electric field in the ionospheric currents varies considerably depending upon latitude and local time. A possible difference in the generation mechanisms of isolated and continuous substorm activity is also discussed to some extent in the light of the two CDAW 6 intervals

  13. A 3.5 V lithium-iodine hybrid redox battery with vertically aligned carbon nanotube current collector.

    Science.gov (United States)

    Zhao, Yu; Hong, Misun; Bonnet Mercier, Nadège; Yu, Guihua; Choi, Hee Cheul; Byon, Hye Ryung

    2014-02-12

    A lithium-iodine (Li-I2) cell using the triiodide/iodide (I3(-)/I(-)) redox couple in an aqueous cathode has superior gravimetric and volumetric energy densities (∼ 330 W h kg(-1) and ∼ 650 W h L(-1), respectively, from saturated I2 in an aqueous cathode) to the reported aqueous Li-ion batteries and aqueous cathode-type batteries, which provides an opportunity to construct cost-effective and high-performance energy storage. To apply this I3(-)/I(-) aqueous cathode for a portable and compact 3.5 V battery, unlike for grid-scale storage as general target of redox flow batteries, we use a three-dimensional and millimeter thick carbon nanotube current collector for the I3(-)/I(-) redox reaction, which can shorten the diffusion length of the redox couple and provide rapid electron transport. These endeavors allow the Li-I2 battery to enlarge its specific capacity, cycling retention, and maintain a stable potential, thereby demonstrating a promising candidate for an environmentally benign and reusable portable battery.

  14. High Field Side Lower Hybrid Current Drive Simulations for Off- axis Current Drive in DIII-D

    Directory of Open Access Journals (Sweden)

    Wukitch S.J.

    2017-01-01

    Full Text Available Efficient off-axis current drive scalable to reactors is a key enabling technology for developing economical, steady state tokamak. Previous studies have focussed on high field side (HFS launch of lower hybrid current drive (LHCD in double null configurations in reactor grade plasmas and found improved wave penetration and high current drive efficiency with driven current profile peaked near a normalized radius, ρ, of 0.6-0.8, consistent with advanced tokamak scenarios. Further, HFS launch potentially mitigates plasma material interaction and coupling issues. For this work, we sought credible HFS LHCD scenario for DIII-D advanced tokamak discharges through utilizing advanced ray tracing and Fokker Planck simulation tools (GENRAY+CQL3D constrained by experimental considerations. For a model and existing discharge, HFS LHCD scenarios with excellent wave penetration and current drive were identified. The LHCD is peaked off axis, ρ∼0.6-0.8, with FWHM Δρ=0.2 and driven current up to 0.37 MA/MW coupled. For HFS near mid plane launch, wave penetration is excellent and have access to single pass absorption scenarios for variety of plasmas for n||=2.6-3.4. These DIII-D discharge simulations indicate that HFS LHCD has potential to demonstrate efficient off axis current drive and current profile control in DIII-D existing and model discharge.

  15. Contribution of Field Strength Gradients to the Net Vertical Current of Active Regions

    Science.gov (United States)

    Vemareddy, P.

    2017-12-01

    We examined the contribution of field strength gradients for the degree of net vertical current (NVC) neutralization in active regions (ARs). We used photospheric vector magnetic field observations of AR 11158 obtained by Helioseismic and Magnetic Imager on board SDO and Hinode. The vertical component of the electric current is decomposed into twist and shear terms. The NVC exhibits systematic evolution owing to the presence of the sheared polarity inversion line between rotating and shearing magnetic regions. We found that the sign of shear current distribution is opposite in dominant pixels (60%–65%) to that of twist current distribution, and its time profile bears no systematic trend. This result indicates that the gradient of magnetic field strength contributes to an opposite signed, though smaller in magnitude, current to that contributed by the magnetic field direction in the vertical component of the current. Consequently, the net value of the shear current is negative in both polarity regions, which when added to the net twist current reduces the direct current value in the north (B z > 0) polarity, resulting in a higher degree of NVC neutralization. We conjecture that the observed opposite signs of shear and twist currents are an indication, according to Parker, that the direct volume currents of flux tubes are canceled by their return currents, which are contributed by field strength gradients. Furthermore, with the increase of spatial resolution, we found higher values of twist, shear current distributions. However, the resolution effect is more useful in resolving the field strength gradients, and therefore suggests more contribution from shear current for the degree of NVC neutralization.

  16. Strain dependence of the critical current and critical field in multifilamentary Nb3Sn composites

    International Nuclear Information System (INIS)

    Ekin, J.W.

    1979-01-01

    High-J/sub c/ multifilamentary Nb 3 Sn superconductors with widely varying amounts of prestrain and critical field values can be characterized fairly accurately by a single normalized critical field-strain relationship. Such a relationship permits first order prediction of critical-current degradation at arbitrary magnetic field magnitudes with knowledge of only two parameters for any conductor, the prestrain and the maximum critical field. Some of the conductor-fabrication factors affecting the parameters are considered

  17. New overlay measurement technique with an i-line stepper using embedded standard field image alignment marks for wafer bonding applications

    Science.gov (United States)

    Kulse, P.; Sasai, K.; Schulz, K.; Wietstruck, M.

    2017-06-01

    marks. In this work, the non-contact infrared alignment system of the Nikon i-line Stepper NSR-SF150 for both the alignment and the overlay determination of bonded wafer stacks with embedded alignment marks are used to achieve an accurate alignment between the different wafer sides. The embedded field image alignment (FIA) marks of the interface and the device wafer top layer are measured in a single measurement job. By taking the offsets between all different FIA's into account, after correcting the wafer rotation induced FIA position errors, hence an overlay for the stacked wafers can be determined. The developed approach has been validated by a standard back to front side application. The overlay was measured and determined using both, the EVG NT40 automated measurement system with special overlay marks and the measurement of the FIA marks of the front and back side layer. A comparison of both results shows mismatches in x and y translations smaller than 200 nm, which is relatively small compared to the overlay tolerances of +/-500 nm for the back to front side process. After the successful validation of the developed technique, special wafer stacks with FIA alignment marks in the bonding interface are fabricated. Due to the super IR light transparency of both doubled side polished wafers, the embedded FIA marks generate a stable and clear signal for accurate x and y wafer coordinate positioning. The FIA marks of the device wafer top layer were measured under standard condition in a developed photoresist mask without IR illumination. Following overlay calculation shows an overlay of less than 200 nm, which enables very accurate process condition for highly scaled TSV integration and advanced substrate integration into IHP's 0.25/0.13 μm SiGe:C BiCMOS technology. The presented method can be applied for both the standard back to front side process technologies and also new temporary and permanent wafer bonding applications.

  18. Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

    DEFF Research Database (Denmark)

    Lühr, Hermann; Xiong, Chao; Olsen, Nils

    2017-01-01

    . Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling...... its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing......Magnetospheric currents play an important role in the electrodynamics of near-Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field...

  19. Magnetic Field Dependence of the Critical Current in S-N Bilayer Thin Films

    Science.gov (United States)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen James; Bandler, Simon; Chervenak, James; Kilbourne, Caroline A.; Finkbeiner, Fred M.; Porter, Frederick S.; Kelley, Richard L.; Adams, Joseph S.; hide

    2013-01-01

    Here we investigate the effects a non-uniform applied magnetic field has on superconducting transition-edge sensors (TESs) critical current. This has implications on TES optimization. It has been shown that TESs resistive transition can be altered by magnetic fields. We have observed critical current rectification effects and explained these effects in terms of a magnetic self-field arising from asymmetric current injection into the sensor. Our TES physical model shows that this magnetic self-field can result in significantly degraded or improved TES performance. In order for this magnetically tuned TES strategy to reach its full potential we are investigating the effect a non-uniform applied magnetic field has on the critical current.

  20. The degrees of tri-axial orientation in RE-doped Bi2212 powders aligned in a modulated rotation magnetic field

    International Nuclear Information System (INIS)

    Nagai, R.; Horii, S.; Maeda, T.; Haruta, M.; Shimoyama, J.

    2013-01-01

    Highlights: •Tri-axial magnetic alignment of Bi2212 with rare-earth (RE) doping was attempted. •Magnetization axes depended on the type of doped RE ions. •RE-doping increased degrees of inplane orientation and inplane magnetic anisotropy. -- Abstract: We report relationship between the degrees of tri-axial orientation and doping level of rare earth (RE) ions in Bi 2 Sr 2 (Ca 1−x RE x )Cu 2 O y (RE-doped Bi2212; RE = Dy, Ho, Er and Tm) powder samples aligned under a modulated rotation magnetic field (MRF) of 10 T. Tri-axial magnetic alignment of the RE-doped Bi2212 with x = 0–0.5 was achieved by single-ion magnetic anisotropy of RE 3+ and tri-axial magnetic anisotropy induced by modulation microstructure in a grain level. The degrees of in-plane and c-axis orientation with ∼3° were achieved for the case of the Tm-doped Bi2212 with x = 0.5. The findings in the present study give us important information for the fabrication of triaxially oriented Bi-based cuprate superconductor materials by the magneto-scientific process

  1. Transient interaction model of electromagnetic field generated by lightning current pulses and human body

    International Nuclear Information System (INIS)

    Iváncsy, T; Kiss, I; Tamus, Z Á; Szücs, L

    2015-01-01

    The lightning current generates time-varying magnetic field near the down-conductor and the down-conductors are mounted on the wall of the buildings where residential places might be situated. It is well known that the rapidly changing magnetic fields can generate dangerous eddy currents in the human body.The higher duration and gradient of the magnetic field can cause potentially life threatening cardiac stimulation. The coupling mechanism between the electromagnetic field and the human body is based on a well-known physical phenomena (e.g. Faradays law of induction). However, the calculation of the induced current is very complicated because the shape of the organs is complex and the determination of the material properties of living tissues is difficult, as well. Our previous study revealed that the cardiac stimulation is independent of the rising time of the lightning current and only the peak of the current counts.In this study, the authors introduce an improved model of the interaction of electromagnetic fields of lighting current near down-conductor and human body. Our previous models are based on the quasi stationer field calculations, the new improved model is a transient model. This is because the magnetic field around the down-conductor and in the human body can be determined more precisely, therefore the dangerous currents in the body can be estimated. (paper)

  2. Magnetic field dependence of the critical superconducting current induced by the proximity effect in silicon

    International Nuclear Information System (INIS)

    Nishino, T.; Kawabe, U.; Yamada, E.

    1986-01-01

    The magnetic field dependence of the critical superconducting current induced by the proximity effect in heavily-boron-doped Si is studied experimentally. It is found that the critical current flowing through the p-type-Si-coupled junction decreases with increasing applied magnetic field. The critical current can be expressed as the product of three factors: the current induced by de Gennes's proximity effect, the exponential decrease due to pair breaking by the magnetic field, and the usual diffraction-pattern-like dependence on the magnetic field due to the Josephson effect. The second factor depends on the carrier concentration in the semiconductor. The local critical current shows a rapid decrease at the edge of the electrodes

  3. Topological currents in neutron stars: kicks, precession, toroidal fields, and magnetic helicity

    International Nuclear Information System (INIS)

    Charbonneau, James; Zhitnitsky, Ariel

    2010-01-01

    The effects of anomalies in high density QCD are striking. We consider a direct application of one of these effects, namely topological currents, on the physics of neutron stars. All the elements required for topological currents are present in neutron stars: degenerate matter, large magnetic fields, and parity violating processes. These conditions lead to the creation of vector currents capable of carrying momentum and inducing magnetic fields. We estimate the size of these currents for many representative states of dense matter in the neutron star and argue that they could be responsible for the large proper motion of neutron stars (kicks), the toroidal magnetic field and finite magnetic helicity needed for stability of the poloidal field, and the resolution of the conflict between type-II superconductivity and precession. Though these observational effects appear unrelated, they likely originate from the same physics — they are all P-odd phenomena that stem from a topological current generated by parity violation

  4. Variations of plasmaspheric field-aligned electron and ion densities (90-4000 km) during quiet to moderately active (Kp < 4) geomagnetic conditions

    Science.gov (United States)

    Sonwalkar, V. S.; Reddy, A.

    2017-12-01

    Variation in field-aligned electron and ion densities as a function of geomagnetic activity are important parameters in the physics of the thermosphere-ionosphere-magnetosphere coupling. Using whistler mode sounding from IMAGE, we report variations in field-aligned electron density and O+/H+ transition height (HT) during two periods (16-23 Aug 2005; 24 Sep-06 Oct 2005) when geomagnetic conditions were quiet (maximum Kp in the past 24 hours, Kpmax,24 ≤ 2) to moderately active (2 quiet time, during moderate geomagnetic activity: (1) O+/H+ transition height was roughly same; (2) electron density variations below HT showed no trend; (3) electron density above HT increased ( 10-40 %). The measured electron density is in agreement with in situ measurements from CHAMP (350 km) and DMSP (850 km) and past space borne (e. g., ISIS) measurements but the F2 peak density is a factor of 2 lower relative to that measured by ground ionosondes and that predicted by IRI-2012 empirical model. The measured transition height is consistent with OGO 4, Explorer 31, and C/NOFS measurements but is lower than that from IRI-2012. The observed variations in electron density at F2 peak are consistent with past work and are attributed to solar, geomagnetic, and meteorological causes [e. g. Risibeth and Mendillo, 2001; Forbes et al., 2000]. To the best of our knowledge, variations in field-aligned electron density above transition height at mid-latitudes during quiet to moderately active periods have not been reported in the past. Further investigation using physics based models (e. g., SAMI3) is required to explain the observed variations.

  5. Coronal Heating Topology: The Interplay of Current Sheets and Magnetic Field Lines

    Energy Technology Data Exchange (ETDEWEB)

    Rappazzo, A. F.; Velli, M. [Department of Earth, Planetary, and Space Sciences, UCLA, Los Angeles, CA 90095 (United States); Matthaeus, W. H. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Ruffolo, D. [Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand); Servidio, S., E-mail: rappazzo@ucla.edu [Dipartimento di Fisica, Università della Calabria, Cosenza I-87036 (Italy)

    2017-07-20

    The magnetic topology and field line random walk (FLRW) properties of a nanoflare-heated and magnetically confined corona are investigated in the reduced magnetohydrodynamic regime. Field lines originating from current sheets form coherent structures, called current sheet connected (CSC) regions, which extend around them. CSC FLRW is strongly anisotropic, with preferential diffusion along the current sheets’ in-plane length. CSC FLRW properties remain similar to those of the entire ensemble but exhibit enhanced mean square displacements and separations due to the stronger magnetic field intensities in CSC regions. The implications for particle acceleration and heat transport in the solar corona and wind, and for solar moss formation are discussed.

  6. Photocurrent, Rectification, and Magnetic Field Symmetry of Induced Current Through Quantum Dots

    DEFF Research Database (Denmark)

    DiCarlo, L.; M. Marcus, C.; Harris jr, J.

    2003-01-01

    We report mesoscopic dc current generation in an open chaotic quantum dot with ac excitation applied to one of the shape-defining gates. For excitation frequencies large compared to the inverse dwell time of electrons in the dot (i.e., GHz), we find mesoscopic fluctuations of induced current...... that are fully asymmetric in the applied perpendicular magnetic field, as predicted by recent theory. Conductance, measured simultaneously, is found to be symmetric in field. In the adiabatic (i.e., MHz) regime, in contrast, the induced current is always symmetric in field, suggesting its origin is mesoscopic...

  7. Aligned Magnetic Field, Radiation, and Rotation Effects on Unsteady Hydromagnetic Free Convection Flow Past an Impulsively Moving Vertical Plate in a Porous Medium

    Directory of Open Access Journals (Sweden)

    Sandeep Naramgari

    2014-01-01

    Full Text Available We analyse the effects of aligned magnetic field, radiation, and rotation on unsteady hydromagnetic free convection flow of a viscous incompressible electrically conducting fluid past an impulsively moving vertical plate in a porous medium in presence of heat source. An exact solution of the governing equations in dimensionless form is obtained by Laplace transform technique in ramped temperature case. To compare the results obtained in this case with that of isothermal plate, the exact solution of the governing equations is also obtained for isothermal plate and results are discussed graphically in both ramped temperature and isothermal cases.

  8. Clear aligners in orthodontic treatment.

    Science.gov (United States)

    Weir, T

    2017-03-01

    Since the introduction of the Tooth Positioner (TP Orthodontics) in 1944, removable appliances analogous to clear aligners have been employed for mild to moderate orthodontic tooth movements. Clear aligner therapy has been a part of orthodontic practice for decades, but has, particularly since the introduction of Invisalign appliances (Align Technology) in 1998, become an increasingly common addition to the orthodontic armamentarium. An internet search reveals at least 27 different clear aligner products currently on offer for orthodontic treatment. The present paper will highlight the increasing popularity of clear aligner appliances, as well as the clinical scope and the limitations of aligner therapy in general. Further, the paper will outline the differences between the various types of clear aligner products currently available. © 2017 Australian Dental Association.

  9. Dynamics of Ring Current and Electric Fields in the Inner Magnetosphere During Disturbed Periods: CRCM-BATS-R-US Coupled Model

    Science.gov (United States)

    Buzulukova, N.; Fok, M.-C.; Pulkkinen, A.; Kuznetsova, M.; Moore, T. E.; Glocer, A.; Brandt, P. C.; Toth, G.; Rastaetter, L.

    2010-01-01

    We present simulation results from a one-way coupled global MHD model (Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme, BATS-R-US) and kinetic ring current models (Comprehensive Ring Current Model, CRCM, and Fok Ring Current, FokRC). The BATS-R-US provides the CRCM/FokRC with magnetic field information and plasma density/temperature at the polar CRCM/FokRC boundary. The CRCM uses an electric potential from the BATS-R-US ionospheric solver at the polar CRCM boundary in order to calculate the electric field pattern consistent with the CRCM pressure distribution. The FokRC electric field potential is taken from BATS-R-US ionospheric solver everywhere in the modeled region, and the effect of Region II currents is neglected. We show that for an idealized case with southward-northward-southward Bz IMF turning, CRCM-BATS-R-US reproduces well known features of inner magnetosphere electrodynamics: strong/weak convection under the southward/northward Bz; electric field shielding/overshielding/penetration effects; an injection during the substorm development; Subauroral Ion Drift or Polarization Jet (SAID/PJ) signature in the dusk sector. Furthermore, we find for the idealized case that SAID/PJ forms during the substorm growth phase, and that substorm injection has its own structure of field-aligned currents which resembles a substorm current wedge. For an actual event (12 August 2000 storm), we calculate ENA emissions and compare with Imager for Magnetopause-to-Aurora Global Exploration/High Energy Neutral Atom data. The CRCM-BATS-R-US reproduces both the global morphology of ring current and the fine structure of ring current injection. The FokRC-BATS-R-US shows the effect of a realistic description of Region II currents in ring current-MHD coupled models.

  10. Near-Earth Magnetic Field Effects of Large-Scale Magnetospheric Currents

    Science.gov (United States)

    Luehr, Hermann; Xiong, Chao; Olsen, Nils; Le, Guan

    2016-01-01

    Magnetospheric currents play an important role in the electrodynamics of near- Earth space. This has been the topic of many space science studies. Here we focus on the magnetic fields they cause close to Earth. Their contribution to the geomagnetic field is the second largest after the core field. Significant progress in interpreting the magnetic fields from the different sources has been achieved thanks to magnetic satellite missions like Ørsted, CHAMP and now Swarm. Of particular interest for this article is a proper representation of the magnetospheric ring current effect. Uncertainties in modelling its effect still produce the largest residuals between observations and present-day geomagnetic field models. A lot of progress has been achieved so far, but there are still open issues like the characteristics of the partial ring current. Other currents discussed are those flowing in the magnetospheric tail. Also their magnetic contribution at LEO orbits is non-negligible. Treating them as an independent source is a more recent development, which has cured some of the problems in geomagnetic field modelling. Unfortunately there is no index available for characterizing the tail current intensity. Here we propose an approach that may help to properly quantify the magnetic contribution from the tail current for geomagnetic field modelling. Some open questions that require further investigation are mentioned at the end.

  11. The morphological and molecular changes of brain cells exposed to direct current electric field stimulation.

    Science.gov (United States)

    Pelletier, Simon J; Lagacé, Marie; St-Amour, Isabelle; Arsenault, Dany; Cisbani, Giulia; Chabrat, Audrey; Fecteau, Shirley; Lévesque, Martin; Cicchetti, Francesca

    2014-12-07

    The application of low-intensity direct current electric fields has been experimentally used in the clinic to treat a number of brain disorders, predominantly using transcranial direct current stimulation approaches. However, the cellular and molecular changes induced by such treatment remain largely unknown. Here, we tested various intensities of direct current electric fields (0, 25, 50, and 100V/m) in a well-controlled in vitro environment in order to investigate the responses of neurons, microglia, and astrocytes to this type of stimulation. This included morphological assessments of the cells, viability, as well as shape and fiber outgrowth relative to the orientation of the direct current electric field. We also undertook enzyme-linked immunosorbent assays and western immunoblotting to identify which molecular pathways were affected by direct current electric fields. In response to direct current electric field, neurons developed an elongated cell body shape with neurite outgrowth that was associated with a significant increase in growth associated protein-43. Fetal midbrain dopaminergic explants grown in a collagen gel matrix also showed a reorientation of their neurites towards the cathode. BV2 microglial cells adopted distinct morphological changes with an increase in cyclooxygenase-2 expression, but these were dependent on whether they had already been activated with lipopolysaccharide. Finally, astrocytes displayed elongated cell bodies with cellular filopodia that were oriented perpendicularly to the direct current electric field. We show that cells of the central nervous system can respond to direct current electric fields both in terms of their morphological shape and molecular expression of certain proteins, and this in turn can help us to begin understand the mechanisms underlying the clinical benefits of direct current electric field. © The Author 2015. Published by Oxford University Press on behalf of CINP.

  12. Letter Report on 500 nA Pulsed Current from Field Ionization Source

    International Nuclear Information System (INIS)

    Ellsworth, Jennifer L.

    2013-01-01

    We recently produced a milestone 500 nA of pulsed current using 40 Ir field ionizer electrodes in our ion source. In conclusion, we have produced the milestone pulsed current of 500 nA using 40 electrochemically etched iridium tips in a field ionization source. The pulsed current output is repeatable and scales as expected with gas fill pressure and bias voltage. We expect these current will be sufficient to produce neutral yields of 1 · 10 7 DT n/s.

  13. Resonant geomagnetic field oscillations and Birkeland currents in the morning sector

    International Nuclear Information System (INIS)

    Potemra, T.A.; Zanetti, L.J.; Bythrow, P.F.; Erlandson, R.E.; Lundin, R.; Marklund, G.T.; Block, L.P.; Lindqvist, P.A.

    1988-01-01

    Magnetic field, electric field, and particle measurements acquired by the Viking satellite and magnetic field measurements acquired by the Active Magnetosphere Particle Tracer Explorers (AMPTE) CCE satellite have been used to study the relationship between large-scale Birkeland currents and resonant oscillations in the Earth's magnetic field. Region 1, region 2, and northward B Z (NBZ) Birkeland currents were identified with the data acquired by the Viking magnetic field instrument. Magnetic field oscillations, present in each of the 10 consecutive Viking passes studied here, have periods between 1 min. and 6 min. and amplitudes from 5 nT to 60 nT. These oscillations extend from lower L shells where they correlate with the CCCE observations up to at least the interface between the region 1 and region 2 Birkeland current system. The Viking particle observations confirm that the region 1/region 2 interface maps closely to the interface between the low-latitude boundary layer (LLBL) and the central plasma sheet (CPS). Electric and magnetic field variations are closely correlated in the region 1 Birkeland current. In the region 2 system of Birkeland currents, the northward electric and eastward magnetic field components show the same resonance oscillations with the electric field variations leading the magnetic field by approximately 90 degree. There is evidence that the amplitudes of the oscillations observed by Viking are correlated with interplanetary magnetic field (IMF) cone angle. In one case, the energy-time dispersion signature of temporal magnetosheath plasma injection into the low-latitude boundary layer was associated with the resonant oscillations. These relationships and the presence of the resonant oscillations on field lines up to the region 1/region 2 (LLBL/CPS) interface lead us to conclude that there are several features in the solar wind and the direction of the IMF that can initiate magnetospheric pulsations

  14. Control of tokamak plasma current and equilibrium with hybrid poloidal field coils

    International Nuclear Information System (INIS)

    Shimada, Ryuichi

    1982-01-01

    A control method with hybrid poloidal field system is considered, which comprehensively implements the control of plasma equilibrium and plasma current, those have been treated independently in Tokamak divices. Tokamak equilibrium requires the condition that the magnetic flux function value on plasma surface must be constant. From this, the current to be supplied to each coil is determined. Therefore, each coil current is the resultant of the component related to plasma current excitation and the component required for holding equilibrium. Here, it is intended to show a method by which the current to be supplied to each coil can easily be calculated by the introduction of hybrid control matrix. The text first considers the equilibrium of axi-symmetrical plasma and the equilibrium magnetic field outside plasma, next describes the determination of current using the above hybrid control matrix, and indicates an example of controlling Tokamak plasma current and equilibrium by the hybrid poloidal field coils. It also shows that the excitation of plasma current and the maintenance of plasma equilibrium can basically be available with a single power supply by the appropriate selection of the number of turns of each coil. These considerations determine the basic system configuration as well as decrease the installed capacity of power source for the poloidal field of a Tokamak fusion reactor. Finally, the actual configuration of the power source for hybrid poloidal field coils is shown for the above system. (Wakatsuki, Y.)

  15. Current limitation and formation of plasma double layers in a non-uniform magnetic field

    International Nuclear Information System (INIS)

    Plamondon, R.; Teichmann, J.; Torven, S.

    1986-07-01

    Formation of strong double layers has been observed experimentally in a magnetised plasma column maintained by a plasma source. The magnetic field is approximately axially homogenous except in a region at the anode where the electric current flows into a magnetic mirror. The double layer has a stationary position only in the region of non-uniform magnetic field or at the aperture separating the source and the plasma column. It is characterized by a negative differential resistance in the current-voltage characteristic of the device. The parameter space,where the double layer exists, has been studied as well as the corresponding potential profiles and fluctuation spectra. The electric current and the axial electric field are oppositely directed between the plasma source and a potential minimum which is formed in the region of inhomogeneous magnetic field. Electron reflection by the resulting potential barrier is found to be an important current limitation mechanism. (authors)

  16. Self-consistent neutral point current and fields from single particle dynamics

    International Nuclear Information System (INIS)

    Martin, R.F. Jr.

    1988-01-01

    In order to begin to build a global model of the magnetotail-auroral region interaction, it is of interest to understand the role of neutral points as potential centers of particle energization in the tail. In this paper, the single particle current is calculated near a magnetic neutral point with magnetotail properties. This is balanced with the Ampere's law current producing the magnetic field to obtain the self-consistent electric field for the problem. Also calculated is the current-electric field relationship and, in the regime where this relation is linear, an effective conductivity. Results for these macroscopic quantities are surprisingly similar to the values calculated for a constant normal field current sheet geometry. Application to magnetotail modeling is discussed. 11 references

  17. SSWL and BWL: finite element models of compressed magnetic field current generators

    Energy Technology Data Exchange (ETDEWEB)

    Tucker, T.J.; Leeman, J.E.

    1976-01-01

    Documentation is presented for two new computer codes modeling the behavior of compressed magnetic field current generators. Code output results for the typical generator configurations are presented and compared to experimental results. (auth)

  18. Spin current pumped by a rotating magnetic field in zigzag graphene nanoribbons

    International Nuclear Information System (INIS)

    Wang, J; Chan, K S

    2010-01-01

    We study electron spin resonance in zigzag graphene nanoribbons by applying a rotating magnetic field on the system without any bias. By using the nonequilibrium Green's function technique, the spin-resolved pumped current is explicitly derived in a rotating reference frame. The pumped spin current density increases with the system size and the intensity of the transverse rotating magnetic field. For graphene nanoribbons with an even number of zigzag chains, there is a nonzero pumped charge current in addition to the pumped spin current owing to the broken spatial inversion symmetry of the system, but its magnitude is much smaller than the spin current. The short-ranged static disorder from either impurities or defects in the ribbon can depress the spin current greatly due to the localization effect, whereas the long-ranged disorder from charge impurities can avoid inter-valley scattering so that the spin current can survive in the strong disorder for the single-energy mode.

  19. An Investigation of Hall Currents Associated with Tripolar Magnetic Fields During Magnetospheric Kelvin Helmholtz Waves

    Science.gov (United States)

    Sturner, A. P.; Eriksson, S.; Newman, D. L.; Lapenta, G.; Gershman, D. J.; Plaschke, F.; Ergun, R.; Wilder, F. D.; Torbert, R. B.; Giles, B. L.; Strangeway, R. J.; Russell, C. T.; Burch, J. L.

    2016-12-01

    Kinetic simulations and observations of magnetic reconnection suggest the Hall term of Ohm's Law is necessary for understanding fast reconnection in the Earth's magnetosphere. During high (>1) guide field plasma conditions in the solar wind and in Earth's magnetopause, tripolar variations in the guide magnetic field are often observed during current sheet crossings, and have been linked to reconnection Hall magnetic fields. Two proposed mechanisms for these tripolar variations are the presence of multiple nearby X-lines and magnetic island coalescence. We present results of an investigation into the structure of the electron currents supporting tripolar guide magnetic field variations during Kelvin-Helmholtz wave current sheet crossings using the Magnetosphere Multiscale (MMS) Mission, and compare with bipolar magnetic field structures and with kinetic simulations to understand how these tripolar structures may be used as tracers for magnetic islands.

  20. Prospects for Off-axis Current Drive via High Field Side Lower Hybrid Current Drive in DIII-D

    Science.gov (United States)

    Wukitch, S. J.; Shiraiwa, S.; Wallace, G. M.; Bonoli, P. T.; Holcomb, C.; Park, J. M.; Pinsker, R. I.

    2017-10-01

    An outstanding challenge for an economical, steady state tokamak is efficient off-axis current drive scalable to reactors. Previous studies have focused on high field side (HFS) launch of lower hybrid waves for current drive (LHCD) in double null configurations in reactor grade plasmas. The goal of this work is to find a HFS LHCD scenario for DIII-D that balances coupling, power penetration and damping. The higher magnetic field on the HFS improves wave accessibility, which allows for lower n||waves to be launched. These waves penetrate farther into the plasma core before damping at higher Te yielding a higher current drive efficiency. Utilizing advanced ray tracing and Fokker Planck simulation tools (GENRAY+CQL3D), wave penetration, absorption and drive current profiles in high performance DIII-D H-Mode plasmas were investigated. We found LH scenarios with single pass absorption, excellent wave penetration to r/a 0.6-0.8, FWHM r/a=0.2 and driven current up to 0.37 MA/MW coupled. These simulations indicate that HFS LHCD has potential to achieve efficient off-axis current drive in DIII-D and the latest results will be presented. Work supported by U.S. Dept. of Energy, Office of Science, Office of Fusion Energy Sciences, using User Facility DIII-D, under Award No. DE-FC02-04ER54698 and Contract No. DE-FC02-01ER54648 under Scientific Discovery through Advanced Computing Initiative.

  1. Coupling between eddy current and deflection in cantilevered beams in magnetic fields

    International Nuclear Information System (INIS)

    Hua, T.Q.

    1986-01-01

    Experiments were performed to investigate the coupling between eddy currents and deflection in cantilevered beams in longitudinal and transverse magnetic fields. This coupling effect reduces the current, deflection, and material stress to levels far less severe than would be predicted if coupling is disregarded. The experiments were conducted using the FELIX (Fusion ELectromagnetic Induction experiment) facility at the Argonne National Laboratory. The beams, which provide a simple model for the limiter blades in a tokamak fusion reactor, are subjected to crossed time-varying and constant magnetic fields. The time-varying field simulates the decaying field during a plasma disruption and the constant field models the toroidal field. Several test pieces are employed to allow variations in thicknesses and mechanical and electrical properties. Various magnetic field levels and decay time constants of time-varying are used to study the extent of the coupling from weak to strong coupling. The ratios of constant field to time-varying field are kept in the range from 10:1 to 20:1 as would be appropriate to tokamak limiters. Major parameters measured as functions of time are beam deflection, measured with an electro-optical device; total circulating current, measured with a Rogowski coil; strain recorded by strain gauges; and magnetic fields measured with Hall probes

  2. NUMERICAL RESEARCH TECHNIQUES OF MAGNETIC FIELDS GENERATED BY INDUCTION CURRENTS IN A MASSIVE CONDUCTOR

    OpenAIRE

    Tchernykh A. G.

    2015-01-01

    We consider the technology of application of numerical methods in the educational process in physics on the example of a study of the magnetic field induced by induction currents in a cylindrical conductor in a quasi-stationary magnetic field. Here is given the numerical calculation of the real and imaginary parts of the Bessel functions of complex argument. The listing of the program of drawing the graphs of the radial dependence of the amplitude and phase shift of the inductive currents fie...

  3. External field induced switching of tunneling current in the coupled quantum dots

    OpenAIRE

    Mantsevich, V. N.; Maslova, N. S.; Arseyev, P. I.

    2014-01-01

    We investigated the tunneling current peculiarities in the system of two coupled by means of the external field quantum dots (QDs) weakly connected to the electrodes in the presence of Coulomb correlations. It was found that tuning of the external field frequency induces fast multiple tunneling current switching and leads to the negative tunneling conductivity. Special role of multi-electrons states was demonstrated. Moreover we revealed conditions for bistable behavior of the tunneling curre...

  4. System and method for magnetic current density imaging at ultra low magnetic fields

    Science.gov (United States)

    Espy, Michelle A.; George, John Stevens; Kraus, Robert Henry; Magnelind, Per; Matlashov, Andrei Nikolaevich; Tucker, Don; Turovets, Sergei; Volegov, Petr Lvovich

    2016-02-09

    Preferred systems can include an electrical impedance tomography apparatus electrically connectable to an object; an ultra low field magnetic resonance imaging apparatus including a plurality of field directions and disposable about the object; a controller connected to the ultra low field magnetic resonance imaging apparatus and configured to implement a sequencing of one or more ultra low magnetic fields substantially along one or more of the plurality of field directions; and a display connected to the controller, and wherein the controller is further configured to reconstruct a displayable image of an electrical current density in the object. Preferred methods, apparatuses, and computer program products are also disclosed.

  5. The current algebra on the circle as a germ of local field theories

    International Nuclear Information System (INIS)

    Buchholz, D.; Mack, G.; Todorov, I.; Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika)

    1988-01-01

    Methods of algebraic quantum field theory are used to classify all field- and observable algebras, whose common germ is the U(1)-current algebra. An elementary way is described to compute characters of such algebras. It exploits the Kubo-Martin-Schwinger condition for Gibbs states. (orig.)

  6. On the origin of field-aligned beams at the quasi-perpendicular bow shock: multi-spacecraft observations by Cluster

    Directory of Open Access Journals (Sweden)

    H. Kucharek

    2004-07-01

    Full Text Available Two distinct populations of reflected and accelerated ions are known to originate from quasi-perpendicular shocks, gyrating ions and reflected ion beams. Recent observations under such bow shock conditions with Cluster have shown strong evidence that both particle distributions appear to emerge from the same reflection process. In this paper the basic production mechanism of field-aligned beams has been investigated by using CLUSTER multi-spacecraft measurements. We have analyzed several quasi-perpendicular shocks with the Cluster Ion Spectrometry experiment (CIS and followed the spatial and temporal evolution of the reflected and transmitted ion populations across the shock. These observations show that the field-aligned beams most likely result from effective scattering in pitch angle during reflection in the shock ramp. Investigating a low Mach number shock, leakage of a fraction of the thermalized ion distribution in the downstream region does not appear to be the source as the volume in phase space occupied by beam ions is empty downstream of the shock ramp.

  7. In-situ electric field and current density in Japanese male and female models for uniform magnetic field exposures

    International Nuclear Information System (INIS)

    Hirata, A.; Wake, K.; Watanabe, S.; Taki, M.

    2009-01-01

    The present study quantified the in situ electric field and induced current density in anatomically based numeric Japanese male and female models for exposure to extremely low-frequency magnetic fields. A quasi-static FDTD method was applied to analyse this problem. The computational results obtained herein reveal that the 99. percentile value of the in situ electric field in the nerve tissue and the current density averaged over an area of 1 cm 2 of the nerve tissue (excluding non-nerve tissues in the averaging region) in the female models were less than 35 and 25%, respectively. These induced quantities in the Japanese models were smaller than those for European models reported in a previous study, which is mainly due to the difference in cross-sectional area of the body. (authors)

  8. Beyond Alignment

    DEFF Research Database (Denmark)

    Beyond Alignment: Applying Systems Thinking to Architecting Enterprises is a comprehensive reader about how enterprises can apply systems thinking in their enterprise architecture practice, for business transformation and for strategic execution. The book's contributors find that systems thinking...

  9. Sodium current inhibition by nanosecond pulsed electric field (nsPEF)--fact or artifact?

    NARCIS (Netherlands)

    Verkerk, Arie O.; van Ginneken, Antoni C. G.; Wilders, Ronald

    2013-01-01

    In two recent publications in Bioelectromagnetics it has been demonstrated that the voltage-gated sodium current (I(Na)) is inhibited in response to a nanosecond pulsed electric field (nsPEF). At the same time, there was an increase in a non-inactivating "leak" current (I(leak)), which was

  10. Anomalous cross-field current and fluctuating equilibrium of magnetized plasmas

    DEFF Research Database (Denmark)

    Rypdal, K.; Garcia, O.E.; Paulsen, J.V.

    1997-01-01

    It is shown by simple physical arguments and fluid simulations that electrostatic flute-mode fluctuations can sustain a substantial cross-field current in addition to mass and energy transport. The simulations show that this current determines essential features of the fluctuating plasma...

  11. Current drive by neutral beams, rotating magnetic fields and helicity injection in compact toroids

    International Nuclear Information System (INIS)

    Farengo, R.; Arista, N.R.; Lifschitz, A.F.; Clemente, R.A.

    2003-01-01

    The use of neutral beams (NB) for current drive and heating in spheromaks, the relaxed states of flux core spheromaks (FCS) sustained by helicity injection and the effect of ion dynamics on rotating magnetic field (RMF) current drive in spherical tokamaks (ST) are studied. (author)

  12. Quantum rings in magnetic fields and spin current generation.

    Science.gov (United States)

    Cini, Michele; Bellucci, Stefano

    2014-04-09

    We propose three different mechanisms for pumping spin-polarized currents in a ballistic circuit using a time-dependent magnetic field acting on an asymmetrically connected quantum ring at half filling. The first mechanism works thanks to a rotating magnetic field and produces an alternating current with a partial spin polarization. The second mechanism works by rotating the ring in a constant field; like the former case, it produces an alternating charge current, but the spin current is dc. Both methods do not require a spin-orbit interaction to achieve the polarized current, but the rotating ring could be used to measure the spin-orbit interaction in the ring using characteristic oscillations. On the other hand, the last mechanism that we propose depends on the spin-orbit interaction in an essential way, and requires a time-dependent magnetic field in the plane of the ring. This arrangement can be designed to pump a purely spin current. The absence of a charge current is demonstrated analytically. Moreover, a simple formula for the current is derived and compared with the numerical results.

  13. Eddy current heating of irregularly shaped plates by slow ramped fields

    International Nuclear Information System (INIS)

    Dresner, L.

    1979-01-01

    Theorems are presented for estimating eddy current heating of irregularly shaped plates by a perpendicular ramped field. The theorems, which are derived from two complementary variational principles, give upper and lower bounds to the eddy current heating. Illustrative results are given for rectangles, isosceles triangles, sectors of circular annuli, rhombuses, and L-shaped plates. A comparison is made with earlier work

  14. Flavor-singlet axial-vector current in quark model within background field

    International Nuclear Information System (INIS)

    Chen Kun; Yan Mulin

    1993-01-01

    The flavor-singlet axial-vector current is calculated in a quark model within pseudoscalar background-field through the Seeley-DeWitt coefficients. This current is responsible for the quark spin content of proton and is of O(1) in the large-N e expansion

  15. Space-charge-limited currents for cathodes with electric field enhanced geometry

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Dingguo, E-mail: laidingguo@nint.ac.cn; Qiu, Mengtong; Xu, Qifu [State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi' an 701124 (China); Huang, Zhongliang [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

    2016-08-15

    This paper presents the approximate analytic solutions of current density for annulus and circle cathodes. The current densities of annulus and circle cathodes are derived approximately from first principles, which are in agreement with simulation results. The large scaling laws can predict current densities of high current vacuum diodes including annulus and circle cathodes in practical applications. In order to discuss the relationship between current density and electric field on cathode surface, the existing analytical solutions of currents for concentric cylinder and sphere diodes are fitted from existing solutions relating with electric field enhancement factors. It is found that the space-charge-limited current density for the cathode with electric-field enhanced geometry can be written in a general form of J = g(β{sub E}){sup 2}J{sub 0}, where J{sub 0} is the classical (1D) Child-Langmuir current density, β{sub E} is the electric field enhancement factor, and g is the geometrical correction factor depending on the cathode geometry.

  16. Remote sensing of local structure of the quasi-perpendicular Earth's bow shock by using field-aligned beams

    Directory of Open Access Journals (Sweden)

    B. Miao

    2009-03-01

    Full Text Available Field-aligned ion beams (FABs originate at the quasi-perpendicular Earth's bow shock and constitute an important ion population in the foreshock region. The bulk velocity of these FABs depends significantly on the shock normal angle, which is the angle between shock normal and upstream interplanetary magnetic field (IMF. This dependency may therefore be taken as an indicator of the local structure of the shock. Applying the direct reflection model to Cluster measurements, we have developed a method that uses proton FABs in the foreshock region for remote sensing of the local shock structure. The comparison of the model results with the multi-spacecraft observations of FAB events shows very good agreement in terms of wave amplitude and frequency of surface waves at the shock front.

  17. Circulating persistent current and induced magnetic field in a fractal network

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Srilekha [Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, Kolkata 700 064 (India); Maiti, Santanu K., E-mail: santanu.maiti@isical.ac.in [Physics and Applied Mathematics Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700 108 (India); Karmakar, S.N. [Condensed Matter Physics Division, Saha Institute of Nuclear Physics, Sector-I, Block-AF, Bidhannagar, Kolkata 700 064 (India)

    2016-04-29

    We present the overall conductance as well as the circulating currents in individual loops of a Sierpinski gasket (SPG) as we apply bias voltage via the side attached electrodes. SPG being a self-similar structure, its manifestation on loop currents and magnetic fields is examined in various generations of this fractal and it has been observed that for a given configuration of the electrodes, the physical quantities exhibit certain regularity as we go from one generation to another. Also a notable feature is the introduction of anisotropy in hopping causes an increase in magnitude of overall transport current. These features are a subject of interest in this article. - Highlights: • Voltage driven circular current is analyzed in a fractal network. • Current induced magnetic field is strong enough to flip a spin. • Anisotropy in hopping enhances overall transport current.

  18. Alignment of CEBAF cryomodules

    International Nuclear Information System (INIS)

    Schneider, W.J.; Bisognano, J.J.; Fischer, J.

    1993-06-01

    CEBAF, the Continuous Electron Beam Accelerator Facility, when completed, will house a 4 GeV recirculating accelerator. Each of the accelerator's two linacs contains 160 superconducting radio frequency (SRF) 1497 MHz niobium cavities in 20 cryomodules. Alignments of the cavities within the cryomodule with respect to beam axis is critical to achieving the optimum accelerator performance. This paper discusses the rationale for the current specification on cavity mechanical alignment: 2 mrad (rms) applied to the 0.5 m active length cavities. We describe the tooling that was developed to achieve the tolerance at the time of cavity pair assembly, to preserve and integrate alignment during cryomodule assembly, and to translate alignment to appropriate installation in the beam line

  19. Biaxial magnetic grain alignment

    International Nuclear Information System (INIS)

    Staines, M.; Genoud, J.-Y.; Mawdsley, A.; Manojlovic, V.

    2000-01-01

    Full text: We describe a dynamic magnetic grain alignment technique which can be used to produce YBCO thick films with a high degree of biaxial texture. The technique is, however, generally applicable to preparing ceramics or composite materials from granular materials with orthorhombic or lower crystal symmetry and is therefore not restricted to superconducting applications. Because magnetic alignment is a bulk effect, textured substrates are not required, unlike epitaxial coated tape processes such as RABiTS. We have used the technique to produce thick films of Y-247 on untextured silver substrates. After processing to Y-123 the films show a clear enhancement of critical current density relative to identically prepared untextured or uniaxially textured samples. We describe procedures for preparing materials using magnetic biaxial grain alignment with the emphasis on alignment in epoxy, which can give extremely high texture. X-ray rocking curves with FWHM of as little as 1-2 degrees have been measured

  20. Investigation of defect-induced abnormal body current in fin field-effect-transistors

    International Nuclear Information System (INIS)

    Liu, Kuan-Ju; Tsai, Jyun-Yu; Lu, Ying-Hsin; Liu, Xi-Wen; Chang, Ting-Chang; Chen, Ching-En; Yang, Ren-Ya; Cheng, Osbert; Huang, Cheng-Tung

    2015-01-01

    This letter investigates the mechanism of abnormal body current at the linear region in n-channel high-k/metal gate stack fin field effect transistors. Unlike body current, which is generated by impact ionization at high drain voltages, abnormal body current was found to increase with decreasing drain voltages. Notably, the unusual body leakage only occurs in three-dimensional structure devices. Based on measurements under different operation conditions, the abnormal body current can be attributed to fin surface defect-induced leakage current, and the mechanism is electron tunneling to the fin via the defects, resulting in holes left at the body terminal

  1. Current sustaining by RF travelling field in a collisional toroidal plasma

    International Nuclear Information System (INIS)

    Fukuda, Masaji; Matsuura, Kiyokata.

    1977-06-01

    The relation between the current generation by RF travelling field and the accompanied power absorption is studied in a collisional toroidal plasma, parameters being phase velocity and filling gas pressure or electron collision frequency. It is observed at a low magnetic field that the current is proportional to the plasma conductivity and an effective electromotive force, which is a new concept introduced on the basis of fluid model; the electromotive force is proportional to the absorbed RF power and inversely proportional to the plasma density and the phase velocity of the travelling field. (auth.)

  2. Hysteresis of critical currents of superconducting bridges in low perpendicular magnetic fields

    International Nuclear Information System (INIS)

    Aomine, T.; Tanaka, E.; Yamasaki, S.; Tani, K.; Yonekura, A.

    1989-01-01

    Hysteresis of critical currents I c of superconducting bridges with In, Nb, and NbN has been studied in low perpendicular magnetic fields. Influences of bridge geometry, small field sweep, trapped flux, and bombardment of argon ions on the hysteresis were made clear. The experimental results suggest that the edge pinning and trapped flux in the bank of bridges are associated with the hysteresis. The peak value of I c of NbN bridges, as well as granular Al and In bridges reported before, in decreasing fields agrees with the calculated pair-breaking current. The origin of the hysteresis is discussed

  3. Current sustaining by RF travelling field in a collisional toroidal plasma

    International Nuclear Information System (INIS)

    Fukuda, Masaji; Matsuura, Kiyokata

    1978-01-01

    The relation between the current generated by RF travelling field and the absorbed power is studied in a collisional toroidal plasma, parameters being phase velocity and filling gap pressure or electron collision frequency. It is observed at a low magnetic field that the current is proportional to the plasma conductivity and an effective electromotive force, which is a new concept introduced on the basis of fluid model; the electromotive force is proportional to the absorbed RF power and inversely proportional to the plasma density and the phase velocity of the travelling field. (author)

  4. Spin currents from Helium in intense-field photo-ionization

    International Nuclear Information System (INIS)

    Bhattacharyya, S; Mukherjee, Mahua; Chakrabarti, J; Faisal, F H M

    2007-01-01

    Spin dynamics is studied by computing spin-dependent ionization current of He in intense laser field in relativistic field theoretic method. Spin-flip and spin-asymmetry in current generation is obtained with circularly polarized light. The spin-flip is a dynamical effect of intense laser field on an ionized spinning electron. Transformation properties of the up and down spin ionization amplitudes show that the sign of spin can be controlled by a change of helicity of the laser photons from outside

  5. Electric field effect on the critical current of SNS-contact

    International Nuclear Information System (INIS)

    Rakhmanov, A.L.; Rozhkov, A.V.

    1995-01-01

    Electric field effect on the SNS-contact critical current is investigated in the Ginzburg-Landau theory approximation. It is shown that the electric field may cause a notable increase of the contact critical current especially if the sample temperature is close to the temperature of a superconducting transition of T sc normal layer. Electric field effect is increased with the reduction of film thickness, but it can strong enough for thick films as well at temperature close to T sc . 11 refs.; 4 figs

  6. Research and development of an aimed magnetic lead current density-magnetic field diagnostic. Final report

    International Nuclear Information System (INIS)

    1985-01-01

    A diagnostics survey was made to provide a clear definition of advanced diagnostic needs and the limitations of current approaches in addressing those needs. Special attention was given to the adequacy with which current diagnostics are interfaced to signal processing/data acquisition devices and systems. Critical evaluations of selected alternative diagnostic techniques for future R and D activities are presented. The conceptual basis of the Aimed Magnetic Lead Gradiometric system as a current density/magnetic field diagnostic is established

  7. High magnetic field science and its application in the United States current status and future directions

    CERN Document Server

    National Research Council of the National Academies

    2013-01-01

    The Committee to Assess the Current Status and Future Direction of High Magnetic Field Science in the United States was convened by the National Research Council in response to a request by the National Science Foundation. This report answers three questions: (1) What is the current state of high-field magnet science, engineering, and technology in the United States, and are there any conspicuous needs to be addressed? (2) What are the current science drivers and which scientific opportunities and challenges can be anticipated over the next ten years? (3) What are the principal existing and planned high magnetic field facilities outside of the United States, what roles have U.S. high field magnet development efforts played in developing those facilities, and what potentials exist for further international collaboration in this area? A magnetic field is produced by an electrical current in a metal coil. This current exerts an expansive force on the coil, and a magnetic field is "high" if it challenges the str...

  8. Alpha effect of Alfven waves and current drive in reversed field pinches

    International Nuclear Information System (INIS)

    Litwin, C.; Prager, S.C.

    1997-10-01

    Circularly polarized Alfven waves give rise to an α-dynamo effect that can be exploited to drive parallel current. In a open-quotes laminarclose quotes magnetic the effect is weak and does not give rise to significant currents for realistic parameters (e.g., in tokamaks). However, in reversed field pinches (RFPs) in which magnetic field in the plasma core is stochastic, a significant enhancement of the α-effect occurs. Estimates of this effect show that it may be a realistic method of current generation in the present-day RFP experiments and possibly also in future RFP-based fusion reactors

  9. Measurement of weak magnetic field of corrosion current of isolated corrosion center

    Directory of Open Access Journals (Sweden)

    I. V. Bardin

    2015-01-01

    Full Text Available A very small magnetic field of corrosion current, of the order of 10−4 Oe, generated by isolated zinc inclusion in a copper platelet placed in electrolyte has been measured for the first time with a highly sensitive giant magneto-impedance magnetometer. The total corrosion current of the inclusion is estimated comparing the measured magnetic field distribution with corresponding theoretical calculation. The estimated value of the total corrosion current turns out to be in reasonable agreement with that one obtained in the standard gravimetric measurement.

  10. Regulation of adipose-tissue-derived stromal cell orientation and motility in 2D- and 3D-cultures by direct-current electrical field.

    Science.gov (United States)

    Yang, Gang; Long, Haiyan; Ren, Xiaomei; Ma, Kunlong; Xiao, Zhenghua; Wang, Ying; Guo, Yingqiang

    2017-02-01

    Cell alignment and motility play a critical role in a variety of cell behaviors, including cytoskeleton reorganization, membrane-protein relocation, nuclear gene expression, and extracellular matrix remodeling. Direct current electric field (EF) in vitro can direct many types of cells to align vertically to EF vector. In this work, we investigated the effects of EF stimulation on rat adipose-tissue-derived stromal cells (ADSCs) in 2D-culture on plastic culture dishes and in 3D-culture on various scaffold materials, including collagen hydrogels, chitosan hydrogels and poly(L-lactic acid)/gelatin electrospinning fibers. Rat ADSCs were exposed to various physiological-strength EFs in a homemade EF-bioreactor. Changes of morphology and movements of cells affected by applied EFs were evaluated by time-lapse microphotography, and cell survival rates and intracellular calcium oscillations were also detected. Results showed that EF facilitated ADSC morphological changes, under 6 V/cm EF strength, and that ADSCs in 2D-culture aligned vertically to EF vector and kept a good cell survival rate. In 3D-culture, cell galvanotaxis responses were subject to the synergistic effect of applied EF and scaffold materials. Fast cell movement and intracellular calcium activities were observed in the cells of 3D-culture. We believe our research will provide some experimental references for the future study in cell galvanotaxis behaviors. © 2017 Japanese Society of Developmental Biologists.

  11. Pulsed transport critical currents of Bi2212 tapes in pulsed magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rogacki, K [Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw (Poland); Gilewski, A; Klamut, J [International Laboratory of High Magnetic Fields and Low Temperatures, Polish Academy of Sciences, Wroclaw (Poland); Newson, M; Jones, H [Clarendon Laboratory, University of Oxford, Oxford (United Kingdom); Glowacki, B A [IRC in Superconductivity and Department of Materials Science, University of Cambridge, Cambridge (United Kingdom)

    2002-07-01

    If high-T{sub C} superconductors are ever to be used in high-field applications, it is vital that the critical surfaces can be mapped under high-field conditions. However, the latest superconductors have high currents even at fields over 20 T, making accurate measurements very difficult due to the thermal and mechanical problems. In this paper, we compare measurements on BSCCO-2212 tape using a number of different methods, particularly an innovative pulsed transport current and pulsed field mode. We show how the analysis of the voltage signal from BSCCO-2212 tape in pulsed conditions may be used to extract the critical current in quasi-stationary conditions. The effect of a metallic substrate on the results is also briefly discussed. (author)

  12. Current densities in a pregnant woman model induced by simultaneous ELF electric and magnetic field exposure

    International Nuclear Information System (INIS)

    Cech, R; Leitgeb, N; Pediaditis, M

    2008-01-01

    The pregnant woman model SILVY was studied to ascertain to what extent the electric current densities induced by 50 Hz homogeneous electric and magnetic fields increase in the case of simultaneous exposure. By vectorial addition of the electric current densities, it could be shown that under worst case conditions the basic restrictions recommended by ICNIRP (International Commission on Non-Ionizing Radiation Protection) guidelines are exceeded within the central nervous system (CNS) of the mother, whereas in sole field exposure they are not. However, within the foetus the induced current densities do not comply with basic restrictions, either from single reference-level electric fields or from simultaneous exposure to electric and magnetic fields. Basic limits were considerably exceeded

  13. Method of correcting eddy current magnetic fields in particle accelerator vacuum chambers

    Science.gov (United States)

    Danby, Gordon T.; Jackson, John W.

    1991-01-01

    A method for correcting magnetic field aberrations produced by eddy currents induced in a particle accelerator vacuum chamber housing is provided wherein correction windings are attached to selected positions on the housing and the windings are energized by transformer action from secondary coils, which coils are inductively coupled to the poles of electro-magnets that are powered to confine the charged particle beam within a desired orbit as the charged particles are accelerated through the vacuum chamber by a particle-driving rf field. The power inductively coupled to the secondary coils varies as a function of variations in the power supplied by the particle-accelerating rf field to a beam of particles accelerated through the vacuum chamber, so the current in the energized correction coils is effective to cancel eddy current flux fields that would otherwise be induced in the vacuum chamber by power variations in the particle beam.

  14. Transition from Fowler-Nordheim field emission to space charge limited current density

    International Nuclear Information System (INIS)

    Feng, Y.; Verboncoeur, J. P.

    2006-01-01

    The Fowler-Nordheim law gives the current density extracted from a surface under strong fields, by treating the emission of electrons from a metal-vacuum interface in the presence of an electric field normal to the surface as a quantum mechanical tunneling process. Child's law predicts the maximum transmitted current density by considering the space charge effect. When the electric field becomes high enough, the emitted current density will be limited by Child's law. This work analyzes the transition of the transmitted current density from the Fowler-Nordheim law to Child's law space charge limit using a one-dimensional particle-in-cell code. Also studied is the response of the emission model to strong electric fields near the transition point. We find the transition without geometrical effort is smooth and much slower than reported previously [J. P. Barbour, W. W. Dolan, J. K. Trolan, E. E. Martin, and W. P. Dyke, Phys. Rev. 92, 45 (1953)]. We analyze the effects of geometric field enhancement and work function on the transition. Using our previous model for effective field enhancement [Y. Feng and J. P. Verboncoeur, Phys. Plasmas 12, 103301 (2005)], we find the geometric effect dominates, and enhancement β>10 can accelerate the approach to the space charge limit at practical electric field. A damped oscillation near the local plasma frequency is observed in the transient system response

  15. Mapping the earth's magnetic and gravity fields from space Current status and future prospects

    Science.gov (United States)

    Settle, M.; Taranik, J. V.

    1983-01-01

    The principal magnetic fields encountered by earth orbiting spacecraft include the main (core) field, external fields produced by electrical currents within the ionosphere and magnetosphere, and the crustal (anomaly) field generated by variations in the magnetization of the outermost portions of the earth. The first orbital field measurements which proved to be of use for global studies of crustal magnetization were obtained by a series of three satellites launched and operated from 1965 to 1971. Each of the satellites, known as a Polar Orbiting Geophysical Observatory (POGO), carried a rubidium vapor magnetometer. Attention is also given to Magsat launched in 1979, the scalar anomaly field derived from the Magsat measurements, satellite tracking studies in connection with gravity field surveys, radar altimetry, the belt of positive free air gravity anomalies situated along the edge of the Pacific Ocean basin, future technological capabilities, and information concerning data availability.

  16. Effect of accelerating field third harmonic on microtron steady-state conditions and limiting current

    International Nuclear Information System (INIS)

    Kol'tsov, A.V.; Serov, A.V.

    1992-01-01

    Setting the acceleration regime in a microtron with the resonator in which the third accelerating field harmonic is excited by accelerated clusters is considered. It is shown that excitation of the accelerating field third harmonic in the microtron resonator (E 011 mode) causes a 1.5 time increase of the range of field intensity values under which resonance particle acceleration is possible. Under moderate energies and accelerated currents (10-15 MeV, 50-80 mA) this leads to a reduction of requirements to the stability of power coming to the resonator and cathode temperature. Under accelerated currents of > 100 mA the third harmonic complicates the microtron transition to acceleration regime. The microtron transfers to stable autooscillation regime, but the current achieved in a single short pulse is increased. By varying the value of the resonator quality factor on the third harmonic one can change the current pulse duration and autooscillation period

  17. Field generated within the SSC magnets due to persistant currents in the superconductor

    International Nuclear Information System (INIS)

    Green, M.A.

    1984-01-01

    This report presents the results of a number of computer studies of the magnetic fields generated by persistent circulating currents in the superconductor of superconducting dipoles. These magnetic fields are referred to as residual fields throughout this report. Since the field generated by persistent currents have a hysteric behavior, they are analagous to the residual filed found in iron bound conventional solenoids. The residual field calculations presented in this report were done using the LBL SCMAG4 computer code. This code has not been well tested against measured data, but a comparison with measured CBA data given in this report suggests that good agreement is possible. The residual fields generated by persistent superconducting currents are rich in higher multipoles. This is of concern to the accelerator designer for SSC. This report shows the effect of various superconductor parameters and coil parameters on the magnitude and structure of the residual fields. The effect of the magnet charging history on residual fields is aldo discussed. 14 references

  18. Electrical design of a high current density air-core reversed-field pinch ''ZTP''

    International Nuclear Information System (INIS)

    Reass, W.A.; Cribble, R.F.; Melton, J.G.

    1983-01-01

    This paper describes the electrical design of a small, high current density (10 MA/m 2 ) toroidal reversed-field Z-Pinch (RFP) presently being constructed at Los Alamos. Special purpose magnetic field programs were used to calculate self and mutual inductances for the poloidal field windings. The network analysis program MINI-SCEPTRE was then used to predict plasma current, including the interaction between toroidal and poloidal field circuits, as described by the Bessel function model for RFP's. Using these programs, coil geometry was obtained for minimal field errors and the pulse power systems were optimized to minimize equilibrium control power. Results of computer modeling and implementation of the electrical circuits are presented

  19. Electrical design of a high current density air-core reversed-field pinch ZTP

    International Nuclear Information System (INIS)

    Reass, W.A.; Melton, J.G.; Gribble, R.F.

    1983-01-01

    This paper describes the electrical design of a small, high current density (10 MA/m 2 ) toroidal reversed-field Z-Pinch (RFP) presently being constructed at Los Alamos. Special purpose magnetic field programs were used to calculate self and mutual inductances for the poloidal field windings. The network analysis program MINI-SCEPTRE was then used to predict plasma current, including the interaction between toroidal and poloidal field circuits, as described by the Bessel function model for RFP's. Using these programs, coil geometry was obtained for minimal field errors and the pulse power systems were optimized to minimize equilibrium control power. Results of computer modeling and implementation of the electrical circuits are presented

  20. Fluxball magnetic field analysis using a hybrid analytical/FEM/BEM with equivalent currents

    International Nuclear Information System (INIS)

    Fernandes, João F.P.; Camilo, Fernando M.; Machado, V. Maló

    2016-01-01

    In this paper, a fluxball electric machine is analyzed concerning the magnetic flux, force and torque. A novel method is proposed based in a special hybrid FEM/BEM (Finite Element Method/Boundary Element Method) with equivalent currents by using an analytical treatment for the source field determination. The method can be applied to evaluate the magnetic field in axisymmetric problems, in the presence of several magnetic materials. Same results obtained by a commercial Finite Element Analysis tool are presented for validation purposes with the proposed method. - Highlights: • The Fluxball machine magnetic field is analyzed by a new FEM/BEM/Analytical method. • The method is adequate for axisymmetric non homogeneous magnetic field problems. • The source magnetic field is evaluated considering a non-magnetic equivalent problem. • Material magnetization vectors are accounted by using equivalent currents. • A strong reduction of the finite element domain is achieved.

  1. Distilling two-center-interference information during tunneling of aligned molecules with orthogonally polarized two-color laser fields

    Science.gov (United States)

    Gao, F.; Chen, Y. J.; Xin, G. G.; Liu, J.; Fu, L. B.

    2017-12-01

    When electrons tunnel through a barrier formed by the strong laser field and the two-center potential of a diatomic molecule, a double-slit-like interference can occur. However, this interference effect can not be probed directly right now, as it is strongly coupled with other dynamical processes during tunneling. Here, we show numerically and analytically that orthogonally polarized two-color (OTC) laser fields are capable of resolving the interference effect in tunneling, while leaving clear footprints of this effect in photoelectron momentum distributions. Moreover, this effect can be manipulated by changing the relative field strength of OTC fields.

  2. A Novel High Sensitivity Sensor for Remote Field Eddy Current Non-Destructive Testing Based on Orthogonal Magnetic Field

    Directory of Open Access Journals (Sweden)

    Xiaojie Xu

    2014-12-01

    Full Text Available Remote field eddy current is an effective non-destructive testing method for ferromagnetic tubular structures. In view of conventional sensors’ disadvantages such as low signal-to-noise ratio and poor sensitivity to axial cracks, a novel high sensitivity sensor based on orthogonal magnetic field excitation is proposed. Firstly, through a three-dimensional finite element simulation, the remote field effect under orthogonal magnetic field excitation is determined, and an appropriate configuration which can generate an orthogonal magnetic field for a tubular structure is developed. Secondly, optimized selection of key parameters such as frequency, exciting currents and shielding modes is analyzed in detail, and different types of pick-up coils, including a new self-differential mode pick-up coil, are designed and analyzed. Lastly, the proposed sensor is verified experimentally by various types of defects manufactured on a section of a ferromagnetic tube. Experimental results show that the proposed novel sensor can largely improve the sensitivity of defect detection, especially for axial crack whose depth is less than 40% wall thickness, which are very difficult to detect and identify by conventional sensors. Another noteworthy advantage of the proposed sensor is that it has almost equal sensitivity to various types of defects, when a self-differential mode pick-up coil is adopted.

  3. Magnetic field and electric currents in the vicinity of polar cusps as inferred from Polar and Cluster data

    Directory of Open Access Journals (Sweden)

    N. A. Tsyganenko

    2009-04-01

    Full Text Available A detailed statistical study of the magnetic structure of the dayside polar cusps is presented, based on multi-year sets of magnetometer data of Polar and Cluster spacecraft, taken in 1996–2006 and 2001–2007, respectively. Thanks to the dense data coverage in both Northern and Southern Hemispheres, the analysis spanned nearly the entire length of the cusps, from low altitudes to the cusp "throat" and the magnetosheath. Subsets of data falling inside the polar cusp "funnels" were selected with the help of TS05 and IGRF magnetic field models, taking into account the dipole tilt and the solar wind/IMF conditions. The selection funnels were shifted within ±10° of SM latitude around the model cusp location, and linear regression parameters were calculated for each sliding subset, further divided into 10 bins of distance in the range 2≤R≤12 RE, with the following results. (1 Diamagnetic depression, caused by the penetrated magnetosheath plasma, becomes first visible at R~4–5 RE, rapidly deepens with growing R, peaks at R~6–9 RE, and then partially subsides and widens in latitude at the cusp's outer end. (2 The depression peak is systematically shifted poleward (by ~2° of the footpoint latitude with respect to the model cusp field line, passing through the min{|B|} point at the magnetopause. (3 At all radial distances, clear and distinct peaks of the correlation between the local By and By(IMF and of the corresponding proportionality coefficient are observed. A remarkably regular variation of that coefficient with R quantitatively confirms the field-aligned geometry of the cusp currents associated with the IMF By, found in earlier observations.

  4. How can we probe the atom mass currents induced by synthetic gauge fields?

    Science.gov (United States)

    Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

    2013-05-01

    Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

  5. THE NIOBIUM-THORIUM EUTECTIC ALLOY AS A HIGH-FIELD, HIGH-CURRENT SUPERCONDUCTOR

    Energy Technology Data Exchange (ETDEWEB)

    Cline, H. E.; Rose, R. M.; Wulff, J.

    1963-03-15

    Niobium-thorium eutectic alloys having fine acicuiar microstructures were produced by fast cooling frorn a vacuum melt. Although the solidified material was normal, continuity between the superconducting niobium-rich phase, which was essentially pure niobium, was attained by plastic deformation at room temperature. The resulting wire was tested for critical current at 4.2 deg K, in transverse magnetic fields up to 82.5 kilogauss; at the highest field, critical current densities of slightly more than 10/sup 4/ amps per square centimeter were observed. The critical current density was independent of applied field from 20 kilogauss to the highest field used; the level of critical current density depended on diameter in a manner that suggested dependence on cold work. It was concluded that the cold work reduced the thickness of the needles of niobium below the superconducting penetration depth, and brought them sufficiently close together to allow the superconducting correlation to interconnect the niobium, in the manner suggested by Cooper; furthermore, the constant critical current region may possibly extend to considerably higher fields. (auth)

  6. Pulsed currents carried by whistlers. IV. Electric fields and radiation excited by an electrode

    International Nuclear Information System (INIS)

    Stenzel, R.L.; Urrutia, J.M.; Rousculp, C.L.

    1995-01-01

    Electromagnetic properties of current pulses carried by whistler wave packets are obtained from a basic laboratory experiment. While the magnetic field and current density are described in the preceding companion paper (Part III), the present analysis starts with the electric field. The inductive and space charge electric field contributions are separately calculated in Fourier space from the measured magnetic field and Ohm's law along B 0 . Inverse Fourier transformation yields the total electric field in space and time, separated into rotational and divergent contributions. The space-charge density in whistler wave packets is obtained. The cross-field tensor conductivity is determined. The frozen-in condition is nearly satisfied, E+v e xB congruent 0. The dissipation is obtained from Poynting's theorem. The waves are collisionally damped; Landau damping is negligible. A radiation resistance for the electrode is determined. Analogous to Poynting's theorem, the transport of helicity is analyzed. Current helicity is generated by a flow of helicity between pulses traveling in opposite directions which carry opposite signs of helicity. Helicity is dissipated by collisions. These observations complete a detailed description of whistler/current pulses which can occur in various laboratory and space plasmas. copyright 1995 American Institute of Physics

  7. Effect of frictional heating on radiative ferrofluid flow over a slendering stretching sheet with aligned magnetic field

    Science.gov (United States)

    Ramana Reddy, J. V.; Sugunamma, V.; Sandeep, N.

    2017-01-01

    The pivotal objective of this paper is to look into the flow of ferrofluids past a variable thickness surface with velocity slip. Magnetite (Fe3O4 nanoparticles are embedded to the regular fluid. The occurrence of frictional heating in the flow is also taken into account. So the flow equations will be coupled and nonlinear. These are remodelled into dimensionless form with the support of suitable transmutations. The solution of the transformed equations is determined with the support of an effective Runge-Kutta (RK)-based shooting technique. Ultimately, the effects of a few flow modulating quantities on fluid motion and heat transport were explored through plots which are procured using the MATLAB tool box. Owing to the engineering applications, we also calculated the friction factor and the heat transfer coefficient for the influencing parameters. The results are presented comparatively for both regular fluid (water) and water-based ferrofluid. This study enables us to deduce that inflation in the aligned angle or surface thickness reduces the fluid velocity. The radiation and dissipation parameters are capable of providing heat energy to the flow.

  8. Wireless current sensing by near field induction from a spin transfer torque nano-oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Ramaswamy, B. [Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742 (United States); Algarin, J. M.; Waks, E., E-mail: edowaks@umd.edu [Institute for Research in Electronics and Applied Physics (IREAP), University of Maryland, College Park, Maryland 20742 (United States); Weinberg, I. N. [Weinberg Medical Physics LLC, Bethesda, Maryland 20817 (United States); Chen, Y.-J.; Krivorotov, I. N. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Katine, J. A. [HGST Research Center, San Jose, California 95135 (United States); Shapiro, B. [Fischell Department of Bioengineering, University of Maryland, College Park, Maryland 20742 (United States); Institute for Systems Research (ISR), University of Maryland, College Park, Maryland 20742 (United States)

    2016-06-13

    We demonstrate that spin transfer torque nano-oscillators (STNO) can act as wireless sensors for local current. The STNO acts as a transducer that converts weak direct currents into microwave field oscillations that we detect using an inductive coil. We detect direct currents in the range of 300–700 μA and report them wirelessly to a receiving induction coil at distances exceeding 6.5 mm. This current sensor could find application in chemical and biological sensing and industrial inspection.

  9. Current-voltage characteristics of a superconducting slab under a superimposed small AC magnetic field

    International Nuclear Information System (INIS)

    Matsushita, Teruo; Yamafuji, Kaoru; Sakamoto, Nobuyoshi.

    1977-01-01

    In case of applying superconductors to electric machinery or high intensity field magnets for fusion reactors, the superconductors are generally expected to be sensible to small field fluctuation besides DC magnetic field. The behavior of superconductors in DC magnetic field superimposed with small AC magnetic field has been investigated often experimentally, and the result has been obtained that the critical current at which DC flow voltage begins to appear extremely decreased or disappeared. Some theoretical investigations have been carried out on this phenomenon so far, however, their application has been limited to the region where frequency is sufficiently low or which is close to the critical magnetic field. Purpose of this report is to deal with the phenomenon in more unified way by analyzing the behavior of magnetic flux lines in a superconductor under a superimposed small AC field using the criticalstate model including viscous force. In order to solve the fundamental equation in this report, first the solution has been obtained in the quasi-static state neglecting viscous force, then about the cases that current density J is not more than Jc and J is larger than Jc, concerning the deviation from the quasi-static limit by employing successive approximation. Current-voltage characteristics have been determined by utilizing the above results. This method seems to be most promising at present except the case of extremely high frequency. (Wakatsuki, Y.)

  10. Enhancing Photoresponsivity of Self-Aligned MoS2 Field-Effect Transistors by Piezo-Phototronic Effect from GaN Nanowires.

    Science.gov (United States)

    Liu, Xingqiang; Yang, Xiaonian; Gao, Guoyun; Yang, Zhenyu; Liu, Haitao; Li, Qiang; Lou, Zheng; Shen, Guozhen; Liao, Lei; Pan, Caofeng; Lin Wang, Zhong

    2016-08-23

    We report high-performance self-aligned MoS2 field-effect transistors (FETs) with enhanced photoresponsivity by the piezo-phototronic effect. The FETs are fabricated based on monolayer MoS2 with a piezoelectric GaN nanowire (NW) as the local gate, and a self-aligned process is employed to define the source/drain electrodes. The fabrication method allows the preservation of the intrinsic property of MoS2 and suppresses the scattering center density in the MoS2/GaN interface, which results in high electrical and photoelectric performances. MoS2 FETs with channel lengths of ∼200 nm have been fabricated with a small subthreshold slope of 64 mV/dec. The photoresponsivity is 443.3 A·W(-1), with a fast response and recovery time of ∼5 ms under 550 nm light illumination. When strain is introduced into the GaN NW, the photoresponsivity is further enhanced to 734.5 A·W(-1) and maintains consistent response and recovery time, which is comparable with that of the mechanical exfoliation of MoS2 transistors. The approach presented here opens an avenue to high-performance top-gated piezo-enhanced MoS2 photodetectors.

  11. Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

    International Nuclear Information System (INIS)

    Abraimov, D; Francis, A; Jaroszynski, J; McCallister, J; Polyanskii, A; Santos, M; Viouchkov, Y L; Ballarino, A; Bottura, L; Rossi, L; Barth, C; Senatore, C; Dietrich, R; Rutt, A; Schlenga, K; Usoskin, A; Majkic, G S; Selvamanickam, V

    2015-01-01

    A significant increase of critical current in high magnetic field, up to 31 T, was recorded in long tapes manufactured by employing a double-disorder route. In a double-disordered high-temperature superconductor (HTS), a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa 2 Cu 3 O x−δ matrix and (ii) the extrinsic disorder is introduced via embedded atoms or particles of foreign material (e.g. barium zirconate), which create a set of lattice defects. We analyzed possible technological reasons for this current gain. The properties of these tapes over a wider field-temperature range as well as field anisotropy were also studied. Record values of critical current as high as 309 A at 31 T, 500 A at 18 Tm and 1200 A at 5 T were found in 4 mm wide tape at 4.2 K and B perpendicular to tape surface. HTS layers were processed in medium-scale equipment that allows a maximum batch length of 250 m while 22 m long batches were provided for investigation. Abnormally high ratios (up to 10) of critical current density measured at 4.2 K, 19 T to critical current density measured at 77 K, self-field were observed in tapes with the highest in-field critical current. Anisotropy of the critical current as well as angular dependences of n and α values were investigated. The temperature dependence of critical current is presented for temperatures between 4.2 and 40 K. Prospects for the suppression of the dog-bone effect by Cu plating and upscale of processing chain to >500 m piece length are discussed. (paper)

  12. Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

    Science.gov (United States)

    Abraimov, D.; Ballarino, A.; Barth, C.; Bottura, L.; Dietrich, R.; Francis, A.; Jaroszynski, J.; Majkic, G. S.; McCallister, J.; Polyanskii, A.; Rossi, L.; Rutt, A.; Santos, M.; Schlenga, K.; Selvamanickam, V.; Senatore, C.; Usoskin, A.; Viouchkov, Y. L.

    2015-11-01

    A significant increase of critical current in high magnetic field, up to 31 T, was recorded in long tapes manufactured by employing a double-disorder route. In a double-disordered high-temperature superconductor (HTS), a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa2Cu3O x-δ matrix and (ii) the extrinsic disorder is introduced via embedded atoms or particles of foreign material (e.g. barium zirconate), which create a set of lattice defects. We analyzed possible technological reasons for this current gain. The properties of these tapes over a wider field-temperature range as well as field anisotropy were also studied. Record values of critical current as high as 309 A at 31 T, 500 A at 18 Tm and 1200 A at 5 T were found in 4 mm wide tape at 4.2 K and B perpendicular to tape surface. HTS layers were processed in medium-scale equipment that allows a maximum batch length of 250 m while 22 m long batches were provided for investigation. Abnormally high ratios (up to 10) of critical current density measured at 4.2 K, 19 T to critical current density measured at 77 K, self-field were observed in tapes with the highest in-field critical current. Anisotropy of the critical current as well as angular dependences of n and α values were investigated. The temperature dependence of critical current is presented for temperatures between 4.2 and 40 K. Prospects for the suppression of the dog-bone effect by Cu plating and upscale of processing chain to >500 m piece length are discussed.

  13. A simulation of a multifilamentary wire carrying a transport current in an AC applied field

    International Nuclear Information System (INIS)

    Rem, P.C.; Hartmann, R.A.; Dijkstra, D.; Van Beckum, F.P.H.; Van de Klundert, L.J.M.

    1986-01-01

    The problem of calculating the current distribution in a multi-filamentary wire subjected to a time-dependent field becomes difficult as soon as the non-linearity due to the saturation of layers of filaments can be neglected no more. Such a problem can be solved approximately if the shape of the boundaries between unsaturated regions can be prescribed on the basis of general considerations such as symmetry arguments. For cases involving both a transport current and an applied field, however, little is known about the boundaries and their time-dependence behaviour. For such cases a brute force numerical calculation may provide an answer. The results presented below were calculated for a combination of DC transport current and AC applied field

  14. Designing an optimum pulsed magnetic field by a resistance/self-inductance/capacitance discharge system and alignment of carbon nanotubes embedded in polypyrrole matrix

    Science.gov (United States)

    Kazemikia, Kaveh; Bonabi, Fahimeh; Asadpoorchallo, Ali; Shokrzadeh, Majid

    2015-02-01

    In this work, an optimized pulsed magnetic field production apparatus is designed based on a RLC (Resistance/Self-inductance/Capacitance) discharge circuit. An algorithm for designing an optimum magnetic coil is presented. The coil is designed to work at room temperature. With a minor physical reinforcement, the magnetic flux density can be set up to 12 Tesla with 2 ms duration time. In our design process, the magnitude and the length of the magnetic pulse are the desired parameters. The magnetic field magnitude in the RLC circuit is maximized on the basis of the optimal design of the coil. The variables which are used in the optimization process are wire diameter and the number of coil layers. The coil design ensures the critically damped response of the RLC circuit. The electrical, mechanical, and thermal constraints are applied to the design process. A locus of probable magnetic flux density values versus wire diameter and coil layer is provided to locate the optimum coil parameters. Another locus of magnetic flux density values versus capacitance and initial voltage of the RLC circuit is extracted to locate the optimum circuit parameters. Finally, the application of high magnetic fields on carbon nanotube-PolyPyrrole (CNT-PPy) nano-composite is presented. Scanning probe microscopy technique is used to observe the orientation of CNTs after exposure to a magnetic field. The result shows alignment of CNTs in a 10.3 Tesla, 1.5 ms magnetic pulse.

  15. Relativistic Néel-Order Fields Induced by Electrical Current in Antiferromagnets

    KAUST Repository

    Železný, J.

    2014-10-06

    We predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn2Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

  16. Calculation of an axisymmetric current coil field with the bounding contour integration method

    Energy Technology Data Exchange (ETDEWEB)

    Telegin, Alexander P.; Klevets, Nickolay I. E-mail: pmsolution@mail.ru

    2004-06-01

    Method for the economic and stable (in the sense of calculation errors) analysis of an induction of a magnetic field created with axisymmetric coils in arbitrary points of space, including points located inside a coil or on its border, is obtained. The basic idea of the method is to replace a current coil with continuous distribution of current density by magnetization distributed in the volume of the coil and creating the equivalent magnetic field. This allows to use field surface sources at calculation of the fields. Consequently, the range of integration is reduced resulting in reduction of calculation volume by an order in most cases. Besides, the calculation of improper integrals in internal points and on the border is completely excluded.

  17. Calculation of an axisymmetric current coil field with the bounding contour integration method

    International Nuclear Information System (INIS)

    Telegin, Alexander P.; Klevets, Nickolay I.

    2004-01-01

    Method for the economic and stable (in the sense of calculation errors) analysis of an induction of a magnetic field created with axisymmetric coils in arbitrary points of space, including points located inside a coil or on its border, is obtained. The basic idea of the method is to replace a current coil with continuous distribution of current density by magnetization distributed in the volume of the coil and creating the equivalent magnetic field. This allows to use field surface sources at calculation of the fields. Consequently, the range of integration is reduced resulting in reduction of calculation volume by an order in most cases. Besides, the calculation of improper integrals in internal points and on the border is completely excluded

  18. Charge and spin current oscillations in a tunnel junction induced by magnetic field pulses

    Energy Technology Data Exchange (ETDEWEB)

    Dartora, C.A., E-mail: cadartora@eletrica.ufpr.br [Electrical Engineering Department, Federal University of Parana (UFPR), C.P. 19011 Curitiba, 81.531-970 PR (Brazil); Nobrega, K.Z., E-mail: bzuza1@yahoo.com.br [Federal Institute of Education, Science and Technolgy of Maranhão (IFMA), Av. Marechal Castelo Branco, 789, São Luís, 65.076-091 MA (Brazil); Cabrera, G.G., E-mail: cabrera@ifi.unicamp.br [Instituto de Física ‘Gleb Wataghin’, Universidade Estadual de Campinas (UNICAMP), C.P. 6165, Campinas 13.083-970 SP (Brazil)

    2016-08-15

    Usually, charge and spin transport properties in tunnel junctions are studied in the DC bias regime and/or in the adiabatic regime of time-varying magnetic fields. In this letter, the temporal dynamics of charge and spin currents in a tunnel junction induced by pulsed magnetic fields is considered. At low bias voltages, energy and momentum of the conduction electrons are nearly conserved in the tunneling process, leading to the description of the junction as a spin-1/2 fermionic system coupled to time-varying magnetic fields. Under the influence of pulsed magnetic fields, charge and spin current can flow across the tunnel junction, displaying oscillatory behavior, even in the absence of DC bias voltage. A type of spin capacitance function, in close analogy to electric capacitance, is predicted.

  19. Relativistic Néel-Order Fields Induced by Electrical Current in Antiferromagnets

    KAUST Repository

    Železný , J.; Gao, H.; Vý borný , K.; Zemen, J.; Mašek, J.; Manchon, Aurelien; Wunderlich, J.; Sinova, Jairo; Jungwirth, T.

    2014-01-01

    We predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn2Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

  20. Solar causes of the excitation of earth electric currents and of geomagnetic field disturbances

    International Nuclear Information System (INIS)

    Krivsky, L.

    1977-01-01

    A survey is given of the effects of solar activity on geomagnetic and geoelectric disturbances. Indexes are given showing changes in the magnetic field, the occurrence of calm geomagnetic days related to solar activity, proton solar flares and electrical currents in the high layers of the atmosphere in the polar region, powerfull solar activity and electric currents in the polar region, the time rise of shock waves in the development of proton flares and the boundaries of sector structures of the interplanetary magnetic field and its effect on the Earth. It is stated that the geoelectric and geomagnetic fields are affected by the discrete phenomena of solar activity and by the transition of the quasimagnetic sectors of interplanetary fields. (J.P.)

  1. Field- and current-driven domain wall dynamics: An experimental picture

    International Nuclear Information System (INIS)

    Beach, G.S.D.; Knutson, C.; Tsoi, M.; Erskine, J.L.

    2007-01-01

    Field- and current-driven domain wall velocities are measured and discussed in terms of existing spin-torque models. A reversal in the roles of adiabatic and non-adiabatic spin-torque is shown to arise in those models below and above Walker breakdown. The measured dependence of velocity on current is the same in both regimes, indicating both spin-torque components have similar magnitude. However, the models on which these conclusions are based have serious quantitative shortcomings in describing the observed field-driven wall dynamics, for which they were originally developed. Hence, the applicability of simple one-dimensional models to most experimental conditions may be limited

  2. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    International Nuclear Information System (INIS)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-01-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG 1 ) and MOSFET circuits (HCMFG 2 ) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed

  3. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Science.gov (United States)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  4. Magnetic field dependence of the current flowing in the spin-coated chlorophyll thin films

    Science.gov (United States)

    Aji, J. R. P.; Kusumandari; Purnama, B.

    2018-03-01

    The magnetic dependence of the current flowing in the spin coated chlorophyll films on a patterned Cu PCB substrate has been presented. Chlorophyll was isolated from Spirulina sp and deposited by spin coated methods. The reducing of current by the change of magnetic field (magneto conductance effect) was performed by inducing the magnetic field parallel to the inplane of film at room temp. The magnetoconductance ratio decreases as the increase of voltage. It was indicated that the origin of carrier charge in chlorophyll films should be different with the carrier charge injection (electron).

  5. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, N. R., E-mail: nybouda@iastate.edu; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  6. Investigation of the surface current excitation by a relativistic electron electromagnetic field

    International Nuclear Information System (INIS)

    Naumenko, G; Shevelev, M; Potylitsyn, A; Popov, Yu; Sukhikh, L

    2010-01-01

    Surface current method and pseudo-photon ones are widely used in the problems of diffraction and transition radiation of relativistic electron in conductive targets. The simple analysis disclosed the contradiction between these methods in respect to the surface current excitation on target surfaces. This contradiction was resolved experimentally by the measurement of a surface current on the upstream and downstream target surfaces in diffraction radiation geometry. The experimental test showed, that no surface current is induced on the target downstream surface under the influence of a relativistic electron electromagnetic field in contrast to the upstream surface. This is important for the understanding of a forward transition and diffraction radiation nature and electromagnetic field evolution in interaction processes.

  7. Plasma current sustained by fusion charged particles in a field reversed configuration

    International Nuclear Information System (INIS)

    Berk, H.L.; Momota, H.; Tajima, T.

    1987-04-01

    The distribution of energetic charged particles generated by thermonuclear fusion reactions in a field reversed configuration (FRC) are studied analytically and numerically. A fraction of the charged fusion products escapes directly while the others are trapped to form a directed particle flow parallel to the plasma current. It is shown that the resultant current density produced by these fusion charged particles can be comparable to background plasma current density that produces the original field reversed configuration in a D- 3 He reactor. Self-consistent equilibria arising from the currents of the background plasma and proton fusion products are constructed where the Larmor radius of the fusion product is of arbitrary size. Reactor relevant parameters are examined, such as how the fusion reactivity rate varies as a result of supporting the pressure associated with the fusion products. We also model the synchrotron emission from various pressure profiles and quantitatively show how synchrotron losses vary with different pressure profiles in an FRC configuration

  8. Harmonic current layer method for the design of superconducting quadrupole magnetic field

    International Nuclear Information System (INIS)

    Zizek, F.

    1977-01-01

    The magnetic field of a superconducting quadrupole is investigated by the method of harmonic current layers of cylindrical shape. The superconducting winding is replaced by a system of thin current layers with a harmonically distributed density of the surface current along the circumference. The effect of the outer ferromagnetic circuit with an arbitrary constant permeability over the cross section is replaced analogically. The resultant magnetic field is then given by the superposition of the contributions from the individual current layers. The calculation method can be modified for the selection of the geometry of the winding for the latter to meet the demand for the high homogeneity of the gradient of magnetic induction in the working space of the superconducting quadrupole. (author)

  9. Steady-state configurations of Dzyaloshinskii domain walls driven by field and current

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez-Tejerina, L., E-mail: luis.st@ee.uva.es [Departamento de Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Salamanca, 37011 Salamanca (Spain); Alejos, O. [Departamento de Electricidad y Electrónica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Martínez, E. [Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Salamanca, 37011 Salamanca (Spain)

    2017-02-01

    The dynamics of Dzyaloshinskii domain walls (DDW) in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy, for different values of both perpendicular field and longitudinal current excitation associated to the Spin-Hall effect, has been studied, taking into account different values of the interfacial Dzyaloshinskii-Moriya interaction (DMI). This study has been carried out with the help of the q-Φ one-dimensional model and micromagnetic simulations. We have found that Walker breakdown may be avoided by applying a certain threshold current, even though the inverse effect is also possible. We have also found that, for particular values of field and current, the magnetization within the DDW experiences an abrupt change of orientation, which provokes a change on the contribution of current to the terminal DDW velocity. This effect disappears for sufficiently strong DMI, as it is expected from the model. - Highlights: • Steady-state configurations of Dzyaloshinskii domain walls driven by field and current have been reported. • Field-like torques and Slonczewskii-like torques due to spin-orbit interactions have been considered. • The response is associated with the rotation of the domain wall inner magnetization. • An asymmetric behavior arising from the existence of degenerate states is shown. • The asymmetry results in different travelled distances and/or terminal speeds.

  10. Steady-state configurations of Dzyaloshinskii domain walls driven by field and current

    International Nuclear Information System (INIS)

    Sánchez-Tejerina, L.; Alejos, O.; Martínez, E.

    2017-01-01

    The dynamics of Dzyaloshinskii domain walls (DDW) in ultrathin ferromagnetic strips with perpendicular magnetic anisotropy, for different values of both perpendicular field and longitudinal current excitation associated to the Spin-Hall effect, has been studied, taking into account different values of the interfacial Dzyaloshinskii-Moriya interaction (DMI). This study has been carried out with the help of the q-Φ one-dimensional model and micromagnetic simulations. We have found that Walker breakdown may be avoided by applying a certain threshold current, even though the inverse effect is also possible. We have also found that, for particular values of field and current, the magnetization within the DDW experiences an abrupt change of orientation, which provokes a change on the contribution of current to the terminal DDW velocity. This effect disappears for sufficiently strong DMI, as it is expected from the model. - Highlights: • Steady-state configurations of Dzyaloshinskii domain walls driven by field and current have been reported. • Field-like torques and Slonczewskii-like torques due to spin-orbit interactions have been considered. • The response is associated with the rotation of the domain wall inner magnetization. • An asymmetric behavior arising from the existence of degenerate states is shown. • The asymmetry results in different travelled distances and/or terminal speeds.

  11. Radio-frequency current drive efficiency in the presence of ITBs and a dc electric field

    Science.gov (United States)

    Rosa, P. R. da S.; Mourão, R.; Ziebell, L. F.

    2009-05-01

    This paper discusses the current drive efficiency by the combined action of EC and LH waves in the presence of a dc electric field and transport, with an internal transport barrier. The transport is assumed to be produced by magnetic fluctuations. The study explores the different barrier parameters and their influence on the current drive efficiency. We study the subject by numerically solving the Fokker-Planck equation. Our main result is that the barrier depth and barrier width are important to determine the correct shape of the current density profile but not to determine the current drive efficiency, which is very little influenced by these parameters. We also found similar results for the influence of the level of magnetic fluctuations on the current density profile and on the current drive efficiency.

  12. Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

    International Nuclear Information System (INIS)

    Catapano, F.; Zimbardo, G.; Artemyev, A. V.; Vasko, I. Y.

    2015-01-01

    We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed

  13. Current sheets with inhomogeneous plasma temperature: Effects of polarization electric field and 2D solutions

    Energy Technology Data Exchange (ETDEWEB)

    Catapano, F., E-mail: menacata3@gmail.com; Zimbardo, G. [Dipartimento di Fisica, Università della Calabria, Rende, Cosenza (Italy); Artemyev, A. V., E-mail: ante0226@gmail.com; Vasko, I. Y. [Space Research Institute, RAS, Moscow (Russian Federation)

    2015-09-15

    We develop current sheet models which allow to regulate the level of plasma temperature and density inhomogeneities across the sheet. These models generalize the classical Harris model via including two current-carrying plasma populations with different temperature and the background plasma not contributing to the current density. The parameters of these plasma populations allow regulating contributions of plasma density and temperature to the pressure balance. A brief comparison with spacecraft observations demonstrates the model applicability for describing the Earth magnetotail current sheet. We also develop a two dimensional (2D) generalization of the proposed model. The interesting effect found for 2D models is the nonmonotonous profile (along the current sheet) of the magnetic field component perpendicular to the current sheet. Possible applications of the model are discussed.

  14. Radio-frequency current drive efficiency in the presence of ITBs and a dc electric field

    International Nuclear Information System (INIS)

    Rosa, P.R. da S; Mourao, R.; Ziebell, L.F.

    2009-01-01

    This paper discusses the current drive efficiency by the combined action of EC and LH waves in the presence of a dc electric field and transport, with an internal transport barrier. The transport is assumed to be produced by magnetic fluctuations. The study explores the different barrier parameters and their influence on the current drive efficiency. We study the subject by numerically solving the Fokker-Planck equation. Our main result is that the barrier depth and barrier width are important to determine the correct shape of the current density profile but not to determine the current drive efficiency, which is very little influenced by these parameters. We also found similar results for the influence of the level of magnetic fluctuations on the current density profile and on the current drive efficiency.

  15. Measuring Plasma Formation Field Strength and Current Loss in Pulsed Power Diodes

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Mark D. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Patel, Sonal G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Falcon, Ross Edward [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Cartwright, Keith [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Kiefer, Mark L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Cuneo, Michael E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Radiographic Technologies Dept.; Maron, Yitzhak [Weizmann Inst. of Science, Rehovot (Israel)

    2017-11-01

    This LDRD investigated plasma formation, field strength, and current loss in pulsed power diodes. In particular the Self-Magnetic Pinch (SMP) e-beam diode was studied on the RITS-6 accelerator. Magnetic fields of a few Tesla and electric fields of several MV/cm were measured using visible spectroscopy techniques. The magnetic field measurements were then used to determine the current distribution in the diode. This distribution showed that significant beam current extends radially beyond the few millimeter x-ray focal spot diameter. Additionally, shielding of the magnetic field due to dense electrode surface plasmas was observed, quantified, and found to be consistent with the calculated Spitzer resistivity. In addition to the work on RITS, measurements were also made on the Z-machine looking to quantify plasmas within the power flow regions. Measurements were taken in the post-hole convolute and final feed gap regions on Z. Dopants were applied to power flow surfaces and measured spectroscopically. These measurements gave species and density/temperature estimates. Preliminary B-field measurements in the load region were attempted as well. Finally, simulation work using the EMPHASIS, electromagnetic particle in cell code, was conducted using the Z MITL conditions. The purpose of these simulations was to investigate several surface plasma generations models under Z conditions for comparison with experimental data.

  16. High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array.

    Science.gov (United States)

    Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao; Luo, Hang

    2018-02-01

    Polymer-based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400-600 kV mm -1 , which may bring more challenges relating to the failure probability. Here, a simple two-step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm -3 is achieved at low electric fields, i.e., 143 kV mm -1 , which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm -2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis.

  17. Cosmological information in the intrinsic alignments of luminous red galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Chisari, Nora Elisa [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States); Dvorkin, Cora, E-mail: nchisari@astro.princeton.edu, E-mail: cdvorkin@ias.edu [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States)

    2013-12-01

    The intrinsic alignments of galaxies are usually regarded as a contaminant to weak gravitational lensing observables. The alignment of Luminous Red Galaxies, detected unambiguously in observations from the Sloan Digital Sky Survey, can be reproduced by the linear tidal alignment model of Catelan, Kamionkowski and Blandford (2001) on large scales. In this work, we explore the cosmological information encoded in the intrinsic alignments of red galaxies. We make forecasts for the ability of current and future spectroscopic surveys to constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations (BAO) in the cross-correlation function of intrinsic alignments and the galaxy density field. For the Baryon Oscillation Spectroscopic Survey, we find that the BAO signal in the intrinsic alignments is marginally significant with a signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic survey following the EUCLID redshift selection function, we find signal-to-noise ratios of 12 and 15, respectively. Local type primordial non-Gaussianity, parametrized by f{sub NL} = 10, is only marginally significant in the intrinsic alignments signal with signal-to-noise ratios < 2 for the three surveys considered.

  18. Geometric corrections due to inhomogeneous field in the magnetospheric double current layer

    International Nuclear Information System (INIS)

    Callebaut, D.K.; Van den Buys, A.M.

    1985-01-01

    The case of oblique incidence and of a slope in the magnetic field for plane parallel models of the magnetospheric double layer is considered. The two models are the Magnetospheric Double Layer (MDL) and the Magnetospheric Double Current Layer (MDCL). The latter is more appropriate but due to some approximations it gives sometimes incorrect results. An improved model uses a triple current layer. (R.P.)

  19. Evaluation of the conditions of operation of X-ray equipment as regards the coincidence between light field, radiation field and the central ray alignment in radiology services of the Recife, Brazil

    International Nuclear Information System (INIS)

    Oliveira, Claudia F.M.; Silva, Iran J.O.; Lopes Filho, Ferdinand J.; Morais, Carolinne S.; Junior, Claudio L.R.

    2014-01-01

    This paper aims at considering the need for constant evaluation of diagnostic radiology equipment and the fact that this issue be part of the radiology technologist's tasks, develop skills in radiology technologist through applying quality control tests, as regards the assessment of coincidence between the light field and the radiation field and the alignment of the radiation beam of medical X-ray equipment in radiology services in the city of Recife. For the tests, the procedures by national protocols of Quality Control Tests were adopted - QCT and the Medical Radiodiagnosis Manual. The instruments used to check the alignment of the central ray was an acrylic cylinder with steel balls of 0.8 mm diameter located in the upper and lower base separated by a distance of 15 cm, a chassis loaded with film, tape and level bubble. The results show that the tested devices are in good condition for diagnostic radiology, with regard to both the radiation field to be exposed as well as the image quality for a more accurate diagnosis, which guarantees the individual radiological protection

  20. A tripolar current-steering stimulator ASIC for field shaping in deep brain stimulation.

    Science.gov (United States)

    Valente, Virgilio; Demosthenous, Andreas; Bayford, Richard

    2012-06-01

    A significant problem with clinical deep brain stimulation (DBS) is the high variability of its efficacy and the frequency of side effects, related to the spreading of current beyond the anatomical target area. This is the result of the lack of control that current DBS systems offer on the shaping of the electric potential distribution around the electrode. This paper presents a stimulator ASIC with a tripolar current-steering output stage, aiming at achieving more selectivity and field shaping than current DBS systems. The ASIC was fabricated in a 0.35-μ m CMOS technology occupying a core area of 0.71 mm(2). It consists of three current sourcing/sinking channels. It is capable of generating square and exponential-decay biphasic current pulses with five different time constants up to 28 ms and delivering up to 1.85 mA of cathodic current, in steps of 4 μA, from a 12 V power supply. Field shaping was validated by mapping the potential distribution when injecting current pulses through a multicontact DBS electrode in saline.