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1

A Free Jet Hg Target Operating in a High Magnetic Field Intersecting  

E-print Network

collider · Experiment approved by CERN Research Board - CERN designation nToF11 - Collaboration designation. DEPARTMENT OF ENERGY AccApp05 Participants · BNL, Princeton ­ project oversight, nozzle development, beam window design, optical diagnostics · MIT ­ magnet design & fabrication · ORNL ­ Hg target system design

McDonald, Kirk

2

Intersecting extended objects in supersymmetric field theories  

NASA Astrophysics Data System (ADS)

We show that there are three cases for which the generic intersections of p-dimensional extended object solutions of a supersymmetric field theory in a d-dimensional space-time are stringlike. They are (i) d = 4, p = 2, (ii) d = 6, p = 3 and (iii) d = 10, p = 5. By consideration of the topological charges associated with these objects we obtain a necessary condition for stable stringlike intersections to occur, a condition that is satisfied by the first two cases but not the third, which may have implications for the "heterotic 5-branes" recently discussed by Strominger. For case (i) we show by an analysis of the d = 4 Wess-Zumino model that stringlike intersections of domain walls can indeed occur.

Abraham, E. R. C.; Townsend, P. K.

1991-03-01

3

Do intense electromagnetic fields annihilate/create conical intersections?  

PubMed

In this article the authors relate the possibility that an intense electric field affects topological features of a molecular system. For this purpose they studied a model based on the Mathieu equation. They found that such a field may affect the spatial distribution of the nonadiabatic coupling terms but not the position of the intersections. In other words an intense electric field does not create or annihilate conical intersections. It is shown that this conclusion is valid as long as the field is an analytic function of the coordinates in the region of interest. These findings can be extended to magnetic fields (or electromagnetic fields) as long as they are analytic functions in the region of interest. PMID:17212489

Sarkar, Biplab; Adhikari, Satrajit; Baer, Michael

2007-01-01

4

Magnetic Fields  

NSDL National Science Digital Library

This page and its annex describes, in trivial terms, the physics of magnetic fields and the history of its discovery. Included is the work of Halley, Oersted, Ampere and Maxwell. It also describes a way of demonstrating it in the classroom, using a vu-graph projector. Later sections #5, #5a and #6 extend this to magnetic field lines and electromagnetism.

Stern, David

2005-01-04

5

ATOMIC INTERSECTION OF -FIELDS AND SOME OF ITS CONSEQUENCES  

E-print Network

ATOMIC INTERSECTION OF -FIELDS AND SOME OF ITS CONSEQUENCES PATRIZIA BERTI, LUCA PRATELLI generated by G and those sets F F satisfying P(F) {0, 1}. Conditions for P to be atomic on k i=1Ai, with A on atomicity of P on D. In fact, atomicity of P|D (i.e., the restriction of P to D) has implications in each

Berti, Patrizia

6

Magnetic Field Safety Magnetic Field Safety  

E-print Network

Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain medical conditions such as pacemakers, magnetic implants, or embedded shrapnel. In addition, high magnetic

McQuade, D. Tyler

7

Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism  

E-print Network

Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism Greg Friedman Texas the Witt condi- tion for intersection homology Poincar´e duality with respect to certain fields but not others. We then compute the bordism theory of K-Witt spaces for an arbitrary field K, extending results

Friedman, Greg

8

Magnetic fields in astrophysics  

Microsoft Academic Search

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

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

1983-01-01

9

Magnetic field sensor  

NASA Astrophysics Data System (ADS)

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

Silva, Nicolas

2012-09-01

10

Exploring Magnetic Fields  

NSDL National Science Digital Library

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

11

Magnetic fields of galaxies  

Microsoft Academic Search

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

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

1988-01-01

12

Facility Measures Magnetic Fields  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

13

Earths magnetic field  

Microsoft Academic Search

Recent studies of the Paleosecular Variation of lavas (PSVL) by the authors and others, shows that the variability of Earth's magnetic field over the last several million years is less than the variability of the present Earth's magnetic field. The present magnetic field is asymmetric between the northern and southern hemispheres. The dispersion in the southern hemisphere being much greater

N. Opdyke; V. Mejia

2003-01-01

14

The Magnetic Field  

NSDL National Science Digital Library

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

Barker, Jeffrey

15

Magnetic Fields Analogous to electric field, a magnet  

E-print Network

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

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

16

Corrigendum to "Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism"  

E-print Network

Corrigendum to "Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism" Greg Friedman August 14, 2012 The author's paper [2] concerns K-Witt spaces and, in particular, the correct results. Details can be found in [1]. If we consider K-Witt spaces and K-Witt bordism using K

Friedman, Greg

17

Mapping Magnetic Field Lines  

NSDL National Science Digital Library

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

18

The Magnetic Field  

NSDL National Science Digital Library

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

19

Magnetic Field Example 1  

NSDL National Science Digital Library

Clicking on the different links below will produce different magnetic fields in the box above. The wires (perpendicular to the screen) or coils (in and out of the screen) are not visible, but you can determine what they are from the field. You can also click on a point to read off the magnetic field at that place.

Christian, Wolfgang; Belloni, Mario

2008-02-19

20

Magnetic Field Distribution of Permanent Magnet Magnetized by Static Magnetic Field Generated by HTS Bulk Magnet  

Microsoft Academic Search

Demagnetized rare earth magnets (Nd-Fe-B) can be fully magnetized by scanning them in the intense static fields over 3 T of a HTS bulk magnet which was cooled to the temperature range lower than 77K with use of cryo-coolers and activated by the field of 5 T. We precisely examined the magnetic field distributions of magnetized permanent magnets. The magnetic

Tetsuo Oka; Nobutaka Kawasaki; Satoshi Fukui; Jun Ogawa; Takao Sato; Toshihisa Terasawa; Yoshitaka Itoh; Ryohei Yabuno

2012-01-01

21

Abstract: Quasistatic magnetic fields  

Microsoft Academic Search

A prototype switching system has been developed which can switch 20 kA at 230 V for short periods of time through inductive loads. High power silicon controlled rectifiers are used to switch the National Magnet Laboratory dc generators on and off into a liquid N2 cooled, low impedance high field magnet so that high fields can be generated for a

H. C. Praddaude; S. Foner

1979-01-01

22

Cosmic Magnetic Fields  

Microsoft Academic Search

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

Elisabete M. de Gouveia Dal Pino; Dal Pino

2006-01-01

23

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

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

Beck, Rainer

24

Interplanetary Magnetic Field Lines  

NSDL National Science Digital Library

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

Stern, David

2005-04-27

25

Magnetic Bar Field Model  

NSDL National Science Digital Library

The EJS Magnetic Bar Field Model shows the field of a bar magnet and has a movable compass that reports the magnetic field values. The bar magnet model is built by placing a group of magnetic dipoles along the bar magnet. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting Open Ejs Model from the pop-up menu item. The Magnetic Bar Field model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_MagneticBarField.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Franciscouembre; Cox, Anne

2009-09-18

26

Magnetic Fields, Flares & Forecasts  

Microsoft Academic Search

A 2D wavelet transform modulus maxima (WTMM) method is used to characterise the complexity of the distribution of the photospheric magnetic field of active regions. The WTMM method offers increased accuracy and reliability over previous fractal and multifractal methods. The multifractal spectrum of both quiet Sun and active region magnetic features are presented. It is shown that the multifractal nature

Paul A. Conlon; P. Kestener; R. McAteer; P. Gallagher

2009-01-01

27

The First Magnetic Fields  

E-print Network

We demonstrate that the Biermann battery mechanism for the creation of large scale magnetic fields can arise in a simple model protogalaxy. Analytic calculations and numerical simulations follow explicitly the generation of vorticity (and hence magnetic field) at the outward-moving shock that develops as the protogalactic perturbation collapses. Shear angular momentum then distorts this field into a dipole-like configuration. The magnitude of the field created in the fully formed disk galaxy is estimated to be 10^(-17) Gauss, approximately what is needed as a seed for the galactic dynamo.

George Davies; Lawrence M. Widrow

1999-12-14

28

Power spectra of the interplanetary magnetic field near the earth  

NASA Technical Reports Server (NTRS)

Power spectra of the interplanetary magnetic field measured by near-earth satellites upstream from the earth's bow shock are free from terrestrial contamination provided the field at the satellite does not intersect the bow shock. Considerable spectral enhancement for the range of frequencies 0.01 to 1.00 Hz, due to turbulence caused by the shock, may occur if the field observed at the satellite intersects the shock. This turbulence occurs frequently in both the morning and afternoon quadrants. In the frequency band from 0.07 to 1 Hz, this noise decreases in amplitude with radial distance from the shock with an attenuation length of 4 R sub E.

Childers, D. D.; Russell, C. T.

1972-01-01

29

Solar Wind Magnetic Fields  

NASA Technical Reports Server (NTRS)

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

Smith, E. J.

1995-01-01

30

Planetary magnetic fields  

Microsoft Academic Search

The past several years have seen dramatic developments in the study of planetary magnetic fields, including a wealth of new data, mainly from the Galilean satellites and Mars, together with major improvements in our theoretical modeling effort of the dynamo process believed responsible for large planetary fields. These dynamos arise from thermal or compositional convection in fluid regions of large

David J. Stevenson

2003-01-01

31

Graphene Magnetic Field Sensors  

Microsoft Academic Search

Graphene extraordinary magnetoresistance (EMR) devices have been fabricated and characterized in varying magnetic fields at room temperature. The atomic thickness, high carrier mobility and high current carrying capabilities of graphene are ideally suited for the detection of nanoscale sized magnetic domains. The device sensitivity can reach 10 mV\\/Oe, larger than state of the art InAs 2DEG devices of comparable size

Simone Pisana; Patrick M. Braganca; Ernesto E. Marinero; Bruce A. Gurney

2010-01-01

32

Magnetic Field and Life  

NSDL National Science Digital Library

This is a lesson where learners explore magnetic forces, fields, and the relationship between electricity. Learners will use this information to infer how the Earth generates a protective magnetic field. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes, prerequisite concepts, common misconceptions, student journal and reading. This is lesson seven in the Astro-Venture Geology Training Unit that were developed to increase students' awareness of and interest in astrobiology and the many career opportunities that utilize science, math and technology skills. The lessons are designed for educators to use with with the Astro-Venture multimedia modules.

33

Generalized random fields related to self-intersections of the Brownian motion  

PubMed Central

Let Tk?(?; t1,..., tk) = ?(Xt1)q?(Xt2 - Xt1)... q?(Xtk - Xtk-1), where Xt is a Brownian motion in R2, ?(dx) = ?(x)dx, and q? converges to Dirac's ? function as ? ? 0. The self-intersection local times of order k are described by a generalized random field Tk(?; t1,..., tk) = lim??0Tk?(?; t1,..., tk) for 0 < t1 <... < tk. The field blows up as ti - tj ? 0 for some i ? j. I show that with a proper choice of the coefficients Bkl(?), a generalized random field [unk] k(?; t1,..., tk) = lim??0 [Tk?(?; t1,..., tk) + ?l=1k-1 [Bkl(?)Tl?](?; t1,..., tk)] is well defined for all 0 ? t1 ?... ? tk and it coincides with Tk(?; t1,..., tk) for t1 <... < tk. PMID:16593700

Dynkin, E. B.

1986-01-01

34

High field superconducting magnets  

NASA Technical Reports Server (NTRS)

A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

2011-01-01

35

On magnetic field ``reconstruction''  

NASA Astrophysics Data System (ADS)

Context: Solanki and colleagues have presented intriguing 3D reconstructions of magnetic fields from the vector polarimetry of the He I 1083 nm multiplet. Aims: In this Research Note I re-examine the reconstruction technique used. Methods: Using a simple dipole field, I examine the reconstruction technique as applied to the theoretical fields. I assume that the He line forms in two locations, (1) along the magnetic loops and (2) in a horizontal plane. Results: The planar interpretation can account for all aspects of the data, but the loop interpretation has geometrical and physical problems. Conclusions: The data by themselves are not sufficient to determine which picture is more applicable. Nevertheless I argue that the planar interpretation makes more physical sense and that the early reconstructions lead to spurious results. I suggest additional tests that might help constrain the problem further.

Judge, P. G.

2009-01-01

36

Nuclear Magnetic Resonance and Magnetic Field Measurements  

NSDL National Science Digital Library

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

37

The Earth's Magnetic Field  

NSDL National Science Digital Library

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

Johnson, Roberta

2000-07-01

38

The Heliospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

The Heliospheric Magnetic Field (HMF) is the physical framework in which energetic particles and cosmic rays propagate. Changes in the large scale structure of the magnetic field lead to short- and long term changes in cosmic ray intensities, in particular in anti-phase with solar activity. The origin of the HMF in the corona is well understood and inner heliospheric observations can generally be linked to their coronal sources. The structure of heliospheric magnetic polarities and the heliospheric current sheet separating the dominant solar polarities are reviewed here over longer than a solar cycle, using the three dimensional heliospheric observations by Ulysses. The dynamics of the HMF around solar minimum activity is reviewed and the development of stream interaction regions following the stable flow patterns of fast and slow solar wind in the inner heliosphere is described. The complex dynamics that affects the evolution of the stream interaction regions leads to a more chaotic structure of the HMF in the outer heliosphere is described and discussed on the basis of the Voyager observations. Around solar maximum, solar activity is dominated by frequent transients, resulting in the interplanetary counterparts of Coronal Mass Ejections (ICMEs). These produce a complex aperiodic pattern of structures in the inner heliosphere, at all heliolatitudes. These structures continue to interact and evolve as they travel to the outer heliosphere. However, linking the observations in the inner and outer heliospheres is possible in the case of the largest solar transients that, despite their evolutions, remain recognizably large structures and lead to the formation of Merged Interaction Regions (MIRs) that may well form a quasi-spherical, "global" shell of enhanced magnetic fields around the Sun at large distances. For the transport of energetic particles and cosmic rays, the fluctuations in the magnetic field and their description in alternative turbulent models remains a very important research topic. These are also briefly reviewed in this paper.

Balogh, Andr; Erds, Gza

2013-06-01

39

Magnetic Fields, Flares & Forecasts  

NASA Astrophysics Data System (ADS)

A 2D wavelet transform modulus maxima (WTMM) method is used to characterise the complexity of the distribution of the photospheric magnetic field of active regions. The WTMM method offers increased accuracy and reliability over previous fractal and multifractal methods. The multifractal spectrum of both quiet Sun and active region magnetic features are presented. It is shown that the multifractal nature of the quiet Sun is significantly different from that of an active region. As such, a method is proposed to seperate the information corresponding to the multifractal spectrum of an active region from the surrounding quite Sun texture. The WTMM method and segmentation procedure are shown to detect the internal restructuring of active region magnetic features prior to flaring. We detect two thresholds (Haussdorf dimension > 1.2 and Holder Exponent > -0.7) as possible indicators for conditions favourable to flaring.

Conlon, Paul A.; Kestener, P.; McAteer, R.; Gallagher, P.

2009-05-01

40

Magnetic fields and cancer  

SciTech Connect

This letter is a response to an article by Savitz and Kaune, EHP 101:76-80. W-L wire code was applied to data from a 1988 Denver study, and an association was reported between high W-L wire code and childhood cancer. This author discusses several studies and provides explanations which weakens the argument that classification error resulted in an appreciable reduction in the association between W-L high wire code and childhood cancer. In conclusion, the fact that new wire code is only weakly correlated with magnetic field measurements (in the same manner as the original W-L wire code) suggests that the newly reported stronger association with childhood cancer is likely due to factors other than magnetic fields. Differential residential mobility and differential residential age are two possible explanations and are suggestive that the reported association may be false.

Jones, T.L.

1993-10-01

41

Magnetic Field of the Earth  

NSDL National Science Digital Library

Students can learn about how the magnetic field of the earth is similar to magnets. Go to the following link: Magnetic Field of the Earth 1. What makes the earth like a magnet? 2. How do we measure magnetism? Be sure to check out the fun games and activities on this web site too!! Now click on the following link and listen to a 2 minute presentation about magnetism: Pulse Planet Next go to ...

Merritt, Mrs.

2005-10-18

42

AC Magnetic Field Survey Report  

E-print Network

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

Krstic, Miroslav

43

The WIND magnetic field investigation  

Microsoft Academic Search

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

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

1995-01-01

44

Magnetic Field Topology in Jets  

NASA Technical Reports Server (NTRS)

We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

Gardiner, T. A.; Frank, A.

2000-01-01

45

Low field magnetic resonance imaging  

DOEpatents

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

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

2010-07-13

46

NMR at low magnetic fields  

NASA Astrophysics Data System (ADS)

NMR provides outstanding information in chemistry and in medicine. But the equipment is expensive as high-field magnets are employed. Low-field NMR works with inexpensive permanent magnets. Until recently these did not provide fields sufficiently homogeneous for spectroscopy and were mostly used for relaxation measurements. Relaxation can also be measured outside the magnet, and small mobile NMR devices have been developed for non-destructive testing of large objects. Today small stray-field magnets and small magnets with homogeneous fields are available for relaxation analysis, imaging, and spectroscopy. Their availability is believed to be essential for shifting NMR analysis from a specialist's tool to a convenience tool.

Blmich, Bernhard; Casanova, Federico; Appelt, Stephan

2009-08-01

47

Magnetic Fields in Irregular Galaxies  

E-print Network

Magnetic fields are an important component of the interstellar medium, especially in low-mass galaxies like irregulars where the magnetic pressure may be significant. However, few irregular galaxies have observed magnetic field structures. Using the VLA, the GBT, and the ATCA, we have observed several irregular galaxies in the radio continuum to determine their magnetic field structures. Here we report on our results for the galaxies NGC 4214 and NGC 1569.

Amanda A. Kepley; Stefanie Muehle; Eric M. Wilcots; John Everett; Ellen Zweibel; Timothy Robishaw; Carl Heiles

2007-08-24

48

Magnetic Fields in Protostellar Disks  

E-print Network

· Shear in disc may wind up field or drive MRI · Equipartition field in the minimum solar nebula to the shear in the disc? ­ which form of diffusion is dominant? logn/nH (s-1) M+ C+ m+ e He+ H+ H3 instability (MRI) ­ disc-driven winds Magnetic fields · Magnetic fields play an important role during star

Wardle, Mark

49

The Heliospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

The heliospheric magnetic field (HMF) is the extension of the coronal magnetic field carried out into the solar system by the solar wind. It is the means by which the Sun interacts with planetary magnetospheres and channels charged particles propagating through the heliosphere. As the HMF remains rooted at the solar photosphere as the Sun rotates, the large-scale HMF traces out an Archimedean spiral. This pattern is distorted by the interaction of fast and slow solar wind streams, as well as the interplanetary manifestations of transient solar eruptions called coronal mass ejections. On the smaller scale, the HMF exhibits an array of waves, discontinuities, and turbulence, which give hints to the solar wind formation process. This review aims to summarise observations and theory of the small- and large-scale structure of the HMF. Solar-cycle and cycle-to-cycle evolution of the HMF is discussed in terms of recent spacecraft observations and pre-spaceage proxies for the HMF in geomagnetic and galactic cosmic ray records.

Owens, Mathew J.; Forsyth, Robert J.

2013-11-01

50

Photonic Magnetic Field Sensor  

NASA Astrophysics Data System (ADS)

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

Wyntjes, Geert

2002-02-01

51

Magnetic Fields: Visible and Permanent.  

ERIC Educational Resources Information Center

Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

Winkeljohn, Dorothy R.; Earl, Robert D.

1983-01-01

52

(version 6/26/06) Magnetic Fields  

E-print Network

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

Collins, Gary S.

53

Magnetic Propeller for Uniform Magnetic Field Levitation  

E-print Network

Three new approaches to generating thrust in uniform magnetic fields are proposed. The first direction is based on employing Lorentz force acting on partial magnetically shielded 8-shaped loop with current in external magnetic field, whereby a net force rather than a torque origins. Another approach, called a Virtual Wire System, is based on creating a magnetic field having an energetic symmetry (a virtual wire), with further superposition of external field. The external field breaks the symmetry causing origination of a net force. Unlike a wire with current, having radial energetic symmetry, the symmetry of the Virtual Wire System is closer to an axial wire. The third approach refers to the first two. It is based on creation of developed surface system, comprising the elements of the first two types. The developed surface approach is a way to drastically increase a thrust-to-weight ratio. The conducted experiments have confirmed feasibility of the proposed approaches.

Mark Krinker; Alexander Bolonkin

2008-07-12

54

NATIONAL HIGH MAGNETIC FIELD LABORATORY  

E-print Network

and testing areas, magnet experiment cells, and laser laboratory areas. The laboratory is used 24 hours perNATIONAL HIGH MAGNETIC FIELD LABORATORY NHMFL FLORIDA STATE UNIVERSITY SAFETY PROCEDURE SP-3 TITLE Dalton ______________________________________________________ ASSISTANT DIRECTOR, ENVIRONMENTAL, HEALTH

Weston, Ken

55

Understanding the Chromospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

The chromospheric magnetic field is an important and essential component for understanding solar atmospheric fields. Due to the problems of polarization radiation transfer in the chromosphere and the low detective sensitivity of chromospheric spectrum lines, observations of chromospheric magnetic fields are very difficult, so studies of chromospheric fields are infrequent. However, the understanding of chromospheric fields is evolving. In this report, we summarize our current empirical knowledge and basic physical understanding of chromospheric fields. We concentrate on the comparison of magnetic fields in the photosphere and chromosphere, and then display their difference.

Jin, C. L.; Harvey, J. W.; Pietarila, A.

2014-10-01

56

Reconnection of Magnetic Fields  

NASA Astrophysics Data System (ADS)

Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Bchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

Birn, J.; Priest, E. R.

2007-01-01

57

Exposure guidelines for magnetic fields  

SciTech Connect

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

Miller, G.

1987-12-01

58

Magnetic-field-dosimetry system  

DOEpatents

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

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

1981-01-21

59

Magnetic fields in massive stars  

E-print Network

Although indirect evidence for the presence of magnetic fields in high-mass stars is regularly reported in the literature, the detection of these fields remains an extremely challenging observational problem. We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

S. Hubrig

2007-03-09

60

The Galileo magnetic field investigation  

Microsoft Academic Search

The Galileo Orbiter carries a complement of fields and particles instruments designed to provide data needed to shed light on the structure and dynamical variations of the Jovian magnetosphere. Many questions remain regarding the temporal and spatial properties of the magnetospheric magnetic field, how the magnetic field maintains corotation of the embedded plasma and the circumstances under which corotation breaks

M. G. Kivelson; K. K. Khurana; J. D. Means; C. T. Russell; R. C. Snare

1992-01-01

61

Mars Observer magnetic fields investigation  

NASA Technical Reports Server (NTRS)

The magnetic fields experiment designed for the Mars Observer mission will provide definitive measurements of the Martian magnetic field from the transition and mapping orbits planned for the Mars Observer. The paper describes the instruments (which include a classical magnetometer and an electron reflection magnetometer) and techniques designed to investigate the nature of the Martian magnetic field and the Mars-solar wind interaction, the mapping of crustal magnetic fields, and studies of the Martian ionosphere, which are activities included in the Mars Observer mission objectives. Attention is also given to the flight software incorporated in the on-board data processor, and the procedures of data processing and analysis.

Acuna, M. H.; Connerney, J. E. P.; Wasilewski, P.; Lin, R. P.; Anderson, K. A.; Carlson, C. W.; Mcfadden, J.; Curtis, D. W.; Reme, H.; Cros, A.

1992-01-01

62

(Revised December 30, 2013) Magnetic Fields  

E-print Network

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

Collins, Gary S.

63

Magnetic response to applied electrostatic field in external magnetic field  

NASA Astrophysics Data System (ADS)

We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

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

2014-04-01

64

Theory of fossil magnetic field  

E-print Network

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

Dudorov, Alexander E

2014-01-01

65

Origin of cosmic magnetic fields.  

PubMed

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

Campanelli, Leonardo

2013-08-01

66

NATIONAL HIGH MAGNETIC FIELD LABORATORY  

E-print Network

NATIONAL HIGH MAGNETIC FIELD LABORATORY SUPPORTED BY: THE NATIONAL SCIENCE FOUNDATION and THE STATE OF FLORIDA OPERATED BY: FLORIDA STATE UNIVERSITY · UNIVERSITY OF FLORIDA · LOS ALAMOS NATIONAL LABORATORY Page 15 2005 ANNUAL REPORT #12;2005 ANNUAL REPORT National High magnetic Field Laboratory 2005 NHMFL

Weston, Ken

67

Magnetic Field Problem: Measuring Current  

NSDL National Science Digital Library

A cross section of two circular wire loops carrying the exact same current is shown above (position given in centimeters and magnetic field given in milli-Tesla). You can click-drag to read the magnitude of the magnetic field.

Christian, Wolfgang; Belloni, Mario

2007-03-03

68

The effects of pseudo magnetic fields in molecular spectra and scattering  

SciTech Connect

Pseudo magnetic fields appear in the Born-Oppenheimer method for molecules when conical intersections or electronic angular momenta are taken into account. These fields are not real magnetic fields but they have the same mathematical properties and can lead to real observable effects in the dynamics of molecules. A general vector potential (gauge theory) approach for including these field effects in the Born-Oppenheimer method is introduced and applied to H + O{sub 2} scattering and the vibrational spectrum of Na{sub 3}(X) for zero total angular momentum (J = 0). The scattering results for HO{sub 2} show significant shifts in the resonance energies and lifetimes due to a magnetic solenoid type field originating from the C{sub 2v} conical intersection in HO{sub 2}. Significant changes in the state-to-state transition probabilities are also observed. The non-degenerate A{sub 1} and A{sub 2} vibrational spectra of Na{sub 3}(X) show significant shifts in the energy levels due to a magnetic solenoid type field originating from the D{sub 3h} conical intersection in Na{sub 3}. These two examples show that the effects of pseudo magnetic fields can be significant and in many cases they must be included in order to obtain agreement between theory and experiment. The newly developed gauge theory techniques for treating pseudo magnetic fields are also relevant for including the effects of real magnetic fields.

Kendrick, B. [Los Alamos National Lab., NM (United States). Theoretical Div.

1996-12-31

69

CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Structure of Magnetic  

E-print Network

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

Callen, James D.

70

Magnetic Field Measurements in Beam Guiding Magnets  

E-print Network

Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as well as the recently developed method of beam based alignment. References of historical nature as well as citations of recent work are given. The present commercial availability of the different sensors and asso-ciated equipment is indicated. Finally we shall try to analyze possible future needs for developments in those fields.

Henrichsen, K N

1998-01-01

71

Kinematics at the intersection of the Garlock and Death Valley fault zones, California: Integration of TM data and field studies  

NASA Technical Reports Server (NTRS)

The Garlock and Death Valley fault zones in SE California are two active strike-slip faults coming together on the east side of the Avawatz Mtns. The kinematics of this intersection, and the possible continuation of either fault zone, are being investigated using a combination of field mapping, and processing and interpretation of remotely sensed image data. Regional and local relationships are derivable from Thematic Mapper data (30 m resolution), including discrimination and relative age dating of alluvial fans, bedrock mapping, and fault mapping. Aircraft data provide higher spatial resolution over more limited areas. Hypotheses being considered are: (1) the Garlock fault extends east of the intersection; (2) the Garlock fault terminates at the intersection and the Death Valley fault continues southeastward; and (3) the Garlock fault has been offset right laterally by the Death Valley fault which continues to the southeast. Preliminary work indicates that the first hypothesis is invalid. From kinematic considerations, image analysis, and field work the third hypothesis is favored. The projected continuation of the Death Valley zone defines the boundary between the Mojave crustal block and the Basin and Range block.

Abrams, Michael; Verosub, Ken; Finnerty, Tony; Brady, Roland

1987-01-01

72

Field measurement of nitromethane from automotive emissions at a busy intersection using proton-transfer-reaction mass spectrometry  

NASA Astrophysics Data System (ADS)

Field measurements of seven nitro-organic compounds including nitromethane and ten related volatile organic compounds were carried out using proton-transfer-reaction mass spectrometry at a busy intersection of an urban city, Kawasaki, Japan from 26th February to 6th March, 2011. Among the nitro-organic compounds, nitromethane was usually observed along with air pollutants emitted from automobiles. The mixing ratios of nitromethane varied substantially and sometimes clearly varied at an approximately constant interval. The interval corresponded to the cycle of the traffic signals at the intersection and the regular peaks of nitromethane concentrations were caused by emissions from diesel trucks running with high speed. In addition to the regular peaks, sharp increases of nitromethane concentrations were often observed irregularly from diesel trucks accelerating in front of the measurement site. For other nitro-organic compounds such as nitrophenol, nitrocresol, dihydroxynitrobenzene, nitrobenzene, nitrotoluene, and nitronaphthalene, most of the data fluctuated within the detection limits.

Inomata, Satoshi; Fujitani, Yuji; Fushimi, Akihiro; Tanimoto, Hiroshi; Sekimoto, Kanako; Yamada, Hiroyuki

2014-10-01

73

Preflare magnetic and velocity fields  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

74

Streamer propagation in magnetic field  

E-print Network

The propagation of a streamer near an insulating surface under the influence of a transverse magnetic field is theoretically investigated. In the weak magnetic field limit it is shown that the trajectory of the streamer has a circular form with a radius that is much larger than the cyclotron radius of an electron. The charge distribution within the streamer head is strongly polarized by the Lorentz force exerted perpendicualr to the streamer velocity. A critical magnetic field for the branching of a streamer is estimated. Our results are in good agreement with available experimental data.

Zhuravlev, V N; Vagner, I D; Wyder, P

1997-01-01

75

AC photovoltaic module magnetic fields  

SciTech Connect

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

Jennings, C.; Chang, G.J. [Pacific Gas and Electric Co., San Francisco, CA (United States); Reyes, A.B.; Whitaker, C.M. [Endecon Engineering, San Ramon, CA (United States)

1997-12-31

76

Investigating Magnetic Force Fields  

NSDL National Science Digital Library

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

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

2012-03-18

77

Neutron scattering in magnetic fields  

SciTech Connect

The use of magnetic fields in neutron scattering experimentation is reviewed briefly. Two general areas of application can be distinguished. In one the field acts to change the properties of the scattering sample; in the second the field acts on the neutron itself. Several examples are discussed. Precautions necessary for high precision polarized beam measurements are reviewed. 33 references.

Koehler, W.C.

1984-01-01

78

N-flationary magnetic fields  

NASA Astrophysics Data System (ADS)

There is increasing interest in the role played by pseudo Nambu Goldstone bosons (pNGBs) in the construction of string-inspired models of inflation. In these models the inflaton is expected to be coupled to gauge fields, and will lead to the generation of magnetic fields that can be of cosmological interest. We study the production of such fields mainly focusing on the model of N-flation, where the collective effect of several pNGBs drives inflation. Because the fields produced are maximally helical, inverse cascade processes in the primordial plasma significantly increase their coherence length. We discuss under what conditions inflation driven by pNGBs can account for the cosmological magnetic fields observed. A constraint on the parameters of this class of inflationary scenarios is also derived by requiring that the magnetic field does not backreact on the inflating background.

Anber, Mohamed M.; Sorbo, Lorenzo

2006-10-01

79

Field of the Magnetic Monopole  

E-print Network

This paper shows that based upon the Helmholtz decomposition theorem the field of a stationary magnetic monopole, assuming it exists, cannot be represented by a vector potential. Persisting to use vector potential in monopole representation violates fundamentals of mathematics. The importance of this finding is that the vector potential representation was crucial to the original prediction of the quantized value for a magnetic charge.

A. R. Hadjesfandiari

2007-01-19

80

Neutron in Strong Magnetic Fields  

E-print Network

Relativistic world-line Hamiltonian for strongly interacting 3q systems in magnetic field is derived from the path integral for the corresponding Green's function. The neutral baryon Hamiltonian in magnetic field obeys the pseudomomentum conservation and allows a factorization of the c.m. and internal motion. The resulting expression for the baryon mass in magnetic field is written explicitly with the account of hyperfine, OPE and OGE (color Coulomb) interaction. The neutron mass is fast decreasing with magnetic field, losing 1/2 of its value at eB~0.25 GeV^2 and is nearly zero at eB~0.5 GeV^2. Possible physical consequences of the calculated mass trajectory of the neutron, M_n(B), are presented and discussed.

M. A. Andreichikov; B. O. Kerbikov; V. D. Orlovsky; Yu. A. Simonov

2013-12-08

81

Review of magnetic field observations  

NASA Technical Reports Server (NTRS)

Recent observations of magnetic fields in the magnetosphere are reviewed, and critical experiments and data are identified for theoretical analysis and interpretation. Quantitative studies of the solar wind interaction with the earth's magnetic field, regional measurements near the earth's equator at R = 2-8 R sub E, the polar cusp region of the geomagnetosphere, and structural models of the neutral sheet region in the geomagnetic tail are considered.

Ness, N. F.

1971-01-01

82

Chiral transition with magnetic fields  

E-print Network

We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling constants and the number of fermions. We show that the critical temperature for the restoration of chiral symmetry monotonically increases from small to intermediate values of the magnetic fields and that this temperature is always above the critical temperature for the case when the magnetic field is absent.

Alejandro Ayala; Luis Alberto Hernandez; Ana Julia Mizher; Juan Cristobal Rojas; Cristian Villavicencio

2014-04-25

83

Optical sensor of magnetic fields  

DOEpatents

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

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

1986-03-25

84

Magnetic field induced dynamical chaos  

SciTech Connect

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

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

2013-12-15

85

Magnetic fields in protoplanetary disks  

E-print Network

Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary discs. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface, and magnetically-driven mixing has implications for disk chemistry and evolution of the grain population. However, the weak ionisation of protoplanetary discs means that magnetic fields may not be able to effectively couple to the matter. I present calculations of the ionisation equilibrium and magnetic diffusivity as a function of height from the disk midplane at radii of 1 and 5 AU. Dust grains tend to suppress magnetic coupling by soaking up electrons and ions from the gas phase and reducing the conductivity of the gas by many orders of magnitude. However, once grains have grown to a few microns in size their effect starts to wane and magnetic fields can begin to couple to the gas even at the disk midplane. Because ions are generally decoupled from the magnetic field by neutral collisions while electrons are not, the Hall effect tends to dominate the diffusion of the magnetic field when it is able to partially couple to the gas. For a standard population of 0.1 micron grains the active surface layers have a combined column of about 2 g/cm^2 at 1 AU; by the time grains have aggregated to 3 microns the active surface density is 80 g/cm^2. In the absence of grains, x-rays maintain magnetic coupling to 10% of the disk material at 1 AU (150 g/cm^2). At 5 AU the entire disk thickness becomes active once grains have aggregated to 1 micron in size.

Mark Wardle

2007-04-07

86

Active Region Magnetic Fields. I. Plage Fields  

Microsoft Academic Search

We present observations taken with the Advanced Stokes Polarimeter (ASP) in active-region plages and study the frequency distribution of the magnetic field strength (B), inclination with respect to vertical ( gamma ), azimuthal orientation ( chi ), and filling factor (f). The most common values at disk center are B = 1400 G, gamma < 10 deg, no preferred east-west

V. Martinez Pillet; B. W. Lites; A. Skumanich

1997-01-01

87

Magnetic fields in O stars  

NASA Astrophysics Data System (ADS)

During the last decade, large-scale, organized (generally dipolar) magnetic fields with strengths between 0.1 and 20 kG have been detected in dozens of OB stars. This contribution reviews the impact of such fields on the stellar winds of O-type stars, with emphasis on variability and X-ray emission.

Naz, Y.

2014-11-01

88

Magnetization and rotation of MTG HTSC ring in magnetic field  

Microsoft Academic Search

The magnetization of a melt-texture growth (MTG) HTSC ring has been studied. It is shown that the magnetic field inside the ring is larger than the external field under a certain range of external magnetic fields. We have also investigated the magnetic field dependence of the response of a detective coil near a rotating superconducting ring. The responses of the

E. V. Postrekhin; L. W. Zhou; K. J. Huang; C. B. Cai; S. M. Gong; Y. X. Fu

1996-01-01

89

Enhancement of strong-field multiple ionization in the vicinity of the conical intersection in 1,3-cyclohexadiene ring opening  

SciTech Connect

Nonradiative energy dissipation in electronically excited polyatomic molecules proceeds through conical intersections, loci of degeneracy between electronic states. We observe a marked enhancement of laser-induced double ionization in the vicinity of a conical intersection during a non-radiative transition. We measured double ionization by detecting the kinetic energy of ions released by laser-induced strong-field fragmentation during the ring-opening transition between 1,3-cyclohexadiene and 1,3,5-hexatriene. The enhancement of the double ionization correlates with the conical intersection between the HOMO and LUMO orbitals.

Petrovic, Vladimir S., E-mail: petrovic@stanford.edu; Kim, Jaehee [Department of Physics, Stanford University, Stanford, California 94305 (United States) [Department of Physics, Stanford University, Stanford, California 94305 (United States); The Stanford PULSE Institute, Menlo Park, California 94025 (United States); Schorb, Sebastian [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)] [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); White, James [The Stanford PULSE Institute, Menlo Park, California 94025 (United States) [The Stanford PULSE Institute, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Cryan, James P.; Zipp, Lucas [Department of Physics, Stanford University, Stanford, California 94305 (United States) [Department of Physics, Stanford University, Stanford, California 94305 (United States); The Stanford PULSE Institute, Menlo Park, California 94025 (United States); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Glownia, J. Michael; Broege, Douglas [The Stanford PULSE Institute, Menlo Park, California 94025 (United States) [The Stanford PULSE Institute, Menlo Park, California 94025 (United States); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Miyabe, Shungo; Tao, Hongli [The Stanford PULSE Institute, Menlo Park, California 94025 (United States) [The Stanford PULSE Institute, Menlo Park, California 94025 (United States); Department of Chemistry, Stanford University, Stanford, California 94305 (United States); Martinez, Todd [The Stanford PULSE Institute, Menlo Park, California 94025 (United States) [The Stanford PULSE Institute, Menlo Park, California 94025 (United States); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Chemistry, Stanford University, Stanford, California 94305 (United States); Bucksbaum, Philip H. [Department of Physics, Stanford University, Stanford, California 94305 (United States) [Department of Physics, Stanford University, Stanford, California 94305 (United States); The Stanford PULSE Institute, Menlo Park, California 94025 (United States); SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)

2013-11-14

90

Magnetic field investigations on low cost missions  

Microsoft Academic Search

Magnetic fields pervade all of space and provide important diagnostic information on the nature of processes occurring within and around solar system objects. Thus magnetic investigations are frequently included on planetary missions. Since spacecraft subsystems can generate magnetic fields that may interfere with the measurement of the ambient field, magnetic cleanliness programs are usually instituted to minimize such extraneous magnetic

R. C. Snare; C.T. Russell

1995-01-01

91

Indoor localization using magnetic fields  

NASA Astrophysics Data System (ADS)

Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing hallways with different kinds of pillars, doors and elevators. All in all, this dissertation contributes the following: 1) provides a framework for understanding the presence of ambient magnetic fields indoors and utilizing them to solve the indoor localization problem; 2) develops an application that is independent of the user and the smart phones and 3) requires no other infrastructure since it is deployed on a device that encapsulates the sensing, computing and inferring functionalities, thereby making it a novel contribution to the mobile and pervasive computing domain.

Pathapati Subbu, Kalyan Sasidhar

92

Mars Crustal Magnetic Field Remnants  

NASA Technical Reports Server (NTRS)

The radial magnetic field measured is color coded on a global perspective view that shows measurements derived from spacecraft tracks below 200 km overlain on a monochrome shaded relief map of the topography.

This image shows especially strong Martian magnetic fields in the southern highlands near the Terra Cimmeria and Terra Sirenum regions, centered around 180 degrees longitude from the equator to the pole. It is where magnetic stripes possibly resulting from crustal movement are most prominent. The bands are oriented approximately east - west and are about 100 miles wide and 600 miles long, although the longest band stretches more than 1200 miles.

The false blue and red colors represent invisible magnetic fields in the Martian crust that point in opposite directions. The magnetic fields appear to be organized in bands, with adjacent bands pointing in opposite directions, giving these stripes a striking similarity to patterns seen in the Earth's crust at the mid-oceanic ridges.

These data were compiled by the MGS Magnetometer Team led by Mario Acuna at the Goddard Space Flight Center in Greenbelt, MD.

2001-01-01

93

Origin of primordial magnetic fields  

SciTech Connect

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

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

2008-02-15

94

Magnetic field tomography, helical magnetic fields and Faraday depolarization  

NASA Astrophysics Data System (ADS)

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

Horellou, C.; Fletcher, A.

2014-07-01

95

Magnetic fields around black holes  

NASA Astrophysics Data System (ADS)

Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our Newtonian results are excellent approximations for slowly spinning black holes. We proceed to address the issue of the spin dependence of the Blandford & Znajek power. The result we choose to highlight is our finding that given the validity of our assumption for the dynamical behavior of the so-called plunge region in black hole accretors, rotating black holes produce maximum Poynting flux via the Blandford & Znajek process for a black hole spin parameter of about a [approximate] 0.8. This is contrary to the conventional claim that the maximum electromagnetic flux is achieved for highest black hole spin.

Garofalo, David A. G.

96

EXPLORER 10 MAGNETIC FIELD MEASUREMENTS  

Microsoft Academic Search

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

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

1963-01-01

97

Crystal field and magnetic properties  

NASA Technical Reports Server (NTRS)

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

Flood, D. J.

1977-01-01

98

Transverse Magnetic Field Propellant Isolator  

NASA Technical Reports Server (NTRS)

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

Foster, John E.

2000-01-01

99

Diffusion of magnetic field via turbulent reconnection  

Microsoft Academic Search

The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence is reassuring that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as

Reinaldo Santos de Lima; Alexander Lazarian; Elisabete M. de Gouveia Dal Pino; Jungyeon Cho

2010-01-01

100

Separation of magnetic field lines  

SciTech Connect

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

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

2012-11-15

101

Magnetic fields in the sun  

NASA Technical Reports Server (NTRS)

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

Mullan, D. J.

1974-01-01

102

Magnetic Field Line Simulation Using a Microcomputer.  

ERIC Educational Resources Information Center

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

Kirkup, L.

1986-01-01

103

The HMI Magnetic Field Pipeline  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

2009-05-01

104

Large magnetic field instabilities induced by magnetic dipole transitions  

Microsoft Academic Search

We present a new mechanism that will limit very high magnetic fields which have been conjectured to exist in connection with some astrophysical phenomena. Low lying strongly interacting particles and resonances mixing with each other via magnetic dipole QED couplings force a vacuum instability for large external magnetic fields. These mixings limit fields to a few GeV2.

Myron Bander; H. R. Rubinstein

1992-01-01

105

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

Microsoft Academic Search

This article describes both the setup and the use of a system for magnetic resonance imaging (MRI) in the Earth's magnetic field. Phase instability caused by temporal fluctuations of Earth's field can be successfully improved by using a reference signal from a separate Earth's field nuclear magnetic resonance (NMR) spectrometer\\/magnetometer. In imaging, it is important to correctly determine the phase

Ales Mohoric; Gorazd Planinsic; Miha Kos; Andrej Duh; Janez Stepisnik

2004-01-01

106

The Giotto magnetic field investigation  

Microsoft Academic Search

The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28\\/sec during close encounter,

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

1983-01-01

107

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

E-print Network

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

Fornberg, Bengt

108

Development Trends in High Field Magnet Technology  

Microsoft Academic Search

The production of high magnetic fields using low temperature superconductors (LTS) has become common place. However, large magnet sizes and associated high cooling costs have often precluded the full utilization of these research capabilities. Recent advances in internal Sn superconductors and cryogen free technology have opened up a new era in superconducting magnet development. Ultra-compact, laboratory sized magnets producing fields

R. Harrison; R. Bateman; J. Brown; F. Domptail; C. M. Friend; P. Ghoshal; C. King; A. Van der Linden; Z. Melhem; P. Noonan; A. Twin; M. Field; S. Hong; J. Parrell; Y. Zhang

2008-01-01

109

Electromagnetic field of a charge intersecting a cold plasma boundary in a waveguide.  

PubMed

We analyze the electromagnetic field of a charge crossing a boundary between a vacuum and cold plasma in a waveguide. We obtain exact expressions for the field components and the spectral density of the transition radiation. With the steepest descent technique, we investigate the field components. We show that the electromagnetic field has a different structure in a vacuum than in cold plasma. We also develop an algorithm for the computation of the field based on a certain transformation of the integration path. The behavior of the field depending on distance and time and the spectral density depending on frequency are explored for different charge velocities. Some important physical effects are noted. A considerable increase and concentration of the field near the wave front in the plasma is observed for the case of ultrarelativistic particles. In the plasma, the mode envelopes and spectral density show zero points when the charge velocity is within certain limits. PMID:21797492

Alekhina, Tatiana Yu; Tyukhtin, Andrey V

2011-06-01

110

Electromagnetic field of a charge intersecting a cold plasma boundary in a waveguide  

SciTech Connect

We analyze the electromagnetic field of a charge crossing a boundary between a vacuum and cold plasma in a waveguide. We obtain exact expressions for the field components and the spectral density of the transition radiation. With the steepest descent technique, we investigate the field components. We show that the electromagnetic field has a different structure in a vacuum than in cold plasma. We also develop an algorithm for the computation of the field based on a certain transformation of the integration path. The behavior of the field depending on distance and time and the spectral density depending on frequency are explored for different charge velocities. Some important physical effects are noted. A considerable increase and concentration of the field near the wave front in the plasma is observed for the case of ultrarelativistic particles. In the plasma, the mode envelopes and spectral density show zero points when the charge velocity is within certain limits.

Alekhina, Tatiana Yu.; Tyukhtin, Andrey V. [Radiophysics Department of St. Petersburg University, 1 Ulyanovskaya, St. Petersburg 198504 (Russian Federation)

2011-06-15

111

Comparing Magnetic Fields on Earth and Mars  

NASA Video Gallery

This animation compares the magnetic fields on Earth and Mars. The Earth has a large-scale planetary magnetic field that can protect it from space weather and other hazards. Mars, on the other hand...

112

Measurements of Solar Vector Magnetic Fields  

NASA Technical Reports Server (NTRS)

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

Hagyard, M. J. (editor)

1985-01-01

113

Plasma stability in a dipole magnetic field  

E-print Network

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

Simakov, Andrei N., 1974-

2001-01-01

114

What Are Electric and Magnetic Fields? (EMF)  

MedlinePLUS

What are Electric and Magnetic Fields? (EMF) Electric and Magnetic Fields Electricity is an essential part of our lives. Electricity powers all sorts of things around us, from computers to refrigerators ...

115

Primordial magnetic field limits from cosmological data  

SciTech Connect

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

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

2010-10-15

116

Magnetic-Field Processing of Industrial Effluents  

Microsoft Academic Search

the field acts on pollutants in the colloidal state; and the field influences the structure of the water. Magnetic treatment is simple, safe, and very inexpensive, but a patent search under the topic Magnetic treatment of water and aqueous solutions has shown that the existing devices and methods for using magnetic fields to process effluents containing heavy-metal ions

V. P. Malkin

2002-01-01

117

Magnetic field navigation in an indoor environment  

Microsoft Academic Search

This paper describes a method that has been developed to aid an inertial navigation system when GNSS signals are not available, by taking advantage of the uniqueness of magnetic field variations. Most indoor environments have many different features (ferrous structural materials or contents, electrical currents, etc.) which perturb the Earths natural magnetic field. The variations in the magnetic field in

William Storms; Jeremiah Shockley; John Raquet

2010-01-01

118

CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION  

E-print Network

Chapter 5 CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION Stephen M. White This article reviews the use of gyroresonance emission at radio wavelengths to measure coronal magnetic fields probes of the magnetic field strength above active regions, and this unique capability is one

White, Stephen

119

Appendix E: Software MEASURING CONSTANT MAGNETIC FIELD  

E-print Network

E - 1 Appendix E: Software MEASURING CONSTANT MAGNETIC FIELD (THE HALL PROBE APPLICATION) Basics yourself with the equipment. The software package that works in tandem with your magnetic field sensor is written in LabVIEWTM. It allows you to measure and record magnetic field strength as a function

Minnesota, University of

120

Quenching of flames by magnetic fields (abstract)  

Microsoft Academic Search

The effects of magnetic fields on combustion of alcohol with the aid of platinum catalysis have been studied to simulate in part the oxidation of organic matter in the living body, and it has been found that the combustion reactions are influenced by magnetic fields. It has also been observed that candle flames are pressed down by magnetic fields of

S. Ueno

1988-01-01

121

Applied Magnetic Field Enhances Arc Vapor Deposition  

NASA Technical Reports Server (NTRS)

Applied magnetic field enhances performance of vaporization part of arc vapor deposition apparatus. When no magnetic field applied by external means, arc wonders semirandomly over cathode, with net motion toward electrical feedthrough. When magnetic field applied arc moves circumferentially around cathode, and downward motion suppressed.

Miller, T. A.; Loutfy, R. O.; Withers, J. C.

1993-01-01

122

Magnetic field and radiative transfer modelling of a quiescent prominence  

NASA Astrophysics Data System (ADS)

Aims: The aim of this work is to analyse the multi-instrument observations of the June 22, 2010 prominence to study its structure in detail, including the prominence-corona transition region and the dark bubble located below the prominence body. Methods: We combined results of the 3D magnetic field modelling with 2D prominence fine structure radiative transfer models to fully exploit the available observations. Results: The 3D linear force-free field model with the unsheared bipole reproduces the morphology of the analysed prominence reasonably well, thus providing useful information about its magnetic field configuration and the location of the magnetic dips. The 2D models of the prominence fine structures provide a good representation of the local plasma configuration in the region dominated by the quasi-vertical threads. However, the low observed Lyman-? central intensities and the morphology of the analysed prominence suggest that its upper central part is not directly illuminated from the solar surface. Conclusions: This multi-disciplinary prominence study allows us to argue that a large part of the prominence-corona transition region plasma can be located inside the magnetic dips in small-scale features that surround the cool prominence material located in the dip centre. We also argue that the dark prominence bubbles can be formed because of perturbations of the prominence magnetic field by parasitic bipoles, causing them to be devoid of the magnetic dips. Magnetic dips, however, form thin layers that surround these bubbles, which might explain the occurrence of the cool prominence material in the lines of sight intersecting the prominence bubbles. Movie and Appendix A are available in electronic form at http://www.aanda.org

Gunr, S.; Schwartz, P.; Dudk, J.; Schmieder, B.; Heinzel, P.; Jur?k, J.

2014-07-01

123

Effects of magnetic fields on fibrinolysis  

NASA Astrophysics Data System (ADS)

In this study, we investigated the possible effects of magnetic fields on the fibrinolytic process. Fibrin dissolution was observed and the fibrinolytic activities were evaluated. First, fibrinolytic processes in magnetic fields were investigated by the fibrin plate method. We gathered solutions from the dissolved fibrin, and measured mean levels of fibrin degradation products (FDPs) in solutions. Mean levels of FDPs exposed to 8 T magnetic fields were higher than those not exposed to fields. Second, we carried out an experiment to understand how fibrin oriented in a magnetic field dissolves. FDPs in solutions of dissolved fibrins in fibrin plates were assayed. The result was that fibrin gels formed in a magnetic field at 8 T were more soluble than those not formed in a magnetic field. A model based on the diamagnetic properties of macromolecules was explained, and changes of protein concentrations in a solution in gradient magnetic fields were predicted.

Iwasaka, M.; Ueno, S.; Tsuda, H.

1994-05-01

124

Magnetic monopole and the nature of the static magnetic field  

E-print Network

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

Xiuqing Huang

2008-12-10

125

Heliospheric magnetic fields and plasmas  

NASA Technical Reports Server (NTRS)

A survey of the existing literature on heliospheric physics, covering the period 1972-1982, is presented. Attention is given to observations and theories germane to the examination of the heliosphere as a large-scale astrophysical system that is part of the earth's environment. The literature includes data and models for magnetic sectors and the large-scale magnetic field, the large-scale plasma structure, and models and observed variations in the solar wind. Consideration is also devoted to the transient and corotating streams and shocks, the composition of the solar wind, and to MHD turbulence, waves, and discontinuities. More intensive investigations of the region near 1 AU are recommended, particularly to characterize the coronal source of the solar wind. The solar polar mission will be the first to provide radial measurements for comparisons with previous exclusively ecliptic measurements of solar activities.

Burlaga, L. F.

1983-01-01

126

The Giotto magnetic field investigation  

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

127

Magnetic Helicity and Large Scale Magnetic Fields: A Primer  

E-print Network

Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. H...

Blackman, Eric G

2014-01-01

128

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

E-print Network

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

129

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

E-print Network

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

Shull, Kenneth R.

130

The magnetic field over the Southern African continent: from core to crustal magnetic fields  

Microsoft Academic Search

Secular magnetic field evolutions do not proceed in a regular way all over the Earth. In some regions like Southern Africa, the field has been changing more rapidly than elsewhere. During the last five decades, the Earth's magnetic field has been represented in spherical harmonics from a series of measurements that were generally obtained at magnetic field observatories. Unfortunately, magnetic

Erwan Thbault; Pieter Kotze; Arnaud Chulliat; Fotini Vervelidou

2010-01-01

131

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

DOEpatents

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

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

2000-12-19

132

Magnetic fluid flow phenomena in DC and rotating magnetic fields  

E-print Network

An investigation of magnetic fluid experiments and analysis is presented in three parts: a study of magnetic field induced torques in magnetorheological fluids, a characterization and quantitative measurement of properties ...

Rhodes, Scott E. (Scott Edward), 1981-

2004-01-01

133

Magnetic field effects on microwave absorbing materials  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

134

Field Effect Flow Control in a Polymer T-Intersection Microfluidic Network  

NASA Technical Reports Server (NTRS)

We present a study of induced pressure pumping in a polymer microchannel due to differential electroosmotic flow @OF) rates via field-effect flow control (FEFC). The experimental results demonstrate that the induced pressure pumping is dependent on the distance of the FEFC gate from the cathodic gate. A proposed flow model based on a linearly-decaying zeta potential profile is found to successfully predict experimental trends.

Sniadecki, Nathan J.; Chang, Richard; Beamesderfer, Mike; Lee, Cheng S.; DeVoe, Don L.

2003-01-01

135

Problems with magnetic field measurements on spacecrafts  

Microsoft Academic Search

The paper summarizes the difficulties and possible solutions to design and evaluate accurate vector magnetic field measurements on spacecrafts in the interplanetary magnetic field. Problems are discussed like calibration, boom mounted sensors and misalignment angles determination in flight. The application of a detailed magnetic cleanliness program as an example the comet Halley-Giotto spacecraft is demonstrated in detail. The use of

Gnter Musmann

1988-01-01

136

Neutrinos with Mixing in Twisting Magnetic Fields  

E-print Network

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

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

1993-01-06

137

Discovery of magnetic fields in CPNs  

E-print Network

For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our sample we found kilogauss magnetic fields, in NGC 1360 and LSS1362 with very high significance, while in Abell36 and EGB5 the existence of a magnetic field is probable but with less certainty. This discovery supports the hypothesis that the non-spherical symmetry of most planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery rate demands mechanisms to prevent full conservation of magnetic flux during the transition to white dwarfs.

S. Jordan; K. Werner; S. J. O'Toole

2004-10-21

138

Current Transport and Onset-Related Phenomena in an MPD Thruster Modified by Applied Magnetic Fields  

NASA Astrophysics Data System (ADS)

This work investigated the effects of tailored, externally-applied magnetic fields on current transport and near-anode processes in the plasma discharge of a magnetoplasmadynamic thruster (MPDT). Electrical and plasma diagnostics were used to determine whether applied magnetic fields could mitigate the effects of the "onset" phenomena, including large-amplitude terminal voltage fluctuations and high anode fall voltages associated with unstable operation and anode erosion. A new MPDT was developed and operated with quasi-steady 1 ms pulses from 36 kW to 3.3 MW with argon propellant. Three magnetic configurations studied included self-field operation (without external electromagnets) and two applied poloidal magnetic fields. One configuration used magnetic field lines tangential to the anode lip (and intersecting the anode further upstream) and the other created a magnetic cusp intersecting the anode downstream. The influence of the applied fields on the discharge current streamlines, current densities, and key plasma properties (electron temperature, number density, and plasma potential) was studied. Key findings included that the current pattern and current densities redistributed to follow the applied magnetic field lines. Also, the anode fall voltage was substantially reduced with both applied fields over a large range of currents (and eliminated at 8 kA). These results occurred because applied magnetic field lines intersecting the anode provided a high conductivity path and reduced the local electric field required to sustain the radial current densities. The applied fields reduced the amplitude and frequency of the terminal voltage fluctuations (up to 49%) over a broad range of currents and also decreased transients in the ion saturation current, which suggest reduction of current filamentation and surface-eroding anode spots. Additionally, the cusp field reduced mean terminal voltages over the entire range of discharge currents (up to 31%), and the tangential field lowered terminal voltages below 10.7 kA. These significant reductions in onset-related behaviors should lead to improved thruster lifetime and increased efficiency. These results suggest a distinctive and more effective approach to influencing the near-anode phenomena and mitigating the effects of onset with appropriately designed applied magnetic fields that differ from those used in the vast majority of conventional, so-called "applied-field MPD thrusters."

Moeller, Robert Carlos

139

Unique topological characterization of braided magnetic fields  

SciTech Connect

We introduce a topological flux function to quantify the topology of magnetic braids: non-zero, line-tied magnetic fields whose field lines all connect between two boundaries. This scalar function is an ideal invariant defined on a cross-section of the magnetic field, and measures the average poloidal magnetic flux around any given field line, or the average pairwise crossing number between a given field line and all others. Moreover, its integral over the cross-section yields the relative magnetic helicity. Using the fact that the flux function is also an action in the Hamiltonian formulation of the field line equations, we prove that it uniquely characterizes the field line mapping and hence the magnetic topology.

Yeates, A. R. [Department of Mathematical Sciences, Durham University, Durham DH1 3LE (United Kingdom); Hornig, G. [Division of Mathematics, University of Dundee, Dundee DD1 4HN (United Kingdom)

2013-01-15

140

Bipolar pulse field for magnetic refrigeration  

DOEpatents

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

Lubell, M.S.

1994-10-25

141

Advances in Remote Sensing of Magnetic Fields  

NASA Astrophysics Data System (ADS)

In sharp contrast to stellar magnetic fields, geomagnetic fields have never been remotely sensed. If geomagnetic fields could be measured remotely at the nanotesla (nT) level or better, our understanding of the processes that produce these fields would advance markedly. Unlike characteristics such as topography and temperature, measurements of the magnetic field are determined almost exclusively in situ. The inability to remotely sense these fields has hindered their utility. The Remote Atmospheric Magnetics Workshop highlighted advances in this frontier area, focusing on lab- and field-based studies.

Purucker, Michael

2014-09-01

142

Franck-Hertz experiment in magnetic field  

E-print Network

The paper studies the impact of applied magnetic field on the inelastic collisions of electrons with argon atoms. In the electron-argon Franck-Hertz experiment, the influence of applied magnetic field emerges complicated features, and is equivalent to that of the temperature. In case the accelerating electric intensity becomes strong enough, enlarging magnetic flux density will be equivalent to the increasing of oven temperature. When the accelerating electric intensity is very weak and the applied magnetic field occupies a dominant position, enhancing magnetic flux density is identical with the decreasing of oven temperature. And the non-uniform distribution of applied magnetic field has an influence on the inelastic collision as well. The study claims that the influence of magnetic field variation is equivalent to that of temperature variety, and that it leads the electron energy to transfer obviously in the experiment.

Ying Weng; Zi-Hua Weng

2010-10-07

143

Magnetic Fields and Rotations of Protostars  

E-print Network

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

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

2007-02-07

144

Measuring T Tauri star magnetic fields  

Microsoft Academic Search

Stellar magnetic fields including a strong dipole component are believed to play a critical role in the early evolution of newly formed stars and their circumstellar accretion disks. It is currently believed that the stellar magnetic field truncates the accretion disk several stellar radii above the star. This action forces accreting material to flow along the field lines and accrete

Christopher M. Johns-Krull

2009-01-01

145

DC-based magnetic field controller  

DOEpatents

A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

1994-01-01

146

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

147

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of 3 identical satellites. The Mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

Plank, Gernot; Haagmans, Roger; Floberghagen, Rune; Menard, Yvon

2013-04-01

148

Comparing magnetic field extrapolations with measurements of magnetic loops  

E-print Network

We compare magnetic field extrapolations from a photospheric magnetogram with the observationally inferred structure of magnetic loops in a newly developed active region. This is the first time that the reconstructed 3D-topology of the magnetic field is available to test the extrapolations. We compare the observations with potential fields, linear force-free fields and non-linear force-free fields. This comparison reveals that a potential field extrapolation is not suitable for a reconstruction of the magnetic field in this young, developing active region. The inclusion of field-line-parallel electric currents, the so called force-free approach, gives much better results. Furthermore, a non-linear force-free computation reproduces the observations better than the linear force-free approximation, although no free parameters are available in the former case.

T. Wiegelmann; A. Lagg; S. K. Solanki; B. Inhester; J. Woch

2008-01-29

149

Magnetic Fields in Clusters of Galaxies  

E-print Network

A brief overview about our knowledge on galaxy cluster magnetic fields is provided. Emphasize is given to the mutual dependence of our knowledge on relativistic particles in galaxy clusters and the magnetic field strength. Furthermore, we describe efforts to measure magnetic field strengths, characteristic length-scales, and power-spectra with reliable accuracy. An interpretation of these results in terms of non-helical dynamo theory is given. If this interpretation turns out to be correct, the understanding of cluster magnetic fields is directly connected to our understanding of intra-cluster turbulence.

Torsten A. Ensslin; Corina Vogt; Christoph Pfrommer

2005-01-17

150

Ferroelectric Cathodes in Transverse Magnetic Fields  

SciTech Connect

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

Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

2002-07-29

151

Statistics of magnetic fields on OBA stars  

NASA Astrophysics Data System (ADS)

Starting from recent measurements, we studied the statistical properties of the magnetic fields of OBA stars. As one of the statistically significant characteristics of the magnetic field we use the average effective magnetic field of the star, < B>. We then investigated the distribution function f() of the magnetic fields of OBA stars. This function has a power-law dependence on , with an index of 2-3 and a fast decrease for ? 300 G for B-A stars and ? 80 G for O stars.

Kholtygin, A. F.; Hubrig, S.; Drake, N. A.; Sudnik, N. P.; Dushin, V. V.

2014-11-01

152

Magnetic monopole field exposed by electrons  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

153

Concentrator of magnetic field of light  

NASA Astrophysics Data System (ADS)

In the recent decade metamaterials with magnetic permeability different than unity and unusual response to the magnetic field of incident light have been intensively explored. Existence of magnetic artificial materials created an interest in a scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of those metamaterials. We present a method of measuring magnetic responses of such elementary cells within a wide range of optical frequencies with single probes of two types. The first type probe is made of a tapered silica fiber with radial metal stripes separated by equidistant slits of constant angular width. The second type probe is similar to metal coated, corrugated, tapered fiber apertured SNOM probe, but in this case corrugations are radially oriented. Both types of probes have internal illumination with azimuthally polarized light. In the near-field they concentrate into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one.

Wrbel, Piotr; Stefaniuk, Tomasz; Antosiewicz, Tomasz J.; Szoplik, Tomasz

2012-05-01

154

Magnetic field screening effect in electroweak model  

E-print Network

It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of that phenomenon is conditioned by features of the electro-weak interaction, namely, there is mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that corresponding magnetic bound state exists in the electroweak theory and can be detected in experiment.

Bakry, A; Zhang, P M; Zou, L P

2014-01-01

155

Numerical analysis of magnetic field in superconducting magnetic energy storage  

SciTech Connect

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

Kanamaru, Y. (Kanazawa Inst. of Technology, 7-1 Ohgigaoka, Nonoichi, Ishikawa 921 (JP)); Amemiya, Y. (Chiba Inst. of Tech., Narashino (Japan))

1991-09-01

156

Reducing Field Distortion in Magnetic Resonance Imaging  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

157

Electro-magnetically induced transparency in a static magnetic field  

NASA Astrophysics Data System (ADS)

We investigate both theoretically and experimentally the electro- magnetically induced transparency (EIT) phenomenon of atomic 87Rb at the room temperature with a static magnetic field lifting the degeneracy of all three involved hyperfine levels. Two collinearly propagating and linearly polarized laser fields (a probe field and a coupling field) are used to couple one hyperfine level (the upper level) of the 5P 1/2 state to two hyperfine levels (the lower levels) of the 5S 1/2 state, respectively. In the case of zero magnetic fields, we observed a deep EIT window with the contrast of about 66%. Here, the EIT window width is limited by both the spontaneous decay rate of the upper level and the coupling field intensity. When a magnetic field parallel to both laser beams is applied, the EIT window is split into three much narrower sub-windows with contrasts of about 32%. If the magnetic field is perpendicular to the laser beams, however, the EIT window is split into four much narrower sub-windows whose contrasts are 32% or 16%. This is because the decomposition of the linearly polarized optical fields strongly depends on the orientation of the used magnetic field. The underlying physics is that, in the limit of a weak probe field, an ideal degenerate three-level system can be split into three or four sets of independent three-level systems by a magnetic field due to the lifting of magnetic sublevels of the involved hyperfine levels. In this paper the absorption spectra corresponding to different magnetic field directions are clearly shown and compared. And a straightforward but effective theoretical method for analyzing the experimental results is put forward. Our theoretical calculations are in good agreement with the experimental results.

Wei, Xiao-Gang; Gao, Jin-Yue; Wu, Jin-Hui; Sun, Gui-Xia; Wang, Hai-Hua; Kang, Zhi-Hui; Shao, Zhuang; Jiang, Yun

2006-02-01

158

Destruction of magnetic surfaces by magnetic field irregularities: Part II  

Microsoft Academic Search

The present work is a continuation of the paper by Rosenbluth et al. (Nucl. Fusion 6 (1966) 297) and concerns the investigation of problems associated with the condition for the existence of magnetic surfaces in closed systems of the stellarator type. The unperturbed geometry of the magnetic field is produced by a straight helical field. Exact equations for the motion

N. N. Filonenko; R. Z. Sagdeev; G. M. Zaslavskii

1967-01-01

159

Magnetic Field Line Topology of the Scrape-Off Layer in the Compact Stellarator NCSX  

NASA Astrophysics Data System (ADS)

The magnetic topology of the plasma boundary of the proposed compact stellarator NCSX is investigated using the MFBE[1] and VMEC2000[2] codes. The VMEC code provides a free boundary equilibrium and the magnetics from external coils and bootstrap plasma currents inside the last closed magnetic surface (LCMS). The MFBE code uses these results to calculate the magnetic fields of these finite beta equilibria outside the LCMS in a form suitable for line tracing. The Poincar plots of field lines started outside the LCMS indicate preservation of initial radial ordering of field lines up to intersections with vacuum vessel and plasma facing components. A large flux expansion of field lines is observed between the midplane and tips of the banana shaped cross-section, due to the presence of a nearby poloidal field null used to create the banana shape. TRIM coils used to heal islands just within the LCMS appear to reduce stochasticity just outside the LCMS as well as enhance an island structure outside the LCMS. Field lines are observed to move in and out radially as they are followed toroidally. Power and particle control design based on these observations include the limiting structure geometry and baffles designed to intersect islands outside the LCMS. [1] E.Strumberger, Nuclear Fusion 37 1997 19. [2] S.Hirshman, Comp. Phys. Commun. 43 1986 143.

Grossman, Arthur; Mioduszewski, Peter; Fenstermacher, Max; Koniges, Alice; Rognlien, Tom

2001-10-01

160

Cosmic Magnetic Fields (IAU S259)  

NASA Astrophysics Data System (ADS)

Preface K. G. Strassmeier, A. G. Kosovichev and J. E. Beckman; Organising committee; Conference photograph; Conference participants; Session 1. Interstellar magnetic fields, star-forming regions and the Death Valley Takahiro Kudoh and Elisabeta de Gouveia Dal Pino; Session 2. Multi-scale magnetic fields of the Sun; their generation in the interior, and magnetic energy release Nigel O. Weiss; Session 3. Planetary magnetic fields and the formation and evolution of planetary systems and planets; exoplanets Karl-Heinz Glassmeier; Session 4. Stellar magnetic fields: cool and hot stars Swetlana Hubrig; Session 5. From stars to galaxies and the intergalactic space Dimitry Sokoloff and Bryan Gaensler; Session 6. Advances in methods and instrumentation for measuring magnetic fields across all wavelengths and targets Tom Landecker and Klaus G. Strassmeier; Author index; Object index; Subject index.

Strassmeier, Klaus G.; Kosovichev, Alexander G.; Beckman, John E.

2009-06-01

161

SIMULATING MAGNETIC FIELDS IN THE ANTENNAE GALAXIES  

SciTech Connect

We present self-consistent high-resolution simulations of NGC 4038/4039 (the 'Antennae galaxies') including star formation, supernova feedback, and magnetic fields performed with the N-body/smoothed particle hydrodynamic (SPH) code GADGET, in which magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 10{sup -9} to 10{sup -4} G. At the time of the best match with the central region of the Antennae system, the magnetic field has been amplified by compression and shear flows to an equilibrium field value of {approx}10 {mu}G, independent of the initial seed field. These simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of regular magnetic fields between the cores and at the root of the southern tidal arm develop naturally in our simulations. This indicates that the simulations are capable of realistically following the evolution of the magnetic fields in a highly nonlinear environment. We also discuss the relevance of the amplification effect for present-day magnetic fields in the context of hierarchical structure formation.

Kotarba, H.; Karl, S. J.; Naab, T.; Johansson, P. H.; Lesch, H. [University Observatory Munich, Scheinerstr. 1, D-81679 Munich (Germany); Dolag, K.; Stasyszyn, F. A., E-mail: kotarba@usm.lmu.d [Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)

2010-06-20

162

Atoms in Crossed Electric and Magnetic Fields  

NASA Astrophysics Data System (ADS)

In this dissertation, extensive experimental and theoretical work pertaining to three interesting aspects of the interaction of atoms with crossed electric and magnetic fields is presented. The first experiment discussed deals with the effects of weak crossed fields on sodium atoms. A fluorescence spectrum of laser excited sodium n = 11 states in an electric field of 2560 V/cm perpendicular to a magnetic field of 4.4 kG is presented, along with a comparison to theory. The data show the important effects of m-mixing and residual degeneracies which remain in the crossed fields. The next topic presented is the theoretical prediction of novel resonances, termed "quasi-Penning resonances," corresponding to electron states localized away from the nucleus at the Stark saddlepoint in strong crossed electric and magnetic fields. The stability and possibility for observation of these resonances is explored. Finally, extensive experimental maps of data are presented which compare laser induced ionization spectra of sodium atoms in crossed electric and magnetic fields to spectra in an electric field atone. The experiment explores the energy region of the electric field saddlepoint, where quasi-Penning resonances are predicted to occur. The magnetic field is too weak for the observation of these resonances, but the experiment provides important groundwork for the understanding of future experiments in strong crossed fields. The magnetic field is seen to cause splitting of some transitions due to the interaction of the electron spin with the magnetic field. Also, magnetic field induced state mixing causes a redistribution of oscillator strengths leading to changes in peak heights and auto-ionizing line widths. On the whole, however, the effect of the weak crossed magnetic field on the sodium Stark spectra remains small.

Korevaar, Eric John

1987-09-01

163

Calculation of magnetic fields for engineering devices  

Microsoft Academic Search

This paper deals with the methodology of magnet technology and its application to various engineering devices. Magnet technology has experienced a rapid growth in the past few years as a result of the advances made in superconductivity, numerical methods and computational techniques. Specifically, this paper concerns itself with: (a) Mathematical models for solving magnetic field problems; (b) The applicability, usefulness,

John S. Colonias

1976-01-01

164

The Evolution of the Earth's Magnetic Field.  

ERIC Educational Resources Information Center

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

Bloxham, Jeremy; Gubbins, David

1989-01-01

165

Coronal magnetic fields and the solar wind  

NASA Technical Reports Server (NTRS)

Current information is presented on coronal magnetic fields as they bear on problems of the solar wind. Both steady state fields and coronal transient events are considered. A brief critique is given of the methods of calculating coronal magnetic fields including the potential (current free) models, exact solutions for the solar wind and field interaction, and source surface models. These solutions are compared with the meager quantitative observations which are available at this time. Qualitative comparisons between the shapes of calculated magnetic field lines and the forms visible in the solar corona at several recent eclipses are displayed. These suggest that: (1) coronal streamers develop above extended magnetic arcades which connect unipolar regions of opposite polarity; and (2) loops, arches, and rays in the corona correspond to preferentially filled magnetic tubes in the approximately potential field.

Newkirk, G., Jr.

1972-01-01

166

Magnetic field decay in model SSC dipoles  

SciTech Connect

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

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

1988-08-01

167

Protecting SQUID metamaterials against stray magnetic fields  

NASA Astrophysics Data System (ADS)

Using superconducting quantum interference devices (SQUIDs) as the basic, low-loss elements of thin-film metamaterials has one main advantage: their resonance frequency is easily tunable by applying a weak magnetic field. The downside, however, is a strong sensitivity to stray and inhomogeneous magnetic fields. In this work, we demonstrate that even small magnetic fields from electronic components destroy the collective, resonant behaviour of the SQUID metamaterial. We also show how the effect of these fields can be minimized. As a first step, magnetic shielding decreases any initially present fields, including the earths magnetic field. However, further measures such as improvements in the sample geometry have to be taken to avoid the trapping of Abrikosov vortices.

Butz, S.; Jung, P.; Filippenko, L. V.; Koshelets, V. P.; Ustinov, A. V.

2013-09-01

168

Investigation of radial electric field in the edge region and magnetic field structure in the Large Helical Device  

NASA Astrophysics Data System (ADS)

In the Large Helical Device experiments, a significant pressure gradient is observed in the edge region where the three-dimensional magnetohydrodynamics equilibrium analysis predicts the stochastization of magnetic field lines. Therefore, experimental investigation of this edge plasma behavior is attracting much interest to identify either the plasma response to stochastic magnetic fields or the topological change of magnetic fields due to the plasma. In this study, we have investigated the relation of the stochastization of magnetic field lines to the radial electric field, Er. When magnetic field lines become stochastic or open and connected to the vessel, electrons are lost along these field lines while ions are trapped. Then, a strong Er shear from negative to positive appears at the boundary. Two magnetic configurations with different widths of the stochastic layer in the vacuum are studied for low-? discharges. It has been found that the position of a strong Er shear appears outside of the last closed flux surface. When comparing the vacuum magnetic field, the positions of strong Er shear are observed in the edge of the stochastic layer. In the stochastic region, the scatter of stochastic field lines is studied. The position of a strong Er shear appears in the region where the outward scatter of the field lines increases. In that region, stochastic field lines intersect the regions with long and short connection lengths. Although the connection length is longer than the electron mean free path, the scatter of stochastic field lines with short connection lengths appear in the regions with positive Er. These results are compared with moderate-? discharges, where a large plasma response is expected. The prediction of the vacuum magnetic field qualitatively agree with the experimental observations but quantitative differences are found.

Suzuki, Y.; Ida, K.; Kamiya, K.; Yoshinuma, M.; Tsuchiya, H.; Inagaki, S.; Sakakibara, S.; Watanabe, K. Y.; Narushima, Y.; Ohdachi, S.; Yamada, I.; Yasuhara, R.; Tanaka, K.; Akiyama, T.; Yamada, H.; the LHD Experiment Group

2013-12-01

169

Graphene Nanoribbon in Sharply Localized Magnetic Fields  

E-print Network

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

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

2011-03-21

170

Extended Magnetization of Superconducting Pellets in Highly Inhomogeneous Magnetic Field  

NASA Astrophysics Data System (ADS)

The magnetization of superconducting pellets is a worth point in the development of trapped flux superconducting motors. Experimental and simulated data have been reported extensively according to the framework of one or several pulses of a homogeneous magnetizing field applied to a pellet or a set of pellets. In case of cylindrical rotors of low power motors with radial excitation, however, the use of the copper coils to produce the starting magnetization of the pellets produces a highly inhomogeneous magnetic field which cannot be reduced to a 2D standard model. In this work we present an analysis of the magnetization of the superconducting cylindrical rotor of a small motor by using a commercial FEM program, being the rotor magnetized by the working copper coils of the motor. The aim of the study is a report of the magnetization obtained and theheat generated in the HTSC pellets.

Maynou, R.; Lpez, J.; Granados, X.; Torres, R.; Bosch, R.

171

The Physics of Attraction and Repulsion: Magnetism and Magnetic Fields  

NASA Astrophysics Data System (ADS)

The development of new materials with improved magnetic properties completely changed the modern world in the past decades. Recent progress is predominantly due to a better understanding of magnetism that has gone far beyond compass needles rotating in a magnetic field and bar magnets attracting or repelling each other. New magnetic materials are used to build smaller and smaller read/write heads and hard disks with increased storage capacity, developments that are responsible the revolution in the computer industry. Another example is the field of magnetic levitation that became feasible for commercial applications with the discovery of new superconducting materials, and a prototype train is under development in Japan. In medicine, the development of magnetic resonance imaging (MRI) provides an alternative to other (destructive) radiation techniques.

Nakotte, Heinz

2001-11-01

172

High concentration ferronematics in low magnetic fields  

E-print Network

We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field $B_{bias}$, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that $B_{bias}$ is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

T. Tth-Katona; P. Salamon; N. ber; N. Tomaovi?ov; Z. Mitrov; P. Kop?ansk

2014-09-05

173

High concentration ferronematics in low magnetic fields  

NASA Astrophysics Data System (ADS)

We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field Bbias, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that Bbias is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

Tth-Katona, T.; Salamon, P.; ber, N.; Tomaovi?ov, N.; Mitrov, Z.; Kop?ansk, P.

2014-12-01

174

Comparison of the mean photospheric magnetic field and the interplanetary magnetic field  

Microsoft Academic Search

The mean photospheric magnetic field of the sun seen as a star has been compared with the interplanetary magnetic field observed with spacecraft near the earth. Each change in polarity of the mean solar field is followed about 4 1\\/2 days later by a change in polarity of the interplanetary field (sector boundary). The scaling of the field magnitude from

A. Severny; J. M. Wilcox; P. H. Scherrer; D. S. Colburn

1970-01-01

175

Correlation properties of magnetosheath magnetic field fluctuations  

Microsoft Academic Search

The magnetosheath is characterized by a variety of low-frequency fluctuations, but their features and sources are different. Taking advantage of multipoint magnetic field measurements of the Cluster spacecraft, we present a statistical study to reveal properties of waves. We compute cross-correlation coefficients of magnetic field strengths as measured by pairs of the Cluster spacecraft and determine the correlation length of

O. Gutynska; J. afrnkov; Z. N?me?ek

2009-01-01

176

Magnetic fields, branes, and noncommutative geometry  

Microsoft Academic Search

We construct a simple physical model of a particle moving on the infinite noncommutative 2-plane. The model consists of a pair of opposite charges moving in a strong magnetic field. In addition, the charges are connected by a spring. In the limit of large magnetic field, the charges are frozen into the lowest Landau levels. Interactions of such particles include

Daniela Bigatti; Leonard Susskind

2000-01-01

177

Lattice Planar QED in external magnetic field  

E-print Network

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

Paolo Cea; Leonardo Cosmai; Pietro Giudice; Alessandro Papa

2011-09-29

178

Directional discontinuities in the interplanetary magnetic field  

Microsoft Academic Search

It is shown that the interplanetary magnetic field has different characteristics on different scales, and it is noted that a given physical theory may not be applicable or relevant on all scales. Four scales are defined in terms of time intervals on which the data may be viewed. Many discontinuities in the magnetic-field direction are seen on the mesoscale (

Leonard F. Burlaga

1969-01-01

179

Lattice Planar QED in external magnetic field  

NASA Astrophysics Data System (ADS)

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

Cea, P.; Cosmai, L.; Giudice, P.; Papa, A.

180

Ground Vehicle Navigation Using Magnetic Field Variation  

NASA Astrophysics Data System (ADS)

The Earth's magnetic field has been the bedrock of navigation for centuries. The latest research highlights the uniqueness of magnetic field measurements based on position due to large scale variations as well as localized perturbations. These observable changes in the Earth's magnetic field as a function of position provide distinct information which can be used for navigation. This dissertation describes ground vehicle navigation exploiting variation in Earth's magnetic field using a self-contained navigation system consisting of only a magnetometer and magnetic field maps. In order to achieve navigation, effective calibration enables repeatable magnetic field measurements from different vehicles and facilitates mapping of the observable magnetic field as a function of position. A new modified ellipsoid calibration technique for strapdown magnetometers in large vehicles is described, as well as analysis of position measurement generation comparing a multitude of measurement compositions using existing and newly developed likelihood techniques. Finally, navigation solutions are presented using both a position measurement and direct incorporation of the magnetometer measurements via a particle filter to demonstrate road navigation in three different environments. Emphatically, the results affirm that navigation using magnetic field variation in ground vehicles is viable and achieves adequate performance for road level navigation.

Shockley, Jeremiah A.

181

Astrophysical magnetic fields and nonlinear dynamo theory  

Microsoft Academic Search

The current understanding of astrophysical magnetic fields is reviewed, focusing on their generation and maintenance by turbulence. In the astrophysical context this generation is usually explained by a self-excited dynamo, which involves flows that can amplify a weak seed magnetic field exponentially fast. Particular emphasis is placed on the nonlinear saturation of the dynamo. Analytic and numerical results are discussed

Axel Brandenburg; Kandaswamy Subramanian

2005-01-01

182

Superconductor based sensor for monitoring magnetic field  

Microsoft Academic Search

The authors propose a method for measurement of magnetic fields with the help of a HTSC (high temperature superconductor) based sensor in conjunction with a microcomputer. The same sensor may be used for monitoring current in a circuit under the influence of a controlled magnetic field acting perpendicular to the direction of the current flow. The theoretical basis is discussed.

S. C. Kar; S. P. Basu

1992-01-01

183

Fall in Earth's magnetic field is erratic  

Microsoft Academic Search

Earth's magnetic field has decayed by about 5\\\\% per century since measurements began in 1840. Directional measurements predate those of intensity by more than 250 years, and we combined the global model of directions with paleomagnetic intensity measurements to estimate the fall in strength for this earlier period (1590 to 1840 A.D.). We found that magnetic field strength was nearly

David Gubbins; Adrian L. Jones; Christopher C. Finlay

2006-01-01

184

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

NASA Technical Reports Server (NTRS)

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

Burlaga, L. F.; Barouch, E.

1974-01-01

185

Permanent magnet edge-field quadrupole  

DOEpatents

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

Tatchyn, R.O.

1997-01-21

186

Permanent magnet edge-field quadrupole  

DOEpatents

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

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

187

Quenching of flames by magnetic fields  

Microsoft Academic Search

An experiment has been demonstrated to show a phenomenon involving quenching of candle flames using magnetic fields. An electromagnet with a pair of columnar magnetic poles in which inner sidepieces were hollowed out was used. Magnetic fields of 1.5 T at the brim gave a gradient of 50300 T\\/m in the direction perpendicular to the pole axis when the distance

S. Ueno

1989-01-01

188

Alignment of magnetic uniaxial particles in a magnetic field: Simulation  

NASA Astrophysics Data System (ADS)

The numerical investigations of the process of alignment of magnetically uniaxial Nd-Fe-B powders in an applied magnetic field were carried out using the discrete element method (DEM). It is shown that magnetic alignment of ensemble of spherical particles provides extremely high degree of alignment, which is achieved in low magnetic fields. A model of formation of anisotropic particles as a combination of spherical particles is suggested. The influence of the shape anisotropy and friction coefficient on the alignment degree was analyzed. The increase in the friction coefficient leads to a decrease in the alignment degree; the simulation results are in qualitative agreement with experimental dependences. It is shown that in magnetic fields higher than 5 T, the calculated field dependences of the alignment degree quantitatively render the experimental data. The increase of about 6% in the alignment degree in the experiments with addition of internal lubricant can be explained by the decrease of 14% in friction coefficient.

Golovnia, O. A.; Popov, A. G.; Sobolev, A. N.; Hadjipanayis, G. C.

2014-09-01

189

In vivo heating of magnetic nanoparticles in alternating magnetic field.  

PubMed

We have evaluated heating capabilities of new magnetic nanoparticles. In in vitro experiments they were exposed to an alternating magnetic field with frequency 3.5 MHz and induction 1.5 mT produced in three turn pancake coil. In in vivo experiments rats with injected magnetic nanoparticles were also exposed to an ac field. An optimal increase of temperature of the tumor to 44 degrees C was achieved after 10 minutes of exposure. Obtained results showed that magnetic nanoparticles may be easily heated in vitro as well as in vivo, and may be therefore useful for hyperthermic therapy of cancer. PMID:15377087

Babincov, M; Altanerov, V; Altaner, C; Cicmanec, P; Babinec, P

2004-08-01

190

Processing of polymers in high magnetic fields  

SciTech Connect

Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. This work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing. The liquid crystal thermoset chosen for this study is the diglycidyl ether of dihydroxy-{alpha}-methylstilbene cured with the diamine sulfamilamide. This thermoset has been cured at field strengths up to 18 Tesla.

Douglas, E.P.; Smith, M.E.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States); Earls, J.D.; Priester, R.D. Jr. [Dow Chemical Co., Freeport, TX (United States)

1996-05-01

191

Reionization constraints on primordial magnetic fields  

E-print Network

We study the impact of the extra density fluctuations induced by primordial magnetic fields on the reionization history in the redshift range: $6 magnetic fields (strength, $B_0$, and power-spectrum index $n_{\\scriptscriptstyle \\rm B}$), reionization, and $\\Lambda$CDM cosmological model. We find that magnetic field strengths in the range: $B_0 \\simeq 0.05{-}0.3$ nG (for nearly scale-free power spectra) can significantly alter the reionization history in the above redshift range and can relieve the tension between the WMAP and quasar absorption spectra data. Our analysis puts upper-limits on the magnetic field strength $B_0 magnetic field constraints among those available from other cosmological observables.

Pandey, Kanhaiya L; Sethi, Shiv K; Ferrara, Andrea

2014-01-01

192

Measurement of AC magnetic field distribution using magnetic resonance imaging.  

PubMed

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

Ider, Y Z; Muftuler, L T

1997-10-01

193

The Magnetic Field in the Solar Atmosphere  

E-print Network

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quie...

Wiegelmann, Thomas; Solanki, Sami K

2014-01-01

194

Magnetic Field Line Diffusion Footprints on Nonconformal NCSX First Wall  

NASA Astrophysics Data System (ADS)

The magnetic fields of the free boundary equilibria of the NCSX compact stellarator are calculated using VMEC and tabulated both inside and outside the LCMS by MFBE/2001 in a form suitable for field line tracing by both GOURDON and Kisslinger field line diffusion. Poincar'{e} plots of equilibrium configurations from 0 to 4/ beta both with and without island healing are made with emphasis placed on the mapping the edge between the LCMS and first wall. Footprints for each configuration on the actual non-conformal wall are found with field line diffusion calculations. Comparison is made with previous conformal wall calculations. It is found that more intersections occur at the close fitting wall at the 60r{ } cross-section than at the tips of the 0r{ } cross-section which has the largest flux expansion of the various cross-sections. Angles of incidence peak in the range 6-12r{ }. Footprints at low diffusion are similar to the high diffusion ones where step size of field line starting points are determined by anomalous thermal diffusivity. The starting surface is selected to be 1 to 2 cm inside the LCMS, and footprints are found to be independent of starting surface selection. An island structure possibly suitable for an island divertor concept is found in the absence of island healing. Other configurations lack islands in the SOL and may require an ergodic divertor concept. The variation of the footprint with beta and island healing is presented.

Grossman, Arthur

2005-10-01

195

Warm inflation in presence of magnetic fields  

E-print Network

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

Gabriella Piccinelli; Angel Sanchez; Alejandro Ayala; Ana Julia Mizher

2013-11-03

196

Bending of magnetic filaments under a magnetic field.  

PubMed

Magnetic beads and superparamagnetic (SP) colloid particles have successfully been employed for micromechanical manipulation of soft material, in situ probing of elastic properties, and design of smart materials (ferrogels). Here we derive analytical expressions for the equilibrium shape of magnetic fibers, considering two end-member cases, (a) SP or single-domain particles concentrated at the free end of cantilevered rods or tubes, and (b) filaments consisting of SP particles, with this case being mathematically equivalent to tubes containing SP particles. Our analysis yields also metastable equilibrium states (MES's), which only exist above a critical filament length, but become more stable with increasing magnetic field. The MES's for case (a) are, like the ground state, circular arcs, but more strongly bent. The multiform MES's in case (b), which comprise hairpin, sinuous, or even closed shapes, have recently been observed in experiments, too. We also study the effect of gravity on the balance between bending and magnetic energy, which leads to curves with inflection point if the influence of gravity is stronger than that of the magnetic field. Because of their simple experimental realization, case (a) magnetic filaments are deemed highly suitable for micromechanical experiments on long chains of polymer molecules. Another potential application of cantilevered magnetic filaments with magnetic material attached to the free end is in scanning probe microscopes. Because the magnetic field due to the magnetic tip is comparatively weak, the magnetization structure of the sample to be investigated would not be affected by the probe. Thus, for the examination of magnetically soft materials, probes in the form of magnetic filaments may hold advantages over tips usually employed in magnetic force microscopy. PMID:15697393

Shcherbakov, Valera P; Winklhofer, Michael

2004-12-01

197

Clean observations of magnetic field fluctuations on planetary surfaces  

Microsoft Academic Search

Magnetic field measurements on planetary surfaces are disturbed by various internal and external sources. We discuss methods to reduce their influence on the quality of magnetic field experiments aboard surface stations. Our major emphasis is on terrestrial seismo-magnetic measurements, but magnetic cleanliness procedures for the ROSETTA lander magnetic field experiment is discussed too. We consider not only disturbing magnetic field

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

2012-01-01

198

Casimir effect in external magnetic field  

E-print Network

In this paper we examine the Casimir effect for charged fields in presence of external magnetic field. We consider scalar field (connected with spinless particles) and the Dirac field (connected with 1/2-spin particles). In both cases we describe quantum field using the canonical formalism. We obtain vacuum energy by direct solving field equations and using the mode summation method. In order to compute the renormalized vacuum energy we use the Abel-Plana formula.

Marcin Ostrowski

2005-04-13

199

Magnetic fields in noninvasive brain stimulation.  

PubMed

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

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

2014-04-01

200

Magnetic monopole field exposed by electrons  

E-print Network

Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

Bch, A; Van Tendeloo, G; Verbeeck, J

2013-01-01

201

Origin of magnetic fields in galaxies  

SciTech Connect

Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial Universe (assumed to be random), predicted by the fluctuation -dissipation theorem, predicts {approx}0.034 {mu}G fields over {approx}0.3 kpc regions in galaxies. If the dipole magnetic fields predicted by the fluctuation-dissipation theorem are not completely random, microgauss fields over regions > or approx. 0.34 kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in < or approx. 10{sup 9} years in high redshift galaxies.

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

2010-03-15

202

Modeling solar force-free magnetic fields  

NASA Astrophysics Data System (ADS)

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy and the free energy associated with the electric current are finite and can be calculated directly from the magnetic field at the plane boundary using the virial theorem. In the study of solar magnetic fields with data from vector magnetographs, there is a long-standing interest in devising algorithms to extrapolate for the force-free magnetic field in a given domain from prescribed field values at the boundary. The closed-form magnetic fields of this paper open up an opportunity for testing the reliability and accuracy of algorithms that claim the capability of performing this extrapolation. The extrapolation procedure as an ill-posed mathematical problem is discussed.

Low, B. C.; Lou, Y. Q.

1990-03-01

203

Magnetic-field-controlled reconfigurable semiconductor logic.  

PubMed

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

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

2013-02-01

204

The Measurement of Magnetic Fields  

ERIC Educational Resources Information Center

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

Berridge, H. J. J.

1973-01-01

205

QCD vacuum structure in strong magnetic fields  

Microsoft Academic Search

We study the response of the QCD vacuum to strong magnetic fields, using a potential model for the quark-antiquark interaction. We find that production of spin-polarized u u pairs is energetically favorable for fields B > Bcrit ? 10 GeV2. We contrast the resulting uu condensate with the quark condensate which is present at zero magnetic field, and we estimate

Daniel Kabata; Kimyeong Leea; Erick Weinberg

206

Ohm's law for mean magnetic fields  

SciTech Connect

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

Boozer, A.H.

1986-05-01

207

An Extraordinary Magnetic Field Map of Mars  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

208

Ultrafast heating and magnetic switching with weak external magnetic field  

NASA Astrophysics Data System (ADS)

The TbFeCo magneto-optical media with the coercivity of bigger than 1.0 kOe are used for the investigation of ultrafast heating and magnetic switching with the weak external magnetic field. It has been found that the laser-induced active region becomes larger with an external magnetic field because the boundary of the active region is magnetized with the assistance of the external field during the ultrafast heating. According to this physical phenomenon, the so called "mark expansion method" has been proposed for visual observation of ultrafast switching marks. Using this method, the ultrafast magnetic switching in TbFeCo media has been studied using 40 fs laser pulse with linear polarization. The result shows that the ultrafast magnetic switching can be implemented by the laser pulse with assistance of the weak external field of about 0.7 kOe. Further studies show that the area percentage of the magnetic mark expansion relative to its thermal mark decreases with the increasing of the laser pulse energy. There exists the threshold pulse energy that the active region is fully magnetized. The theoretical analysis of electron, spin, and lattice temperatures has been conducted to the active region of the media where the maximum spin temperature is close to the Curie temperature of the media. The result indicates that the media become active at 4.137 ps and the ultrafast heating plays a key role for the ultrafast magnetic switching. The weak external magnetic field provides sufficient driving force to control the magnetization direction in the media.

Li, J. M.; Xu, B. X.; Zhang, J.; Ye, K. D.

2013-01-01

209

Tuning permanent magnets with adjustable field clamps  

SciTech Connect

The effective length of a permanent-magnet assembly can be varied by adjusting the geometrical parameters of a field clamp. This paper presents measurements on a representative dipole and quadrupole as the field clamp is withdrawn axially or radially. The detailed behavior depends upon the magnet multipolarity and geometry. As a rule-of-thumb, a 3-mm-thick iron plate placed at one end plane of the magnet will shorten the length by one-third of the magnet bore radius.

Schermer, R.I.

1987-01-01

210

Particle Transport in Therapeutic Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

Puri, Ishwar K.; Ganguly, Ranjan

2014-01-01

211

The CMS Magnetic Field Map Performance  

E-print Network

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field values. The value of the field at a given point of a volume is obtained by interpolation from a regular grid of values resulting from a TOSCA calculation or, when available, from a parameterization. The results of the measurements and calculations are presented, compared and discussed.

V. I. Klyukhin; N. Amapane; V. Andreev; A. Ball; B. Cur; A. Herv; A. Gaddi; H. Gerwig; V. Karimaki; R. Loveless; M. Mulders; S. Popescu; L. I. Sarycheva; T. Virdee

2011-10-04

212

Prediction of DC magnetic fields for magnetic cleanliness on spacecraft  

Microsoft Academic Search

Magnetometry is among the most used techniques in space exploration, e.g. to study complex plasma interactions between the solar wind and the Earth's magnetosphere, to map the planetary or interplanetary magnetic fields, or to retrieve information about the structural composition of planets. The success of each mission relies on the attainment of an adequate level of magnetic cleanliness at the

Axel Junge; Filippo Marliani

2011-01-01

213

Magnetic reconnection at the edge of Uranus's magnetic field  

NASA Astrophysics Data System (ADS)

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

Balcerak, Ernie

2014-09-01

214

Lunar surface remanent magnetic fields detected by the electron reflection method  

NASA Technical Reports Server (NTRS)

We present maps of the lunar surface remanent magnetic fields detected by the electron reflection method. These maps provide substantial coverage of the latitude band from 30 N southward to 30 S with a resolution of about 40 km and a sensitivity of about 0.2 gamma at the lunar surface. Regions of remanent magnetization are observed ranging in size from the resolution limit of 1.25 deg to above approximately 60 deg. The largest contiguous region fills the Big Backside Basin where it is intersected by the spacecraft orbital tracks. Preliminary analyses of the maps show that the source regions of lunar limb compressions correspond to regions of strong surface magnetism, and that there does not appear to be sharply discontinuous magnetization at the edges of maria. We also analyze the electron reflection observations to obtain information on the direction and distribution of magnetization in the Van de Graaff anomaly region.

Lin, R. P.; Anderson, K. A.; Bush, R.; Mcguire, R. E.; Mccoy, J. E.

1976-01-01

215

Magnetic field induced transition in vanadium spinels.  

PubMed

We study vanadium spinels AV2O4 (A = Cd,Mg) in pulsed magnetic fields up to 65 T. A jump in magnetization at ?0H?40??T is observed in the single-crystal MgV2O4, indicating a field induced quantum phase transition between two distinct magnetic orders. In the multiferroic CdV2O4, the field induced transition is accompanied by a suppression of the electric polarization. By modeling the magnetic properties in the presence of strong spin-orbit coupling characteristic of vanadium spinels, we show that both features of the field induced transition can be successfully explained by including the effects of the local trigonal crystal field. PMID:24483929

Mun, E D; Chern, Gia-Wei; Pardo, V; Rivadulla, F; Sinclair, R; Zhou, H D; Zapf, V S; Batista, C D

2014-01-10

216

Velocity-Magnetic Field Correlation of Pulsars  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar o rbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity, and the apparent correlat ion between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars, and consolidates the idea that the app arent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is cau sed by observational selection effects.

Itoh, N.; Kotouda, T.

217

ASYMMETRIC DIFFUSION OF MAGNETIC FIELD LINES  

SciTech Connect

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

Beresnyak, Andrey [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2013-04-20

218

Normal glow discharge in axial magnetic field  

NASA Astrophysics Data System (ADS)

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

Surzhikov, S.; Shang, J.

2014-10-01

219

Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields  

E-print Network

Tracing magnetic fields is crucial as magnetic fields play an important role in many astrophysical processes. Earlier studies have demonstrated that Ground State Alignment (GSA) is a unique way to detect weak magnetic fields (1G> B> 1exp(-15)G) in diffuse media, they consider the situation when the pumping source is a point source, which applies when the star is very far away from the diffuse media. In this paper, we explore the GSA in the presence of extended radiation fields. For the radiation fields with a clear geometric structure, we consider the alignment in circumstellar medium, binary systems, disc, and Local Interstellar Medium (LISM). For the radiation fields with unidentified pumping sources, we apply the method of multipole expansion and discuss the GSA induced by each component. We demonstrate that for general radiation fields, it is adequate to consider the contribution from dipole and quadrupole radiation components. We find that in general polarization of absorption arizing from GSA coincides ...

Zhang, Heshou; Dong, Le

2014-01-01

220

Quantum Electrodynamics in a Uniform Magnetic Field  

E-print Network

A systematic formalism for quantum electrodynamics in a classical uniform magnetic field is discussed. The first order radiative correction to the ground state energy of an electron is calculated. This then leads to the anomalous magnetic moment of an electron without divergent integrals. Thorough analyses of this problem are given for the weak magnetic field limit. A new expression for the radiative correction to the ground state energy is obtained. This contains only one integral with an additional summation with respect to each Landau level. The importance of this formalism is also addressed in order to deal with quantum electrodynamics in an intense external field.

Jun Suzuki

2005-12-28

221

Magnetic fields from second-order interactions  

E-print Network

It is well known that when two types of perturbations interact in cosmological perturbation theory, the interaction may lead to the generation of a third type. In this article we discuss the generation of magnetic fields from such interactions. We determine conditions under which the interaction of a first-order magnetic field with a first-order scalar-or vector-, or tensor-perturbations would lead to the generation of second order magnetic field. The analysis is done in a covariant-index-free approach, but could be done in the standard covariant indexed-approach.

Bob Osano

2014-03-21

222

Joule heating in high magnetic field pulsars  

E-print Network

We study the efficiency of Joule heating in the crustal layers of young neutron stars. It is shown that dissipation of the magnetic field is highly inhomogeneous in the crust with much faster dissipation in relatively low density layers. In young neutron stars, the rate of Joule heating in the crust can exceed the standard luminosity of non-magnetic star and can even be comparable to the luminosity of magnetars. The results of calculations are compared with the available observational data. We argue that the crustal field model can well account for the data on the surface temperature and magnetic field of young neutron stars.

Urpin, V

2008-01-01

223

Joule heating in high magnetic field pulsars  

E-print Network

We study the efficiency of Joule heating in the crustal layers of young neutron stars. It is shown that dissipation of the magnetic field is highly inhomogeneous in the crust with much faster dissipation in relatively low density layers. In young neutron stars, the rate of Joule heating in the crust can exceed the standard luminosity of non-magnetic star and can even be comparable to the luminosity of magnetars. The results of calculations are compared with the available observational data. We argue that the crustal field model can well account for the data on the surface temperature and magnetic field of young neutron stars.

V. Urpin; D. Konenkov

2008-04-01

224

Dynamo Models for Saturn's Axisymmetric Magnetic Field  

NASA Astrophysics Data System (ADS)

Magnetic field measurements by the Cassini mission have confirmed the earlier Pioneer 11 and Voyager missions' results that Saturn's observed magnetic field is extremely axisymmetric . For example, Saturn's dipole tilt is less than 0.06 degrees (Cao et al., 2011) . The nearly-perfect axisymmetry of Saturn's dipole is troubling because of Cowling's Theorem which states that an axisymmetric magnetic field cannot be maintained by a dynamo. However, Cowling's Theorem applies to the magnetic field generated inside the dynamo source region and we can avert any contradiction with Cowling's Theorem if we can find reason for a non-axisymmetric field generated inside the dynamo region to have an axisymmetrized potential field observed at satellite altitude. Stevenson (1980) proposed a mechanism for this axisymmetrization. He suggested that differential rotation in a stably-stratified electrically conducting layer (i.e. the helium rain-out layer) surrounding the dynamo could act to shear out the non-axisymmetry and hence produce an axisymmetric observed magnetic field. In previous work, we used three-dimensional self-consistent numerical dynamo models to demonstrate that a thin helium rain-out layer can produce a more axisymmetrized field (Stanley, 2010). We also found that the direction of the zonal flows in the layer is a crucial factor for magnetic field axisymmetry. Here we investigate the influence of the thickness of the helium rain-out layer and the intensity of the thermal winds on the axisymmetrization of the field. We search for optimal regions in parameter space for producing axisymmetric magnetic fields with similar spectral properties to the observed Saturnian field.

Stanley, S.; Tajdaran, K.

2012-12-01

225

On magnetic field generation in Kolmogorov turbulence  

E-print Network

We analyze the initial, kinematic stage of magnetic field evolution in an isotropic and homogeneous turbulent conducting fluid with a rough velocity field, v(l) ~ l^alpha, alphamagnetic Reynolds number that is needed to excite magnetic fluctuations. This implies that numerical or experimental investigations of the Kolmogorov turbulence with small Prandtl numbers need to achieve extremely high resolution in order to adequately describe magnetic phenomena; (ii) For small Prandtl numbers, magnetic energy penetrates below the resistive scale and has a power-law spectrum between the resistive and viscous scales. Magnetic energy is dissipated not at the resistive scale but at the much smaller viscous scale, which may be relevant for the problems of anomalous resistivity and fast magnetic reconnection. Our results also suggest that the l...

Boldyrev, S A; Boldyrev, Stanislav; Cattaneo, Fausto

2004-01-01

226

Recent biophysical studies in high magnetic fields  

NASA Astrophysics Data System (ADS)

A brief overview of biophysical effects of steady magnetic fields is given. The need of high field strength is illustrated by several recent diamagnetic orientation experiments. They include rod-like viruses, purple membranes and chromosomes. Results of various studies on bees, quails, rats and pigeons exposed to fields above 7 T are also resumed.

Maret, Georg

1990-06-01

227

Computer Program for Earths magnetic field  

Microsoft Academic Search

A FORTRAN IV computer program has been developed by the U.S. Coast and Geodetic Survey to compute the elements of the earths magnetic field for any geographic position.Part of the program is a mathematical model of the geomagnetic field consisting of two sets of spherical harmonic coefficients. The first set, representing the main geomagnetic field, consists of 168 coefficients (degree

Anonymous

1970-01-01

228

FEM Computation of Magnetic Fields in Anisotropic Magnetic Materials  

NASA Astrophysics Data System (ADS)

The magnetic fields in nonlinear anisotropic magnetic materials were analyzed by using the Finite Element Method (FEM). The measured data was directly used in the computation without a complicateded smoothing. The resultant asymmetric linear equations were solved by using the ILUBiCGStab method without symmetrization or the ICCG method with symmetrization. The magnetic flux distributions in a ring core model showed the characteristic patterns according to the non-oriented, grain-oriented and doubly-oriented magnetic properties. The good convergence of the Newton-Raphson nonlinear iteration was attained by the iterative solvers without special techniques for the smoothing.

Kameari, Akihisa; Fujiwara, Koji

229

TRANSITION REGION MAGNETIC FIELD AND POLAR MAGNETIC DISTURBANCES  

Microsoft Academic Search

The Explorer 12 measurements of the magnetic field outside the magnetosphere are compared with ground magnetograms from arctic observatories. Results indicate that an exterior field with a southerly component tends to be associated with ground disturbance, whereas a northward field is associated with quiet conditions. Examples are presented show- ing how a north-to-south field-direction change accompanies an increase in ground

D. H. Fairfield; L. J. Jr. Cahill

1966-01-01

230

Review: Magnetic fields of O stars  

E-print Network

Since 2002, strong, organized magnetic fields have been firmly detected at the surfaces of about 10 Galactic O-type stars. In this paper I will review the characteristics of the inferred fields of individual stars, as well as the overall population. I will discuss the extension of the 'magnetic desert', first inferred among the A-type stars, to O stars up to 60 solar masses. I will discuss the interaction of the winds of the magnetic stars with the fields above their surfaces, generating complex 'dynamical magnetosphere' structures detected in optical and UV lines, and in X-ray lines and continuum. Finally, I will discuss the detection of a small number of variable O stars in the LMC and SMC that exhibit spectral characteristics analogous to the known Galactic magnetic stars, and that almost certainly represent the first known examples of extra-Galactic magnetic stars.

Wade, G A

2014-01-01

231

Magnetic field effects on surgical ligation clips.  

PubMed

Magnetic forces exerted on surgical clips and the magnetic resonance imaging distortion they create in phantoms and rabbits at magnetic field strengths of 1.5 Tesla were investigated. Results are reported for both ligation and aneurysm clips manufactured from three types of stainless steel as well as titanium, tantalum and niobium metals. Paramagnetism and eddy currents were measured in a customized moving Gouy balance. Direct measurements of other magnetic forces were carried out in a 1.5T MRI system. The titanium and tantalum clips showed the least interaction with the magnetic field, both in terms of forces exerted and the observed image distortion with the larger clips generating the larger interactions. The strongest field distortions and attractive forces occurred with 17-7PH stainless steel clips. These interactions were ferromagnetic in origin and of sufficient strength to present significant risk to patients having this type of clip present during an MRI scan. PMID:3431354

Brown, M A; Carden, J A; Coleman, R E; McKinney, R; Spicer, L D

1987-01-01

232

The rotation-magnetic field relation  

NASA Astrophysics Data System (ADS)

Today, the generation of magnetic fields in solar-type stars and its relation to activity and rotation can coherently be explained, although it is certainly not understood in its entirety. Rotation facilitates the generation of magnetic flux that couples to the stellar wind, slowing down the star. There are still many open questions, particularly at early phases (young age), and at very low mass. It is vexing that rotational braking becomes inefficient at the threshold to fully convective interiors, although no threshold in magnetic activity is seen, and the generation of large scale magnetic fields is still possible for fully convective stars. This article briefly outlines our current understanding of the rotation-magnetic field relation.

Reiners, Ansgar; Scholz, Alexander; Eislffel, Jochen; Hallinan, Gregg; Berger, Edo; Browning, Matthew; Irwin, Jonathan; Kker, Manfred; Matt, Sean

2009-02-01

233

Electrical properties of chain microstructure magnetic emulsions in magnetic field  

E-print Network

The work deals with the experimental study of the emulsion whose dispersion medium is a magnetic fluid while the disperse phase is formed by a glycerin-water mixture. It is demonstrated that under effect of a magnetic field chain aggregates form from the disperse phase drops. Such emulsion microstructure change affects its macroscopic properties. The emulsion dielectric permeability and specific electrical conductivity have been measured. It is demonstrated that under the effect of relatively weak external magnetic fields (~ 1 kA/m) the emulsion electrical parameters may change several fold. The work theoretically analyzes the discovered regularities of the emulsion electrical properties.

Arthur Zakinyan; Yuri Dikansky; Marita Bedzhanyan

2014-02-05

234

Magnetic field generated by current filaments  

NASA Astrophysics Data System (ADS)

We investigate the magnetic field generated by two straight current filaments using the analogy between steady MHD and Euler flows. Using the Biot-Savart law, we present a dynamical system describing the extension of magnetic lines around the current filaments. It is demonstrated that, if two current filaments are non-parallel, a magnetic line starting near one current goes to infinity by the drifting effect of the other.

Kimura, Y.

2014-10-01

235

The earth's magnetic field: Its history, origin and planetary perspective  

Microsoft Academic Search

The history of geomagnetism and palaeomagnetism is examined, and an analysis and description of the present geomagnetic field is presented. The magnetic compass is discussed along with declination, inclination, secular variation, magnetic charts and the search for the poles, fossil magnetism and the magnetic field in the past, transient magnetic variations regarding the external magnetic field, the origin of the

R. T. Merrill; M. W. McElhinny

1983-01-01

236

Wire codes, magnetic fields, and childhood cancer  

SciTech Connect

Childhood cancer has been modestly associated with wire codes, an exposure surrogate for power frequency magnetic fields, but less consistently with measured fields. The authors analyzed data on the population distribution of wire codes and their relationship with several measured magnetic field metrics. In a given geographic area, there is a marked trend for decreased prevalence from low to high wire code categories, but there are differences between areas. For average measured fields, there is a positive relationship between the mean of the distributions and wire codes but a large overlap among the categories. Better discrimination is obtained for the extremes of the measurement values when comparing the highest and the lowest wire code categories. Instability of measurements, intermittent fields, or other exposure conditions do not appear to provide a viable explanation for the differences between wire codes and magnetic fields with respect to the strength and consistency of their respective association with childhood cancer.

Kheifets, L.I.; Kavet, R.; Sussman, S.S. [Electric Power Research Inst., Palo Alto, CA (United States)] [Electric Power Research Inst., Palo Alto, CA (United States)

1997-05-01

237

Magnetic space-based field measurements  

NASA Technical Reports Server (NTRS)

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

Langel, R. A.

1981-01-01

238

Cosmic Magnetic Fields and the CMB  

E-print Network

I describe the imprint of primordial magnetic fields on the CMB. I show that these are observable only if the field amplitude is of the order of $B\\gsim 10^{-9}G$ on Mpc scale. I further argue that such fields are strongly constrained by the stochastic background of gravity waves which they produce. Primordial magnetic fields, which are strong enough to be seen in the CMB, are compatible with the nucleosynthesis bound, only if their spectrum is close to scale invariant, or maybe if helical magnetic fields provoke an inverse cascade. For helical fields, the CMB signature is especially interesting. It contains parity violating T-B and E--B correlations.

Ruth Durrer

2006-09-08

239

Magnetic Dipole Field 3D Model  

NSDL National Science Digital Library

The Magnetic Dipole Field 3D Model displays the field lines and field vectors of a dipole located at the origin and oriented along the z-axis. Users can compute the field line passing through a point by dragging the a marker within the 3D view. Users can also visualize the field vectors in a plane passing though the center of the dipole. The Magnetic Dipole Field 3D Model was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_MagneticDipole3D.jar file will run the program if Java is installed. EJS is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models.

Christian, Wolfgang

2012-08-11

240

Rotation of the Earth's Magnetic Field  

Microsoft Academic Search

HALLEY1 first noticed that the magnetic declination at a number of sites changed with time in a manner that was consistent with a steady westward drift of the magnetic field relative to the surface of the Earth. After long neglect, interest in westward drift was revived by the work of Bullard et al.2, who examined the westward drift of the

S. R. C. Malin; I. Saunders

1973-01-01

241

End fields of CBA superconducting magnets  

SciTech Connect

Measurements of the two dimensional harmonic content of the end fields generated by the Brookhaven CBA dipole and quadrupole superconducting magnets are presented. Both the local longitudinal structure and the integrated end effects are examined.

Kirk, H.G.; Herrera, J.; Willen, E.

1983-01-01

242

Magnetic Field Response Measurement Acquisition System  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

243

Magnetic Field Response Measurement Acquisition System  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

244

Vacuum Birefringence in Strong Magnetic Fields  

Microsoft Academic Search

Table of Contents 1. One-loop effective Lagrangian in spinor QED. 2. Dispersion effects for low-frequency photons. 3. Vacuum birefringence in magnetic fields. 4. Light cone condition, effective Lagrangian approach.

Walter Dittrich; Holger Gies

1998-01-01

245

Fractal structure of the interplanetary magnetic field  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

246

Lunar magnetic field measurements with a cubesat  

E-print Network

We have developed a mission concept that uses 3-unit cubesats to perform new measurements of lunar magnetic fields, less than 100 meters above the Moons surface. The mission calls for sending the cubesats on impact ...

Garrick-Bethell, Ian

247

Laminated magnet field coil sheath  

DOEpatents

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

Skaritka, John R. (Coram, NY)

1987-12-01

248

Laminated magnet field coil sheath  

DOEpatents

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

Skaritka, J.R.

1987-05-15

249

Bi2212\\/Ag high-field magnets  

Microsoft Academic Search

Bi-2212\\/Ag conductors show practical transport properties in high magnetic field regions above 20 T and 4.2 K, where it is considered difficult to use metallic superconductors. In this paper, the recent progress of our development of Bi-2212\\/Ag high field insert magnets is presented. Bi-2212\\/Ag stacked double pancake coils with a 49150 mm outer diameter, 1565 mm inner diameter and 50220

M. Okada; K. Tanaka; T. Wakuda; K. Ohata; J. Sato; T. Kiyoshi; H. Kitaguchi; H. Wada

2000-01-01

250

The magnetic field investigation on Cluster  

NASA Technical Reports Server (NTRS)

The magnetic field investigation of the Cluster four-spacecraft mission is designed to provide intercalibrated measurements of the B magnetic field vector. The instrumentation and data processing of the mission are discussed. The instrumentation is identical on the four spacecraft. It consists of two triaxial fluxgate sensors and of a failure tolerant data processing unit. The combined analysis of the four spacecraft data will yield such parameters as the current density vector, wave vectors, and the geometry and structure of discontinuities.

Balogh, A.; Cowley, S. W. H.; Southwood, D. J.; Musmann, G.; Luhr, H.; Neubauer, F. M.; Glassmeier, K.-H.; Riedler, W.; Heyn, M. F.; Acuna, M. H.

1988-01-01

251

Mean-field quantum dynamics with magnetic fields  

E-print Network

We consider a system of $N$ bosons in three dimensions interacting through a mean-field Coulomb potential in an external magnetic field. For initially factorized states we show that the one-particle density matrix associated with the solution of the $N$-body Schr\\"odinger equation converges to the projection onto the solution of the magnetic Hartree equation in trace norm and in energy as $N \\rightarrow \\infty$. Estimates on the rate of convergence are provided.

Jonas Luhrmann

2012-02-06

252

Magnetic field transfer device and method  

DOEpatents

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

Wipf, S.L.

1990-02-13

253

Dynamic signatures of quiet sun magnetic fields  

NASA Technical Reports Server (NTRS)

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

Martin, S. F.

1983-01-01

254

Particle decay in Ising field theory with magnetic field  

E-print Network

The scaling limit of the two-dimensional Ising model in the plane of temperature and magnetic field defines a field theory which provides the simplest illustration of non-trivial phenomena such as spontaneous symmetry breaking and confinement. Here we discuss how Ising field theory also gives the simplest model for particle decay. The decay widths computed in this theory provide the obvious test ground for the numerical methods designed to study unstable particles in quantum field theories discretized on a lattice.

Gesualdo Delfino

2007-03-30

255

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

E-print Network

Levin and Ernst, DC Magnetic Field Effects on Development Applied DC Magnetic Fields Cause relative to fertilization. The exposure time which caused the maximum effect differed between the two urchin, static magnetic field, gastrulation, development, mitotic cycle, teratogenic effects running

Levin, Michael

256

Effects of static magnetic fields on plants.  

NASA Astrophysics Data System (ADS)

In our recent experiment on STS-107 (MFA-Biotube) we took advantage of the magnetic heterogeneity of the gravity receptor cells of flax roots, namely stronger diamagnetism of starch-filled amyloplasts compared to cytoplasm (? ? < 0). High gradient magnetic fields (HGMF, grad(H2/2) up to 109-1010 Oe2/cm) of the experimental chambers (MFCs) repelled amyloplasts from the zones of stronger field thus providing a directional stimulus for plant gravisensing system in microgravity, and causing the roots to react. Such reaction was observed in the video downlink pictures. Unfortunately, the ``Columbia'' tragedy caused loss of the plant material and most of the images, thus preventing us from detailed studies of the results. Currently we are looking for a possibility to repeat this experiment. Therefore, it is very important to understand, what other effects (besides displacing amyloplasts) static magnetic fields with intensities 0 to 2.5104 Oe, and with the size of the area of non-uniformity 10-3 to 1 cm. These effects were estimated theoretically and tested experimentally. No statistically significant differences in growth rates or rates of gravicurvature were observed in experiments with Linum, Arabidopsis, Hordeum, Avena, Ceratodon and Chara between the plants grown in uniform magnetic fields of various intensities (102 to 2.5104 Oe) and those grown in the Earth's magnetic field. Microscopic studies also did not detect any structural differences between test and control plants. The magnitudes of possible effects of static magnetic fields on plant cells and organs (including effects on ion currents, magneto-hydrodynamic effects in moving cytoplasm, ponderomotive forces on other cellular structures, effects on some biochemical reactions and biomolecules) were estimated theoretically. The estimations have shown, that these effects are small compared to the thermodynamic noise and thus are insignificant. Both theoretical estimations and control experiments confirm, that intracellular magnetophoresis of statoliths is the only significant effect of the magnetic field on plant cells and organs in the tested magnetic systems.

Kuznetsov, O.

257

Magnetic field structure evolution in RMF plasmas  

NASA Astrophysics Data System (ADS)

A study of magnetic field structure evolution during 40-ms plasma discharge had been performed in 80 cm long / 40 cm OD cylindrical chamber. Plasma current Ip2--3 kA is produced by applied 500 kHz rotating magnetic field. In experiments, the 2D profile of plasma current is changed by feeding a 10-ms pulse current to additional magnetic coil located at the midplane. Using newly developed magnetic field pick-up coils system, we scanned the magnetic field in cross-section of plasma. Two experimental regimes were studied: without external toroidal field (TF), and with TF produced by applied axial current. When a relatively small current (<0.5 kA) is applied to the midplane coil, in both cases the total plasma current measured with Rogowski coil experiences a jump (up to 100%), but the profile of current remains almost unchanged. When a larger current (1--2 kA) is applied to the midplane coil, the total plasma current drops; the magnetic structure changes differently in two regimes. In regime without TF, the magnetic field of plasma current is reversed at Rmagnetic field evolves during initial 1--3 ms transitional period of plasma formation.

Petrov, Yuri; Yang, Xiaokang; Huang, Tian-Sen

2007-11-01

258

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

SciTech Connect

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

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

1998-08-22

259

Magnetic marker based homogeneous bioassays utilizing rotating magnetic fields  

NASA Astrophysics Data System (ADS)

Magnetic nanoparticles (MNPs) as markers in bioassays utilizing rotating instead of alternating magnetic fields predict an improved sensitivity regarding quantitative protein detection. This finding is based on numerical solutions of the Fokker-Planck equation and pronounced for increasing field amplitudes. In order to verify this prediction, the phase lag change of MNPs in rotating magnetic fields up to 5 mT is measured. The magnetic markers are functionalized single core iron oxide nanoparticles with different sizes. Antibodies which specifically bind to the MNPs cause the phase lag change. The increase of the phase lag change strongly depends on the particle parameters. MNPs with a core diameter of 30 nm show for 5 mT, a significant difference between the two field types. This difference is less pronounced for the 25 nm MNPs due to the increasing influence of Nel relaxation processes and for the 40 nm particles, due to the reduced saturation magnetization. A further improvement for the 30 nm MNPs with field amplitudes over 5 mT is simulated based on the determined particle parameters.

Dieckhoff, Jan; Schilling, Meinhard; Ludwig, Frank

2014-05-01

260

Magnetic fields of Jupiter and Saturn  

SciTech Connect

The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

Ness, N.F.

1981-01-01

261

Slowly rotating pulsars and magnetic field decay  

NASA Astrophysics Data System (ADS)

Two dozen long period pulsars are separated from the swarm of ordinary pulsars by an obvious gap in the P versus Sd diagram (where Sd=log?(P)+21.0), with a plausible upper boundary for ordinary pulsars. Possible pulsar evolutionary tracks are discussed to explain the diagram in terms of previously suggested scenarios of magnetic field decay. The (P-Sd) diagram is difficult to understand if there is no magnetic field decay during the active life of pulsars. However, if the magnetic fields of neutron stars decay exponentially, almost all slowly rotating pulsars must have been injected with a very long initial spin period of about 2 seconds, which seems impossible. Based on qualitative analyses, it is concluded that magnetic fields of neutron stars decay as a power-law, with a time scale related to the initial field strengths. The plausible boundary and the gap are suggested to naturally divide pulsars with distinct magnetic "genes", ie. pulsars which were born from strongly magnetized progenitors -- such as Bp stars, and pulsars born from normal massive stars. The possibility remains open that a fraction of slowly rotating pulsars were injected with long initial spin periods, while others would have a classical pulsar evolution history. It is suggested that PSR B1849+00 was born in the supernova remnant Kes-79 with an initial period of about 2 seconds.

Han, J. L.

1997-02-01

262

Stabilizing textures with magnetic fields  

E-print Network

The best-known way of stabilizing textures is by Skyrme-like terms, but another possibility is to use gauge fields. The semilocal vortex may be viewed as an example of this, in two spatial dimensions. In three dimensions, however, the idea (in its simplest form) does not work -- the link between the gauge field and the scalar field is not strong enough to prevent the texture from collapsing. Modifying the |D Phi|^2 term in the Lagrangian (essentially by changing the metric on the Phi-space) can strengthen this link, and lead to stability. Furthermore, there is a limit in which the gauge field is entirely determined in terms of the scalar field, and the system reduces to a pure Skyrme-like one. This is described for gauge group U(1), in dimensions two and three. The non-abelian version is discussed briefly, but as yet no examples of texture stabilization are known in this case.

R S Ward

2002-07-11

263

Plasma separation from magnetic field lines in a magnetic nozzle  

NASA Technical Reports Server (NTRS)

This paper discusses conditions for separation of a plasma from the magnetic field of a magnetic nozzle. The analysis assumes a collisionless, quasineutral plasma, and therefore the results represent a lower bound on the amount of detachment possible for a given set of plasma conditions. We show that collisionless separation can occur because finite electron mass inhibits the flow of azimuthal currents in the nozzle. Separation conditions are governed by a parameter G which depends on plasma and nozzle conditions. Several methods of improving plasma detachment are presented, including moving the plasma generation zone downstream from the region of strongest magnetic field and using dual magnets to focus the plasma beam. Plasma detachment can be enhanced by manipulation of the nozzle configuration.

Kaufman, D. A.; Goodwin, D. G.; Sercel, J. C.

1993-01-01

264

Lightning Magnetic Field Measurements around Langmuir Laboratory  

NASA Astrophysics Data System (ADS)

In the absence of artificial conductors, underground lightning transients are produced by diffusion of the horizontal surface magnetic field of a return stroke vertically downward into the conducting earth. The changing magnetic flux produces an orthogonal horizontal electric field, generating a dispersive, lossy transverse electromagnetic wave that penetrates a hundred meters or more into the ground according to the skin depth of the medium. In turn, the electric field produces currents that flow toward or away from the channel to ground depending on the stroke polarity. The underground transients can produce large radial horizontal potential gradients depending on the distance from the discharge and depth below the surface. In this study we focus on the surface excitation field. The goal of the work is to compare measurements of surface magnetic field waveforms B(t) at different distances from natural lightning discharges with simple and detailed models of the return stroke fields. In addition to providing input to the diffusion mechanism, the results should aid in further understanding return stroke field generation processes. The observational data are to be obtained using orthogonal sets of straightened Rogowski coils to measure magnetic field waveforms in N-S and E-W directions. The waveforms are sampled at 500 kS/s over 1.024 second time intervals and recorded directly onto secure digital cards. The instrument operates off of battery power for several days or weeks at a time in remote, unattended locations and measures magnetic field strengths of up to several tens of amperes/meter. The observations are being made in conjunction with collocated slow electric field change measurements and under good 3-D lightning mapping array (LMA) and fast electric field change coverage.

Stock, M.; Krehbiel, P. R.; Rison, W.; Aulich, G. D.; Edens, H. E.; Sonnenfeld, R. G.

2010-12-01

265

The magnetic field of the Milky Way  

Microsoft Academic Search

Since its discovery 40 years ago as a confiner of cosmic rays and an aligner of interstellar dust grains, the Galactic magnetic field has been studied through emission and polarization of synchrotron radiation, Faraday rotation, Zeeman splitting, and effects on gas flows and morphology. The local field has a coherent, few microgauss, component roughly along the local spiral arm and

Virginia Trimble

1990-01-01

266

Vacuum polarization tensor in inhomogeneous magnetic fields  

Microsoft Academic Search

We develop worldline numerical methods, which combine string-inspired with Monte Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field.

Holger Gies; Lars Roessler

2011-01-01

267

Magnetic field generation from nonequilibrium phase transitions  

Microsoft Academic Search

We study the generation of magnetic fields during the stage of particle production resulting from spinodal instabilities during phase transitions out of equilibrium. The main premise is that long-wavelength instabilities that drive the phase transition lead to strong nonequilibrium charge and current fluctuations which generate electromagnetic fields. We present a formulation based on the nonequilibrium Schwinger-Dyson equations that leads to

D. Boyanovsky; H. J. de Vega; M. Simionato

2003-01-01

268

Magnetic field effects on CRT computer monitors  

Microsoft Academic Search

This paper discusses the effect of external low frequency magnetic field interference on cathode ray tube (CRT) computer monitors. The paper describes a new test facility and presents a quantitative measuring method which has been developed to characterize the field effects. A total of 21 monitors from major manufacturers were tested. It was found that larger monitors are more sensitive

Balazs Banfai; George G. Karady; Charles J. Kim; Kate Brown Maracas

2000-01-01

269

Cosmic rays in the earth's magnetic field  

Microsoft Academic Search

It is shown that the values of cosmic ray cut-off moments in the earth's magnetic field, observed at many different places, are generally close to the values calculated from Strmer's theory for the motion of charged particles in a dipole field, if the usual centre dipole of the earth is replaced in the Strmer equation by a dipole whose magnitude

P. Rothwell

1958-01-01

270

Hydrogen atom in a strong magnetic field  

NASA Astrophysics Data System (ADS)

We study the energy spectrum of atomic hydrogen in strong ( B \\gt B_a\\sim 10^9 G) and ultra-strong ( B \\gtrsim B_cr \\sim 10^{14} G) magnetic fields, in which the hydrogen electron starts to move relativistically and quantum electrodynamics effects become important. Within the adiabatic approximation, highly accurate energy level values are obtained analytically for B \\gt 10^{11} G, which are then compared with asymptotic and numerical results available in the literature. A characteristic feature noted in electron motion in a strong magnetic field is that for B \\gtrsim B_cr, the transverse motion becomes relativistic, while the longitudinal motion (along B) can be described by nonrelativistic theory and is amenable to the adiabatic approximation. Topics discussed include: the qualitative difference in the way odd and even levels change with the magnetic field (for B \\gg B_a); the removal of degeneracy between odd and even atomic states; spectral scaling relations for different quantum numbers (n, n_\\rho, m) and different field strengths; the shape, size, and quadrupole moment of the atom for B \\gg B_a; radiative transitions np\\to 1s in a strong magnetic field; relativistic QED effects, including the effects of vacuum polarization and of the electron anomalous magnetic moment on the energy level positions; Coulomb potential screening and energy level freezing at B\\to \\infty ; and the possibility of the Zeldovich effect in the hydrogen spectrum in a strong magnetic field. The critical nuclear charge problem is briefly discussed. Simple asymptotic formulas for Z_cr, valid for low-lying levels, are proposed. Some of the available information on extreme magnetic fields produced in the laboratory and occurring in space is given. The Coulomb renormalization of the scattering length is considered in the resonance situation with a shallow level in the spectrum.

Popov, V. S.; Karnakov, B. M.

2014-03-01

271

Magnetic nanoparticles for applications in oscillating magnetic field  

SciTech Connect

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

Peeraphatdit, Chorthip

2010-12-15

272

Circumstellar Magnetic Field Diagnostics from Line Polarization  

E-print Network

Given that dynamically significant magnetic fields in at least some massive stars have now been measured, our contribution addresses the question, to what extent can fields be directly detected in circumstellar gas? The question speaks directly to the very interesting topic of line-driving physics coupled with magnetized plasmas, and how this coupling produces structure in the wind flow. We focus our attention on weak-field diagnostics. These come in two main types: the Hanle effect, which pertains to coherence effects for linear polarization from line scattering, and the weak longitudinal Zeeman effect, which pertains to circular polarization in lines.

Richard Ignace; Kenneth G. Gayley

2007-08-14

273

Nonperturbative Physics in a Magnetic Field  

E-print Network

Non-Perturbative Quantum Field Theory has played an important role in the study of phenomena where a fermion condensate can appear under certain physical conditions. The familiar phenomenon of electric superconductivity, the color superconductivity of very dense quark matter, and the chiral symmetry breaking of low energy effective chiral theories are all examples of that sort. Often one is interested in the behavior of these systems in the presence of an external magnetic field. In this talk I will outline the effects of an external magnetic field on theories with either fermion-fermion or fermion-antifermion condensates.

Vivian de la Incera

2010-04-28

274

Opening the cusp. [using magnetic field topology  

NASA Technical Reports Server (NTRS)

This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

1991-01-01

275

Self-induced quasistationary magnetic fields  

SciTech Connect

The interaction of electromagnetic radiation with temporally dispersive magnetic solids of small dimensions may show very special resonant behaviors. The internal fields of such samples are characterized by magnetostatic-potential scalar wave functions. The oscillating modes have the energy orthogonality properties and unusual pseudoelectric (gauge) fields. Because of a phase factor, that makes the states single valued, a persistent magnetic current exists. This leads to appearance of an eigenelectric moment of a small disk sample. One of the intriguing features of the mode fields is dynamical symmetry breaking.

Kamenetskii, E. O. [Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer Sheva 84105 (Israel)

2006-01-15

276

Varying Electromagnetic Coupling and Primordial Magnetic Fields  

E-print Network

We study the effect of variations of the electromagnetic coupling on the process of generation of primordial magnetic fields. We find that only through a significant growth of the electromagnetic coupling minimum seed fields can be produced. We also show that, if through some process in the early Universe the photon acquires a mass that leads, thanks to inflation, to the generation of primordial magnetic fields, then the influence of variations of the electromagnetic coupling amounts essentially to the results due to the photon effective mass alone.

O. Bertolami; R. Monteiro

2005-04-08

277

Plasma heating in a variable magnetic field  

SciTech Connect

The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfven.

Kichigin, G. N., E-mail: king@iszf.irk.ru [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics (Russian Federation)

2013-05-15

278

Assessment of inhomogeneous ELF magnetic field exposures.  

PubMed

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts. PMID:18407972

Leitgeb, N; Cech, R; Schrttner, J

2008-01-01

279

Neutrino Processes in Strong Magnetic Fields  

E-print Network

The processes of electron neutrino capture on neutron and electron anti-neutrino capture on proton, and their reverse processes provide the dominant mechanisms for heating and cooling the material below the stalled shock in a core-collapse supernova. We summarize the major effects of strong magnetic fields on the rates of the above reactions and illustrate these effects with a simple supernova model. Due to parity violation of weak interaction the heating rates are asymmetric even for a uniform magnetic field. The cooling rates are also asymmetric for nonuniform fields. The most dramatic effect of strong magnetic fields of 10^16 G is suppression of the cooling rates by changing the equations of state through the phase space of electrons and positrons.

Huaiyu Duan; Yong-Zhong Qian

2005-06-07

280

Magnetic Fields on the Surface of the Sun  

NSDL National Science Digital Library

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

281

Magnetic field structure in Monoceros R2  

NASA Technical Reports Server (NTRS)

We have carried out polarimetric observations to investigate the geometry of the magnetic field in the giant molecular cloud Monoceros R2. This study is based upon deep R-band charge coupled device (CCD) polarimetry, covering a total area of 0.5 deg(exp 2) of the giant molecular cloud. The data were calibrated using a new technique that relies on obtaining broad-band photometry of stars simultaneously with polarimetric photometry of the Mon R2 fields, thus providing an accurate means of measuring the electric vectors of starlight which is polarized by the fore-ground dust grains aligned by the magnetic field in the Mon R2 GMC. In this work, (1) we were able to continuously trace magnetic field lines from the largest scales in Mon R2 to the detailed structure of the field in the dense core, as determined from infrared polarimetry; and (2) we have found that the ambient field is apparently modified by a large-scale structure in the Mon R2 cloud. The mean angle of polarization for the complete sample we measured is 158 deg, which is roughly coincident with the local Galactic magnetic field (155 deg). The dispersion in the angle of polarization is 33 deg, similar to that found in the Orion GMC. The dispersion in angle of polarization for stars located along the western side of the three CCD fields is 22 deg. The CCD fields are bisected by a dense ridge of gas defining the boundary of an expanding gas shell that recent observational results at millimeter wavelengths now reveal dominates the Mon R2 GMC. Our results suggest th at the expanding shell has distorted the magnetic field lines extending from the core to the northern gas structure comprising Mon R2.

Jarrett, T. H.; Novak, G.; Xie, T.; Goldsmith, P. F.

1994-01-01

282

Vacuum polarization tensor in inhomogeneous magnetic fields  

E-print Network

We develop worldline numerical methods, which combine string-inspired with Monte-Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field. Whereas a local derivative expansion applies to the limit of small variations compared to the Compton wavelength, the case of a strongly varying field can be approximated by a derivative expansion for the averaged field. For rapidly varying fields, the vacuum-magnetic refractive indices can exhibit a non-monotonic dependence on the local field strength. This behavior can provide a natural limit on the self-focussing property of the quantum vacuum.

Gies, Holger

2011-01-01

283

Vacuum polarization tensor in inhomogeneous magnetic fields  

E-print Network

We develop worldline numerical methods, which combine string-inspired with Monte-Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field. Whereas a local derivative expansion applies to the limit of small variations compared to the Compton wavelength, the case of a strongly varying field can be approximated by a derivative expansion for the averaged field. For rapidly varying fields, the vacuum-magnetic refractive indices can exhibit a non-monotonic dependence on the local field strength. This behavior can provide a natural limit on the self-focussing property of the quantum vacuum.

Holger Gies; Lars Roessler

2011-07-01

284

Vacuum polarization tensor in inhomogeneous magnetic fields  

NASA Astrophysics Data System (ADS)

We develop worldline numerical methods, which combine string-inspired with Monte Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field. Whereas a local derivative expansion applies to the limit of small variations compared to the Compton wavelength, the case of a strongly varying field can be approximated by a derivative expansion for the averaged field. For rapidly varying fields, the vacuum-magnetic refractive indices can exhibit a nonmonotonic dependence on the local field strength. This behavior can provide a natural limit on the self-focussing property of the quantum vacuum.

Gies, Holger; Roessler, Lars

2011-09-01

285

Stable magnetic fields in stellar interiors  

NASA Astrophysics Data System (ADS)

We investigate the 50-year old hypothesis that the magnetic fields of the Ap stars are stable equilibria that have survived in these stars since their formation. With numerical simulations we find that stable magnetic field configurations indeed appear to exist under the conditions in the radiative interior of a star. Confirming a hypothesis by Prendergast (1956, ApJ, 123, 498), the configurations have roughly equal poloidal and toroidal field strengths. We find that tori of such twisted fields can form as remnants of the decay of an unstable random initial field. In agreement with observations, the appearance at the surface is an approximate dipole with smaller contributions from higher multipoles, and the surface field strength can increase with the age of the star. The results of this paper were summarised by Braithwaite & Spruit (2004, Nature, 431, 891).

Braithwaite, J.; Nordlund, .

2006-05-01

286

The stability of toroidal magnetic fields with equatorial symmetry: implications for the Earth's magnetic field  

Microsoft Academic Search

Geophysical observation suggests that the symmetry of the Earth's magnetic field has been predominantly dipolar over the last 2.5 m.y. Given that such an antisymmetric field will vanish at the equatorial plane, we might expect antisymmetry to be a source of magnetic field instability, as the presence of so-called critical surfaces are robust destabilising features, independent of field morphology. To

Kenneth A. Hutcheson; David R. Fearn

1996-01-01

287

Hall Magnetic Reconnection: Guide Field Dependence  

Microsoft Academic Search

Two (2D) and three (3D) dimensional Hall magnetohydrodynamic (MHD) simulations are used to study the dependence of a guide field on magnetic reconnection. The 2D simulations are run until a steady state is achieved for B gf\\/B0 = 0, 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 where B gf is the guide field and B0 is the reversed field. It

L. Rudakov; J. Huba

2004-01-01

288

Magnetic Field Response Measurement Acquisition System  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

289

Holographic Gauge Theory with Maxwell Magnetic Field  

E-print Network

We first apply the transformation of mixing azimuthal with wrapped coordinate to the 11D M-theory with a stack N M5-branes to find the spacetime of a stack of N D4-branes with magnetic field in 10D IIA string theory, after the Kaluza-Klein reduction. In the near-horizon limit the background becomes the Melvin magnetic field deformed $AdS_6 \\times S^4$. Although the solution represents the D-branes under the Melvin RR one-form we use a simple observation to see that it also describes the solution of D-branes under the Maxwell magnetic field. As the magnetic field we consider is the part of the background itself we have presented an alternative to previous literature, because our method does not require the assumption of negligible back reaction. Next, we use the found solution to investigate the meson property through D4/D8 system (Sakai-Sugimoto model) and compare it with those studied by other authors. Finally, we present a detailed analysis about the Wilson loop therein and results show that the external Maxwell magnetic field will enhance the quark-antiquark potential.

Wung-Hong Huang

2009-04-15

290

Measurement of the CMS Magnetic Field  

E-print Network

The measurement of the magnetic field in the tracking volume inside the superconducting coil of the Compact Muon Solenoid (CMS) detector under construction at CERN is done with a fieldmapper designed and produced at Fermilab. The fieldmapper uses 10 3-D B-sensors (Hall probes) developed at NIKHEF and calibrated at CERN to precision 0.05% for a nominal 4 T field. The precise fieldmapper measurements are done in 33840 points inside a cylinder of 1.724 m radius and 7 m long at central fields of 2, 3, 3.5, 3.8, and 4 T. Three components of the magnetic flux density at the CMS coil maximum excitation and the remanent fields on the steel-air interface after discharge of the coil are measured in check-points with 95 3-D B-sensors located near the magnetic flux return yoke elements. Voltages induced in 22 flux-loops made of 405-turn installed on selected segments of the yoke are sampled online during the entire fast discharge (190 s time-constant) of the CMS coil and integrated offline to provide a measurement of the initial magnetic flux density in steel at the maximum field to an accuracy of a few percent. The results of the measurements made at 4 T are reported and compared with a three-dimensional model of the CMS magnet system calculated with TOSCA.

V. I. Klyukhin; A. Ball; F. Bergsma; D. Campi; B. Cur; A. Gaddi; H. Gerwig; A. Herv; J. Korienek; F. Linde; C. Lindenmeyer; R. Loveless; M. Mulders; T. Nebel; R. P. Smith; D. Stickland; G. Teafoe; L. Veillet; J. K. Zimmerman

2011-10-03

291

Reducing blood viscosity with magnetic fields  

NASA Astrophysics Data System (ADS)

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

Tao, R.; Huang, K.

2011-07-01

292

Magnetic Fields and Massive Star Formation  

E-print Network

Massive stars ($M > 8$ \\msun) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 $\\mu$m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of $\\lsim$ 0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within $40^\\circ$ of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the ...

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

2014-01-01

293

Magnetic Field Noise Changes Effect of Combined Magnetic Field on Gravitropic Reaction of Cress Roots.  

NASA Astrophysics Data System (ADS)

The gravitropic reaction of cress roots in combined magnetic field was studied in details. It was shown that the negative roots gravitropism observed at the frequency of alternating component of combined magnetic field adjusted to the Ca ion cyclotron frequency could be observed only at Nayquist magnetic field noise level under 5 nT/Hz. While the magnetic noise level was increasing the negative gravitropism was disappearing. The inhibition of gravitropic reaction was observed in all cases. The effect was accompanied by the changes in the noise spectrum generated by cress roots.

Bogatina, Nina; Kordyum, Elizabeth; Sheykina, Nadezhda

294

Computing nonlinear force free coronal magnetic fields  

E-print Network

Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

T. Wiegelmann; T. Neukirch

2008-01-21

295

Topology of induced lunar magnetic fields  

NASA Technical Reports Server (NTRS)

Using the asymmetric theory of lunar induction the total and induced magnetic field line structure within the Moon and the diamagnetic cavity were obtained. Total field distributions are shown for orientations of the oscillating interplanetary field parallel, perpendicular and at 45 deg to the cavity axis. Induced field lines are shown only for the orientations of the interplanetary field parallel and orthogonal to the cavity axis. When compared with the field lines derived using the long wavelength limit of spherically symmetric vacuum induction theory, the configurations obtained using the asymmetric theory exhibit significant distortion. For all orientations of the interplanetary field, the field lines are strongly compressed on the sunlit hemisphere because of the confining solar wind pressure at the lunar surface and the exclusion of the field by the lunar core.

Schwartz, K.; Schubert, G.

1973-01-01

296

The Cassini Magnetic Field Investigation  

Microsoft Academic Search

The dual technique magnetometer system onboard the Cassini orbiter is described. This instrument consists of vector helium and fluxgate magnetometers with the capability to operate the helium device in a scalar mode. This special mode is used near the planet in order to determine with very high accuracy the interior field of the planet. The orbital mission will lead to

M. K. Dougherty; S. Kellock; D. J. Southwood; A. Balogh; E. J. Smith; B. T. Tsurutani; B. Gerlach; K.-H. Glassmeier; F. Gleim; C. T. Russell; G. Erdos; F. M. Neubauer; S. W. H. Cowley

2004-01-01

297

Magnetic Field Problem: Determining Current  

NSDL National Science Digital Library

A wire carrying an unknown current out of the page is shown above. You may also double-click in the animation to create a field line. Assume that the distance given is in cm and B is given in milli Tesla.

Christian, Wolfgang; Belloni, Mario

2007-03-03

298

Single conductor transmission cable magnetic fields  

SciTech Connect

Generally accepted methods for calculating magnetic fields in the vicinity of overhead transmission lines are currently available. These calculation procedures have received general acceptance because they are well documented and field measurements have verified their accuracy. Similar data and calculation procedures, however, are lacking for underground transmission cables. This report describes a research project which was designed to investigate the magnetic fields produced by single conductor underground transmission cables, specifically self-contained fluid filled and extruded dielectric types. A test bay was designed and constructed at the EPRI Waltz Mill Cable Test Facility to obtain measurements for a range of commonly used installation configurations, sheath grounding practices, load current magnitudes, and cable sheath constructions. The results of these tests showed that the magnetic field varies over a wide range depending on the cable installation configuration, sheath resistance and bonding, and the relationship of cable phases for double circuit installations. Magnetic field measurements were also conducted on an in-service single conductor transmission cable to substantiate and supplement the Waltz Mill test results. An analysis of the measured magnetic field values for both the Waltz Mill tests and the in-service transmission cable showed good agreement with currently existing calculation procedures. The calculation procedure which was used is similar to that for overhead transmission lines except that induced sheath/shield currents for multipoint sheath/shield grounding must be calculated and taken into account. The measurements showed that the earth has little or no effect on the above ground magnetic field. 7 refs., 23 figs., 11 tabs.

Cooper, J.H. (Power Technologies, Inc., Wilmerding, PA (United States))

1991-08-01

299

A Novel Method of Arraying Permanent Magnets Circumferentially to Generate a Rotation Magnetic Field  

Microsoft Academic Search

An outer magnetic field is extensively applied to drive the movement of a clinic micro-robot. However, how to produce a suitable magnetic field is a complicated problem. Commonly, the drive magnetic field is generated by a combination of power coils. This paper presents a novel method that circumferentially arrays identical permanent magnets to generate a rotational magnetic field in the

Wei Zhang; Yonggang Meng; Ping Huang

2008-01-01

300

Magnetic field gradients and their uses in the study of the earth's magnetic field  

Microsoft Academic Search

Magnetic field gradients are discussed from the standpoint of their usefulness in modeling crustal magnetizations. The fact that gradients enhance shorter wavelength features helps reduce both the core signal and the signal from external fields in comparison with the crustal signal. If the gradient device can be oriented, then directions of lineation can be determined from single profiles, and anomalies

C. G. A. Harrison; J. R. Southam

1991-01-01

301

MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS  

SciTech Connect

We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.

Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: aleko@tevza.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2012-11-01

302

Behavior of a Single Langmuir Probe in a Magnetic Field.  

ERIC Educational Resources Information Center

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

Pytlinski, J. T.; And Others

1978-01-01

303

Magnetic Field Effects on Plasma Plumes  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

304

Elliptical torii in a constant magnetic field  

E-print Network

The Schrodinger equation for an electron on the surface of an elliptical torus in the presence of a constant azimuthally symmetric magnetic field is developed. The single particle spectrum and eigenfunctions as a function of magnetic flux through the torus are determined and it is shown that inclusion of the geometric potential is necessary to recover the limiting cases of vertical strip and flat ring structures.

M. Encinosa; M. Jack

2005-09-23

305

Ferrofluid drops in rotating magnetic fields  

Microsoft Academic Search

Drops of a ferrofluid floating in a non-magnetic liquid of the same density and spun by a rotating magnetic field are investigated experimentally and theoretically. The parameters for the experiment are chosen such that different stationary drop shapes including non-axis-symmetric configurations could be observed. Within an approximate theoretical analysis the character of the occurring shape bifurcations, the different stationary drop

Alexander V. Lebedev; Andreas Engel; Konstantin I. Morozov; Heiko Bauke

2003-01-01

306

Cluster Magnetic Fields from Active Galactic Nuclei  

Microsoft Academic Search

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several

P. M. Sutter; P. M. Ricker; H.-Y. Yang

2009-01-01

307

Cluster magnetic fields from active galactic nuclei  

Microsoft Academic Search

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are\\u000aa possible source for weak cluster-wide magnetic fields. To evaluate this\\u000ascenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core\\u000acluster that include injection of kinetic, thermal, and magnetic energy via an\\u000aAGN-powered jet. Using the MHD solver in FLASH 2, we compare several

P. M. Sutter; P. M. Ricker; H.-Y. Yang

2009-01-01

308

High-? Injection into a Magnetic Mirror Field  

Microsoft Academic Search

Axial injection of a high-density helium plasma into a magnetic mirror has been experimentally studied. Observations of the plasma-field interaction were made with magnetic probes, electrostatic probes, piezoelectric probes, and an optical monochromator which analyzed emission-line profiles. In the central plane of the mirror a density of 2 1 1015 ions?cm3 and a maximum ion temperature of 10

F. R. Scott; O. C. Eldridge

1961-01-01

309

Radical Emissions and Butane Diffusion Flames Exposed to Uniform Magnetic Fields Encircled by Magnetic Gradient Fields  

Microsoft Academic Search

When butane diffusion flames were exposed to uniform magnetic fields encircled by magnetic gradient fields, emission intensities of such transitions as A2Sigma-->X2\\\\Pi of OH*, intensities of continuous spectra arising from the particle cloud radiation, and flame temperatures decreased, while flame dimensions increased. However, the changes in these quantities are very small compared with those for flames exposed to magnetic gradient

Takashi Aoki

1990-01-01

310

Fracture Intersection Waves: Theory and Experiment  

NASA Astrophysics Data System (ADS)

Fractures and fracture intersections are found nearly everywhere on earth and have also been observed on planetary surfaces within our solar system. The presence of fracture intersections adds complexity to the three-dimensional flow paths through rock and alters the scattered seismic wave field in a manner that does not occur for single fractures or parallel sets of fractures. A main challenge in working with intersecting fractures is how to determine the properties of intersections, whether intersections act as barriers to flow or as highly conductive paths. In this study, we determine theoretically and experimentally that the existence and velocity of intersection waves depends on the specific stiffness of the intersection which is stress dependent. It is well known that a single block supports a wedge wave along the corner or edge of a block. Conceptually, an intersection between two orthogonal fractures can be represented as four blocks coupled along their edges or as the coupling of four wedge waves. In this study, displacement discontinuity boundary conditions (discontinuity in displacement with continuity in stress) were used to represent the coupling among the blocks that form the fractures and the fracture intersection. Based on this approach, intersection waves were derived that are dispersive and range in velocity from a single wedge-mode to the bulk shear wave velocity. For low intersection stiffness, an intersection wave travels at the single wedge wave velocity because the intersection behaves as a free surface. As the intersection stiffness increases, the intersection wave velocity increases continuously to the Rayleigh velocity when two of the blocks forming the intersection are coupled. Finally, the intersection wave velocity increases continuously to the bulk shear wave velocity as coupling between all four blocks approaches the condition of a welded interface as the stiffness of the intersection and fractures increases. The velocity of the intersection waves depends on the relative stiffness between the two orthogonal fractures. Laboratory experiments were performed on an intersection between four aluminum blocks (0.29 m x 0.76 m x 0.76 m) as a function of stress. Piezoelectric contact transducers (1MHz) were used to propagate and measure intersection waves propagated along the intersection between the aluminum samples. Compressional and shear wave data were collected for samples subjected to bi-axial loading conditions used to close both the horizontal and vertical fracture planes individually. The measured waveforms verified that the velocity of the intersection wave did indeed range from the wedge velocity, at low applied loads, to the bulk velocity, when both fractures were under high load; indicating an agreement with the theoretical formulation for intersection waves. Intersection waves are a potential tool for characterizing the mechanical and hydraulic properties of fracture intersections because the velocity of these waves depends on the specific stiffness of the intersection. Acknowledgments: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022) and by the Geo-mathematical Imaging Group at Purdue University.

Abell, B.; Pyrak-Nolte, L. J.

2013-12-01

311

Observation of Magnetic Fields Generated by Tsunamis  

NASA Astrophysics Data System (ADS)

Tsunamis produce perturbations in the Earth's magnetic field by electromagnetic induction. Recent deployments of highly accurate magnetometers and the exceptionally deep solar minimum provided ideal conditions to observe these small signals from the tsunami resulting from the strong Chilean earthquake on 27 February 2010. Magnetic observatory measurements on Easter Island, 3500 kilometers west of the epicenter, show a periodic signal of 1 nanotesla, coincident in time with recordings from the local tide gauge. The detection of these magnetic signals represents a milestone in understanding tsunami-induced electromagnetic effects.

Manoj, Chandrasekharan; Maus, Stefan; Chulliat, Arnaud

2011-01-01

312

Secondary star magnetic fields in close binaries  

NASA Astrophysics Data System (ADS)

In this paper an attempt is made to use magnetic braking to constrain the surface polar field strengths of the secondary stars in close binaries with orbital periods between Porb ~ 3 and 7 h. By using a standard Mestel & Spruit model, assuming field saturation, a linear relation was obtained between the mass transfer and orbital period, for the period range under consideration, which allows constraining the surface polar field between B?,2 ~ 2900 and 3300 G. It has been shown that the predicted mass-transfer rates correlate with the Verbunt & Zwaan empirical mass transfer versus orbital period relation. Furthermore, it has been shown that the closed field lines, that is, the so-called dead zone, of the secondary star envelopes a substantial fraction of the binary, including the white dwarf, for all orbital periods under consideration. It has been shown that the interaction of the white dwarf field with the surrounding envelope can result in the intermediate polars entering the period gap being magnetically synchronized over time-scales ?syn <= 107yr. This mechanism may then play a significant role in the orbital evolution of the intermediate polars into the polars. Furthermore, surface magnetic field structures in the L1 region may play a significant role in the fragmentation of the mass flow near the L1 region, which may explain the inferred fragmented mass transfer, that is, the blobby mass flow, in magnetic cataclysmic variables.

Meintjes, P. J.; Jurua, E.

2006-11-01

313

Evolution of magnetic fields in stars across the upper main sequence: II. Observed distribution of the magnetic field geometry  

Microsoft Academic Search

We re-discuss the evolutionary state of upper main sequence magnetic stars using a sample of Ap and Bp stars with accurate Hipparcos parallaxes and definitely determined longitudinal magnetic fields. We confirm our previous results obtained from the study of Ap and Bp stars with accurate measurements of the mean magnetic field modulus and mean quadratic magnetic fields that magnetic stars

S. Hubrig; P. North; M. Schller

2007-01-01

314

Magnetic Field and Critical Current of a BSCCO HTS Magnet at Various Aspect Ratios  

Microsoft Academic Search

When the length of wire used to make an HTS magnet is fixed, the magnetic properties of the HTS magnet including the central magnetic field and stored energy mostly depend on the as- pect ratio of the HTS magnet. This paper presents calculations of the magnetic properties of a BSCCO HTS magnet at various as- pect ratios. The HTS magnet

Myunghun Kang; Youngmin Kim; Heejoon Lee; Gueesoo Cha; Kyungwoo Ryu

2011-01-01

315

Enhanced Cloud Disruption by Magnetic Field Interaction  

NASA Astrophysics Data System (ADS)

We present results from the first three-dimensional numerical simulations of moderately supersonic cloud motion through a tenuous, magnetized medium. We show that the interaction of the cloud with a magnetic field perpendicular to its motion has a great dynamical impact on the development of instabilities at the cloud surface. Even for initially spherical clouds, magnetic field lines become trapped in surface deformations and undergo stretching. The consequent field amplification that occurs there and, in particular, its variation across the cloud face then dramatically enhance the growth rate of Rayleigh-Taylor unstable modes, hastening the cloud disruption. Animations and color images from this work have been posted at http://www.msi.umn.edu/Projects/twj/mhd3d/.

Gregori, G.; Miniati, Francesco; Ryu, Dongsu; Jones, T. W.

1999-12-01

316

Magnetic field draping about coronal mass ejecta  

SciTech Connect

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

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

1987-01-01

317

Orbital mapping of the lunar magnetic field.  

NASA Technical Reports Server (NTRS)

Examination of the lunar magnetic field as deduced from the orbital magnetometer data, with major emphasis on the general mapping of the lunar field over the orbit track of the Apollo 15 subsatellite. A detailed analysis of the data from a series of overflights of the Van de Graaff region at two different altitudes is also presented. This latter set of data makes it possible to determine the scale size of the region and the contrast between the remanent magnetization associated with the magnetic feature and its surroundings. The low altitude data from the Apollo 16 subsatellite, just prior to its impact into the lunar surface, are then examined. Data obtained while the moon was in the solar wind are used to construct a map which shows the lunar limb regions associated with the detection of limb compressions. This map is used to make qualitative inferences concerning the lunar remanent field in regions not covered by the contour maps.

Sharp, L. R.; Coleman, P. J., Jr.; Lichtenstein, B. R.; Russell, C. T.; Schubert, G.

1973-01-01

318

Configuration of the local interstellar magnetic field  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

319

Bound states in a strong magnetic field  

SciTech Connect

We expect a strong magnetic field to be produced in the perpendicular direction to the reaction plane, in a noncentral heavy-ion collision . The strength of the magnetic field is estimated to be eB{approx}m{sup 2}{sub {pi}}{approx} 0.02 GeV{sup 2} at the RHIC and eB{approx} 15m{sup 2}{sub {pi}}{approx} 0.3 GeV{sup 2} at the LHC. We investigate the effects of the magnetic field on B{sup 0} and D{sup 0} mesons, focusing on the changes of the energy levels and of the mass of the bound states.

Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G. [Instituto de Fisica, Universidade de Sao Paulo Rua do Matao, Travessa R, 187, 05508-090 Sao Paulo, SP (Brazil); Ferreira Filho, L. G. [Departamento de Matematica e Computacao, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro Rodovia Presidente Dutra, km 298, Polo Industrial, CEP 27537-000, Resende, RJ (Brazil)

2013-03-25

320

Magnetic Fields in Post-AGB Stars  

NASA Astrophysics Data System (ADS)

Between the AGB and the Planetary Nebula phase we observe an evolution in the shaping of some stars: from a spherical symmetry they become elliptical, bipolar, or even quadripolar. The shaping of late-type stars is still not well understood and several theories are suggested. Among them is the action of magnetic fields, which have been detected in AGB stars via maser measurements and also measured in the central stars of some PNe. We present here new submillimeter (450 and 850 ?m) polarimetric data, obtained with SCUBA at the JCMT, for four bipolar post-AGBs and PNe: NGC 6537, NGC 7027, NGC 6302 and CRL 2688. The geometry of the magnetic field is determined by dust alignment. These new data will allow us to better understand the role played by magnetic fields not only in post-AGBs but also in AGBs where departures from sphericity have been observed.

Sabin, L.; Zijlstra, A. A.; Greaves, J. S.

2007-11-01

321

Is there a maximum magnetic field in QED?  

NASA Astrophysics Data System (ADS)

It was recently conjectured by Shabad and Usov that there exists in QED a maximum magnetic field of 10 G, above which the magnetized vacuum becomes unstable. Using a nonperturbative analysis that consistently incorporates the effective electron mass and the screening effect in a strong magnetic field, we show that the conjectured phenomenon of positronium collapse never takes place. Thus, there does not exist a maximum magnetic field in QED and the magnetized vacuum is stable for all values of the magnetic field.

Leung, Chung Ngoc; Wang, Shang-Yung

2009-04-01

322

Magnetic translation algebra with or without magnetic field  

NASA Astrophysics Data System (ADS)

The magnetic translation algebra plays an important role in the quantum Hall effect. Murthy and Shankar have shown how to realize this algebra using fermionic bilinears defined on a two-dimensional square lattice. We show that, in any dimension d, it is always possible to close the magnetic translation algebra using fermionic bilinears, be it in the continuum or on the lattice. We also show that these generators are complete in even, but not odd, dimensions, in the sense that any fermionic Hamiltonian in even dimensions that conserves particle number can be represented in terms of the generators of this algebra, whether or not time-reversal symmetry is broken. As an example, we reproduce the f-sum rule of interacting electrons at vanishing magnetic field using this representation. We also show that interactions can significantly change the bare band width of lattice Hamiltonians when represented in terms of the generators of the magnetic translation algebra.

Mudry, Christopher; Chamon, Claudio

2013-03-01

323

Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature  

NASA Technical Reports Server (NTRS)

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

Parkin, C. W.

1978-01-01

324

Dynamics of Solar Magnetic Fields: Theoretical Aspects  

NASA Astrophysics Data System (ADS)

The distribution of magnetic fields on the solar surface is determined by processes of flux emergence, transport and cancellation. Magnetic flux emerges in the form of bipoles of various size, strength and orientation. Large and medium-sized active regions emerge in two activity belts on either side of the equator, and generally have orientations in accordance with Hale's polarity law. Smaller ephemeral regions have a broader latitude distribution and a more random orientation. Weak intranetwork fields are seen to emerge in the centers of supergranules everywhere on the Sun. The emerged field interacts with convective flows on a variety of spatial and temporal scales, creating a continually evolving pattern of small-scale flux concentrations and causing the magnetic elements to perform a random walk across the solar surface. Chance encounters of opposite polarity elements can lead to flux cancellation, i.e. disappearance of magnetic flux from the photosphere. In this talk I review recent developments in the theory and modelling of these physical processes. The emphasis is on the structure and dynamics of magnetic fields in the photosphere and below. I conclude with a list of key scientific questions to be addressed by future research.

van Ballegooijen, A. A.

1996-05-01

325

Effect of magnetic field on the wave dispersion relation in three-dimensional dusty plasma crystals  

SciTech Connect

Three-dimensional plasma crystals under microgravity condition are investigated by taking into account an external magnetic field. The wave dispersion relations of dust lattice modes in the body centered cubic (bcc) and the face centered cubic (fcc) plasma crystals are obtained explicitly when the magnetic field is perpendicular to the wave motion. The wave dispersion relations of dust lattice modes in the bcc and fcc plasma crystals are calculated numerically when the magnetic field is in an arbitrary direction. The numerical results show that one longitudinal mode and two transverse modes are coupled due to the Lorentz force in the magnetic field. Moreover, three wave modes, i.e., the high frequency phonon mode, the low frequency phonon mode, and the optical mode, are obtained. The optical mode and at least one phonon mode are hybrid modes. When the magnetic field is neither parallel nor perpendicular to the primitive wave motion, all the three wave modes are hybrid modes and do not have any intersection points. It is also found that with increasing the magnetic field strength, the frequency of the optical mode increases and has a cutoff at the cyclotron frequency of the dust particles in the limit of long wavelength, and the mode mixings for both the optical mode and the high frequency phonon mode increase. The acoustic velocity of the low frequency phonon mode is zero. In addition, the acoustic velocity of the high frequency phonon mode depends on the angle of the magnetic field and the wave motion but does not depend on the magnetic field strength.

Yang Xuefeng [School of Mathematical Sciences, Dalian University of Technology, Dalian 116024 (China); Wang Zhengxiong [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China)

2012-07-15

326

The Intersection Challenge  

ERIC Educational Resources Information Center

Street intersections are a source of accidents--for both automobiles and pedestrians. This article presents an intersection challenge that allows students to explore some possible ways to change the traditional intersection. In this challenge, teachers open up the boundaries and allow students to redesign their world. The first step is to help

Roman, Harry T.

2011-01-01

327

The Magnetic Field in the Outer Heliosphere  

NASA Technical Reports Server (NTRS)

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

Suess, S. T.

2004-01-01

328

Magnetic fields of HgMn stars?  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

329

Interpretation of Solar Magnetic Field Strength Observations  

E-print Network

This study based on longitudinal Zeeman effect magnetograms and spectral line scans investigates the dependence of solar surface magnetic fields on the spectral line used and the way the line is sampled in order to estimate the magnetic flux emerging above the solar atmosphere and penetrating to the corona from magnetograms of the Mt. Wilson 150-foot tower synoptic program (MWO). We have compared the synoptic program \\lambda5250\\AA line of Fe I to the line of Fe I at \\lambda5233\\AA since this latter line has a broad shape with a profile that is nearly linear over a large portion of its wings. The present study uses five pairs of sampling points on the $\\lambda5233$\\AA line. We recommend adoption of the field determined with a line bisector method with a sampling point as close as possible to the line core as the best estimate of the emergent photospheric flux. The combination of the line profile measurements and the cross-correlation of fields measured simultaneously with \\lambda5250\\AA and \\lambda5233\\AA yields a formula for the scale factor 1/\\delta that multiplies the MWO synoptic magnetic fields. The new calibration shows that magnetic fields measured by the MDI system on the SOHO spacecraft are equal to 0.619+/-0.018 times the true value at a center-to-limb position 30 deg. Berger and Lites (2003) found this factor to be 0.64+/-0.013 based on a comparison the the Advanced Stokes Polarimeter.

R. K. Ulrich; L. Bertello; J. E. Boyden; L. Webster

2008-12-12

330

The National High Magnetic Field Laboratory  

NASA Astrophysics Data System (ADS)

The National High Magnetic Field Laboratory (NHMFL) is a collaboration between Florida State University, the University of Florida, and the Los Alamos National Laboratory. The DC Field Facilities are located at the main campus for the NHMFL in Tallahassee, Florida and are described in this paper. The DC Field Facility has a variety of resistive and superconducting magnets. The DC Field Facility infrastructure, the most powerful in the world, is able to provide 57 MW of continuous low noise DC power. Constant magnetic fields of up to 45 tesla in a 32 mm bore and 20 tesla in 195 mm bore are available at no charge to the user community. The users of the facility are selected by a peer reviewed process. Roughly 400 research groups visit the lab to conduct experiments each year. Experimental capabilities provided by the NHMFL are magneto-optics, millimeter wave spectroscopy, magnetization, dilatometry, specific heat, electrical transport, ultrasound, low to medium resolution NMR, EMR, and materials processing. Measurements of properties can be made on samples at temperatures from 20 mK to 1000 K, pressures from ambient to 10 GPa, orientation and currents from 1 pA to 10 kA.

Hannahs, S. T.; Palm, E. C.

2010-04-01

331

Tracing the Magnetic Field in Orion A  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

332

Multi-Coil Magnetic Field Modeling  

PubMed Central

The performance of multi-coil (MC) magnetic field modeling is compared to dedicated wire patterns for the generation of spherical harmonic (SH) shapes as these are the workhorse for spatial encoding and magnetic field homogenization in MR imaging and spectroscopy. To this end, an example 48 channel MC setup is analyzed and shown to be capable of generating all first through fourth order SH shapes over small and large regions-of-interest relevant for MR investigations. The MC efficiency for the generation of linear gradient fields shares the same order of magnitude with classic and state-of-the-art SH gradient coils. MC field modeling becomes progressively more efficient with the synthesis of more complex field shapes that require the combination of multiple SH terms. The possibility of a region-specific optimization of both magnetic field shapes and generation performance with the MC approach are discussed with emphasis on the possible trade-off between the field accuracy and generation efficiency. MC shimming has been shown previously to outperform current SH shimming. Along with the efficiency gains of MC shimming shown here, the MC concept has the potential to 1) replace conventional shim systems that are based on sets of dedicated SH coils and 2) allow optimal object-specific shim solutions similar to object-specific RF coils. PMID:24095841

Juchem, Christoph; Green, Dan; de Graaf, Robin A.

2013-01-01

333

Biomaterials and Magnetic fields for Cancer Therapy  

NASA Technical Reports Server (NTRS)

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

Ramachandran, Narayanan; Mazuruk, Konstanty

2003-01-01

334

Sensor for detecting changes in magnetic fields  

DOEpatents

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

Praeg, W.F.

1980-02-26

335

Sensor for detecting changes in magnetic fields  

DOEpatents

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

Praeg, Walter F. (Palos Park, IL)

1981-01-01

336

High magnetic field facilities in Latin America  

NASA Astrophysics Data System (ADS)

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

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

2006-11-01

337

Magnetic field and gradient analysis around matrix for HGMS  

NASA Astrophysics Data System (ADS)

A High Gradient Magnetic Separator (HGMS) uses matrix to make high magnetic field gradient so that ferro- or para-magnetic particles can be attracted to them by high magnetic force. These matrixes are usually composed of stainless wires having high magnetization characteristics. This paper deals with superconducting HGMS which is aimed for purifying wastewater by using stainless steel matrix. Background magnetic field up to 6 T is generated by a superconducting solenoid and the stainless steel matrix are arranged inside of the solenoid. In order to calculate magnetic forces exerting on magnetic particles in wastewater, it is important to calculate magnetic field and magnetic field gradient those are proportional to the magnetic force acting on the particle. So we presents magnetic field distribution analysis result and estimates how many times of magnetic force will act on a particle when the matrix are arranged or not.

Baik, S. K.; Ha, D. W.; Ko, R. K.; Kwon, J. M.

2010-11-01

338

Cluster Magnetic Fields from Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.

Sutter, P. M.; Ricker, P. M.; Yang, H.-Y.

2009-12-01

339

Cluster magnetic fields from active galactic nuclei  

E-print Network

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.

Sutter, P M; Yang, H -Y

2009-01-01

340

The mechanisms of the effects of magnetic fields on cells  

Microsoft Academic Search

The evolution of organisms in conditions of the Earth magnetism results in close dependence of their functioning on the properties of the Earth magnetic field. The magnetic conditions in space flight differ from those on the Earth (e.g. much smaller values of magnetic filed) that effect various processes in living organisms. Meanwhile the mechanisms of interaction of magnetic fields with

A. Kondrachuk

2002-01-01

341

Magnetic stray fields of periodically arranged Co-Crmicro strips  

Microsoft Academic Search

Research was carried out on magnetic stray fields of Co-Cr micro strips. This investigation was motivated by the search for increasing bit density and miniaturisation in magnetic data storage and magnetic sensor devices. In these devices the magnetisation is patterned, i.e. by writing bits or etching micro structures in a magnetic material. As a result magnetic stray fields exist outside

J. G. T. te Lintelo

1993-01-01

342

Structural alloys for high field superconducting magnets  

SciTech Connect

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

Morris, J.W. Jr.

1985-08-01

343

Magnetic properties and microstructure of bulk Nd-Fe-B magnets solidified in magnetic field  

NASA Astrophysics Data System (ADS)

The Nd-Fe-B bulk magnets with a slab shape of 0.9 4 15 mm3 were prepared by injection casting into a copper mold. The effects of applying a magnetic field during the casting process on the magnetic properties and microstructure of Nd9.5Fe71.5Ti2.5Zr0.5Cr1B14.5C0.5 alloy have been studied. The results show that the sample cast with magnetic field has a stronger (00L) texture of Nd2Fe14B phase with the c-axis perpendicular to the slab plane than the sample cast without magnetic field. The intensity of the texture weakens from surface to inner region of the bulk magnets. Applying a magnetic field during the casting process is helpful to refine the grain size effectively. As a result, the magnetic properties are improved from Br = 5.8 kG, iHc = 6.5 kOe, and (BH)max = 5.9 MGOe for thesample cast without magnetic field to Br = 6.1 kG, iHc = 10.3 kOe, and (BH)max = 7.3 MGOe for the sample cast with a 3.7 kOe magnetic field.

Wang, C.; Lai, Y. S.; Hsieh, C. C.; Chang, W. C.; Chang, H. W.; Sun, A. C.

2011-04-01

344

Dynamic evolution of coronal magnetic fields  

NASA Technical Reports Server (NTRS)

The response of coronal magnetic fields to photospheric motion is investigated using a time-dependent, two-dimensional MHD simulation. Starting with an initially uniform field, a circular section of the loop base is slowly rotated to represent the photospheric motion. The field lines at the base move with this flow in a manner consistent with the generated electric fields. The subsequent evolution of the field and flow can be characterized as passing through several distinct configurations. In the earliest phase the kinetic energy is negligible, and the current and field are parallel throughout most of the cylinder. This is followed by a period in which the field rotation increases, the axial field at and near the axis increases, and the acial field decreases in two cylindrical regions away from the axis. When the field in an appreciable portion of the cylinder has undergone one complete rotation, a rapid change in field configuration occurs with a large portion of the field making several rotations at large radii and a corresponding large reduction in the axial field.

Steinolfson, Richard S.

1986-01-01

345

Modeling maglev passenger compartment static magnetic fields from linear Halbach permanent-magnet arrays  

Microsoft Academic Search

Passenger compartment magnetic field levels in a low-speed magnetic levitation (maglev) vehicle that uses linear Halbach permanent-magnet arrays for both levitation and propulsion are computed through superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. End effects due to the finite lengths of the arrays lead to fields that decay much less rapidly

James F. Hoburg

2004-01-01

346

Resolution of direction of oceanic magnetic lineations by the sixth-generation lithospheric magnetic field  

E-print Network

of the magnetic field caused by the magnetization of the Earth's lithosphere. A com- prehensive overview magnetic field model from CHAMP satellite magnetic measurements S. Maus CIRES, University of Colorado [1] The CHAMP satellite continues to provide highly accurate magnetic field measurements from

Müller, Dietmar

347

Survey of residential magnetic field sources  

Microsoft Academic Search

A nationwide survey of 1000 residences is underway to determine the sources and characteristics of magnetic fields in the home. This report describes the goals, statistical sampling methods, measurement protocols, and experiences in measuring the first 707 residences of the survey. Some preliminary analysis of the data is also included. Investigators designed a sampling method to randomly select the participating

Zaffanella

1992-01-01

348

The Earth's magnetic field: Which geometry?  

Microsoft Academic Search

Were it not for the presence of a solar wind, the intrinsic magnetic field of the Earth---if observed from far enough out in space---would appear to be almost perfectly dipolar, with the axis of the dipole presently tilted by some 10 with respect to the rotation axis. At the Earth's surface, the axial dipolar term is dominant, which serves among

Vincent Courtillot; Jean-Pierre Valet; Gauthier Hulot; Jean-Louis Le Moul

1992-01-01

349

A dynamo model of Jupiter's magnetic field  

NASA Astrophysics Data System (ADS)

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

Jones, C. A.

2014-10-01

350

PROTONS IN THE EARTH'S MAGNETIC FIELD  

Microsoft Academic Search

The identity, flux, and energy distribution of particles trapped in the ; earth's magnetic field were determined for those particles which penetrate more ; than 6 g\\/cm² of material. Nuclear emulsions exposed to the Van Allen ; radiation belt by a Thor-Able ballistic missile were used in the measurements. ; The separation of protons and electrons was done unambiguously for

R. S. White

1959-01-01

351

Photoneutrino energy loss rates under magnetic field  

Microsoft Academic Search

The neutrino energy loss rate is calculated due to the photoneutrino process in a hot plasma, under magnetic field.\\u000a \\u000a The calculations done for low densities and relatively low temperatures may be used for astrophysical estimations in neutron\\u000a stars.

M. El-Khishen; A. El-Gowhari; M. Toubia

1975-01-01

352

Electron-positron annihilation under magnetic field  

Microsoft Academic Search

The radiation loss due to the annihilation of electron-positron pair into two ?-quanta in neutron stars is calculated. The\\u000a dependence of radiation loss on the magnetic field, density, temperature, and chemical potentials is explicitly shown for\\u000a relativistic and non-relativistic cases. The reaction cross section is also calculated.

M. El Khishen; M. Toubia

1976-01-01

353

Magnetic Fields Near Mars - First Results  

Microsoft Academic Search

The magnetic fields of Mars have been measured from Phobos 2 with high temporal resolution in the tail and down to an 850-km altitude. During four successive highly elliptical orbits, the position of the bow shock as well as that of a transition layer, the 'planetopause', were identified. Subsequent circular orbits at 6000-km altitude provided the first high-resolution data in

H. Michaelis; K. Schwingenschuh; D. Moehlmann; V. N. Oraevskii; E. Eroshenko; J. Kurths; D. Lenners; J. Linthe; V. Kobzev; V. Styashkin; J. Achache; J. Slavin; J. G. Luhmann; C. T. Russell; H. Arnold; T. Raditsch; U. Auster; K.-H. Fornacon; H. J. Schenk; U. Motschmann; T. Roatsch; K. Sauer; R. Schrter

1989-01-01

354

Starspots Magnetic field by transit mapping  

NASA Astrophysics Data System (ADS)

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

Vlio, Adriana; Spagiari, Eduardo

2014-08-01

355

The GGS\\/POLAR magnetic fields investigation  

Microsoft Academic Search

The magnetometer on the POLAR Spacecraft is a high precision instrument designed to measure the magnetic fields at both high and low altitudes in the polar magnetosphere in 3 ranges of 700, 5700, and 47000 nT. This instrument will be used to investigate the behavior of fieldaligned current systems and the role they play in the acceleration of particles, and

C. T. Russell; R. C. Snare; J. D. Means; D. Pierce; D. Dearborn; M. Larson; G. Barr; G. Le

1995-01-01

356

Passive levitation in alternating magnetic fields  

DOEpatents

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

Romero, Louis (Albuquerque, NM); Christenson, Todd (Albuquerque, NM); Aronson, Eugene A. (Albuquerque, NM)

2010-09-14

357

CMB polarization induced by stochastic magnetic fields  

E-print Network

The complete calculation of the CMB polarization observables (i.e. E- and B-modes) is reported within the conventional $\\Lambda$CDM paradigm supplemented by a stochastic magnetic field. Intriguing perspectives for present and forthcoming CMB polarization experiments are outlined.

Massimo Giovannini; Kerstin E. Kunze

2008-04-14

358

The main magnetic field of Jupiter  

Microsoft Academic Search

The main magnetic field of Jupiter has been measured by the Goddard Space Flight Center flux gate magnetometer on Pioneer 11, and analysis of the data yields a more detailed model than that obtained from Pioneer 10 results. In a spherical harmonic octupole representation the dipole term (with opposite polarity to earth's) has a magnitude of 4.28 G R\\/sub j\\/

Mario H. Acuna; Norman F. Ness

1976-01-01

359

Weakly bound electrons in external magnetic field  

E-print Network

The effect of the uniform magnetic field on the electron in the spherically symmetric square-well potential is studied. A transcendental equation that determines the electron energy spectrum is derived. The approximate value of the lowest (bound) energy state is found. The approximate wave function and probability current density of this state are constructed.

I. V. Mamsurov; F. Kh. Chibirova

2007-03-07

360

Strain sensors for high field pulse magnets  

SciTech Connect

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

Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

2009-01-01

361

The main magnetic field of Jupiter  

Microsoft Academic Search

The main magnetic field of Jupiter has been measured by the Goddard Space Flight Center flux gate magnetometer on Pioneer 11. Analysis of the data yields a more detailed model than that obtained from Pioneer 10 results. In a spherical harmonic octupole representation the dipole term (with opposite polarity to earth's) has a magnitude of 4.28 G times the radial

M. H. Acuna; N. F. Ness

1976-01-01

362

Reducing Magnetic Fields Around Power Cables  

NASA Technical Reports Server (NTRS)

Four power conductors arranged symmetrically about fifth grounded conductor. Four current-carrying wires arranged symmetrically around central grounded wire that nominally carries no current. In comparison with other cable configurations, this one results in smaller magnetic fields around cable. Technique for use when size of wires in cable makes twisting impractical.

Sargent, Noel B.; Gitelman, Florida; Pongracz-Bartha, Edward; Spalding, John

1993-01-01

363

Cylindrical isentropic compression by ultrahigh magnetic field  

NASA Astrophysics Data System (ADS)

The cylindrical isentropic compression by ultrahigh magnetic field (MC-1) is a kind of unique high energy density technique. It has characters like ultrahigh pressure and low temperature rising, and would have widely used in areas like high pressure physics, new material synthesis and ultrahigh magnetic field physics. The Institute of Fluid Physics, Chinese Academy of Engineering Physics (IFP, CAEP) has begun the experiment since 2011 and a primary experimental device had been set-up. In the experiments, a seed magnetic field of 5 Tesla were set-up first and compressed by a stainless steel liner which is driven by high explosive initiated synchronously. The internal diameter of the liner is 97 mm, and its thickness is 1.5 mm. The movement of liner was recorded optically and a typical turnaround phenomenon was observed. From the photography results the liner was compressed smoothly and evenly and its average velocity was about 5-6 km/s. In the experiment a axial magnetic field of over 1400 Tesla has been recorded. The MC-1 process was numerical simulated by 1D MHD code MC11D and the simulations are in accord with the experiments.

Gu, Zhuowei; Luo, Hao; Zhang, Hengdi; Zhao, Shichao; Tang, Xiaosong; Tong, Yanjin; Song, Zhenfei; Tan, Fuli; Zhao, Jianheng; Sun, Chengwei

2014-05-01

364

Latitudinal dependence of the interplanetary magnetic field spectrum  

Microsoft Academic Search

Magnetic field data of Helios 1 in 1975 and Helios 2 in 1976 have been used to investigate the dependence of the interplanetary magnetic field power spectrum upon the angular displacement from the magnetic equator. At low wave numbers the magnetic field convected by the slow solar wind (associated to low latitudes) has spectral signatures different from those of the

R. Bruno; B. Bavassano

1987-01-01

365

The National High Magnetic Field Laboratory . . . . . . . . Pre Outreach Activity . . . . . . . . . . . . . . . . . . . . . . . . . . .  

E-print Network

#12;2 Table of Contents The National High Magnetic Field Laboratory . . . . . . . . Overview Pre? · The National High Magnetic Field Laboratory is a working science research laboratory utilizing state-of-the-art high magnetic field research systems. It is a world leader in magnet-related research and technology

Weston, Ken

366

In situ magnetic field observations of the AMPTE artificial comet  

NASA Technical Reports Server (NTRS)

Magnetometers aboard the IRM and UKS spacecraft monitored the magnetic field during the AMPTE artificial comet experiment of Dec. 27, 1984. Rapid photoionization of the released barium vapor resulted in the formation of a magnetic cavity, shielded from the ambient magnetic field.The presence of this highly conductive obstacle caused draping and compression of the solar wind magnetic field.

Luehr, H.; Kloecker, N.; Southwood, D. J.; Dunlop, M. W.; Mier-Jedrzejowicz, W. A. C.; Rijnbeek, R. P.; Six, M.; Haeusler, B.; Acuna, M.

1986-01-01

367

NOTICE: This paper, Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism, contains an error in the characteristic 2 case. A copy of the Corrigendum  

E-print Network

NOTICE: This paper, Intersection homology with field coefficients: K-Witt spaces and K-Witt bordism, contains an error in the characteristic 2 case. A copy of the Corrigendum and follow-up work in K-Witt homology with field coefficients: K-Witt spaces and K-Witt bordism Greg Friedman Texas Christian University

Friedman, Greg

368

Magnetic Fields In Relativistic Collisionless Shocks  

NASA Astrophysics Data System (ADS)

We present a systematic study on magnetic fields in Gamma-Ray Burst (GRB) relativistic shocks by making use of X-ray and optical afterglow observations, mostly coming from the Swift satellite. We use two methods to constrain the afterglow parameter epsilon_B (the fraction of energy in the magnetic field in the shocked plasma): 1. For the X-ray sample, the observed flux at the end of the X-ray steep decline is larger than or equal to the flux from the external-forward shock. 2. The observed optical afterglow flux arises from the external-forward shock emission. From the method for our X-ray sample (60 GRBs), we determine an upper limit on epsilon_B and from the method for our optical sample (35 GRBs), we determine a measurement for epsilon_B. Combining our X-ray and optical results, the median value we found for epsilon_B is ~ 10^-5. The distributions of epsilon_B from our X-ray and optical samples showed a wide distribution, with epsilon_B ranging from ~ 10^-7 - 10^-3. To characterize how much magnetic field amplification is needed, beyond shock compression of the seed magnetic field, we expressed our results for epsilon_B in terms of an amplification factor, AF. For both our X-ray and optical samples, the median value we found is AF 50-70. The distributions of AF from our X-ray and optical samples also showed a wide distribution, with AF ranging from ~ 1-1000. These results for epsilon_B and AF suggest that a weak amplification, in addition to shock compression, is needed to explain the afterglow observations. Our main conclusion is that shock compression and weak amplification of the magnetic field in GRB relativistic external shocks is sufficient to explain the afterglow data.

Santana, Rodolfo; Barniol Duran, R.; Kumar, P.

2013-01-01

369

Circular polarization of obliquely propagating whistler wave magnetic field  

SciTech Connect

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

Bellan, P. M. [Applied Physics, Caltech, Pasadena California 91125 (United States)] [Applied Physics, Caltech, Pasadena California 91125 (United States)

2013-08-15

370

Absolute magnetic helicity and the cylindrical magnetic field  

SciTech Connect

The different magnetic helicities conserved under conditions of perfect electrical conductivity are expressions of the fundamental property that every evolving fluid surface conserves its net magnetic flux. This basic hydromagnetic point unifies the well known Eulerian helicities with the Lagrangian helicity defined by the conserved fluxes frozen into a prescribed set of disjoint toroidal tubes of fluid flowing as a permanent partition of the entire fluid [B. C. Low, Astrophys. J. 649, 1064 (2006)]. This unifying theory is constructed from first principles, beginning with an analysis of the Eulerian and Lagrangian descriptions of fluids, separating the ideas of fluid and magnetic-flux tubes and removing the complication of the magnetic vector potential's free gauge from the concept of helicity. The analysis prepares for the construction of a conserved Eulerian helicity, without that gauge complication, to describe a 3D anchored flux in an upright cylindrical domain, this helicity called absolute to distinguish it from the well known relative helicity. In a version of the Chandrasekhar-Kendall representation, the evolving field at any instant is a unique superposition of a writhed, untwisted axial flux with a circulating flux of field lines all closed and unlinked within the cylindrical domain. The absolute helicity is then a flux-weighted sum of the writhe of that axial flux and its mutual linkage with the circulating flux. The absolute helicity is also conserved if the frozen-in field and its domain are continuously deformed by changing the separation between the rigid cylinder-ends with no change of cylinder radius. This hitherto intractable cylindrical construction closes a crucial conceptual gap for the fundamentals to be complete at last. The concluding discussion shows the impact of this development on our understanding of helicity, covering (i) the helicities of wholly contained and anchored fields; (ii) the Eulerian and Lagrangian descriptions of field evolution; (iii) twist as a topological property of solenoidal fields versus the linkage properties of open and closed discrete curves treated by Gauss, Caligarneau, Berger, and Prior; and (iv) the change of absolute helicity by resistive diffusion. These are important hydromagnetic properties of twisted magnetic fields in the million-degree hot, highly conducting corona of the Sun.

Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)

2011-05-15

371

Dynamic nuclear polarization at high magnetic fields  

PubMed Central

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

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

2009-01-01

372

Magnetic field contribution to the Lorentz model.  

PubMed

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

Oughstun, Kurt E; Albanese, Richard A

2006-07-01

373

The ESRF Miniature Pulsed Magnetic Field System  

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

374

The ESRF Miniature Pulsed Magnetic Field System  

SciTech Connect

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

Linden, Peter J. E. M. van der; Strohm, Cornelius; Roth, Thomas; Detlefs, Carsten; Mathon, Olivier [ESRF, 6 rue Jules Horowitz, F-38043 Grenoble (France)

2010-06-23

375

Warm Magnetic Field Measurements of LARP HQ Magnet  

SciTech Connect

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

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

2011-03-28

376

Magnetic-Field-Tunable Superconducting Rectifier  

NASA Technical Reports Server (NTRS)

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

Sadleir, John E.

2009-01-01

377

Hall Magnetic Reconnection: Guide Field Dependence  

NASA Astrophysics Data System (ADS)

Two (2D) and three (3D) dimensional Hall magnetohydrodynamic (MHD) simulations are used to study the dependence of a guide field on magnetic reconnection. The 2D simulations are run until a steady state is achieved for B gf/B0 = 0, 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 where B gf is the guide field and B0 is the reversed field. It is found that the reconnection rate and plasma energization are reduced for increasing guide field strength. This is caused by a J B force associated with Hall currents and the guide field that reduce the inflow and outflow velocities. However, the reconnection rate and plasma energization are only reduced by a factor of 2 for B gf = 5 B0. Additionally, the quadrupole field associated with Hall reconnection is eliminated for B gf ? B0/3. The 3D simulations demonstrate asymmetric development of a reconnection line [similar to the no guide field case reported by Huba and Rudakov (2002)], as well as the development of a (braided) magnetic flux tube. Applications to magnetospheric plasmas are discussed. Huba, J.D. and L.I. Rudakov, Phys. Plasmas 9, 4435 (2002). Research supported by NASA and ONR.

Rudakov, L.; Huba, J.

2004-12-01

378

Sunspots with the Strongest Magnetic Fields  

NASA Astrophysics Data System (ADS)

The strongest observed solar magnetic fields are found in sunspot umbrae and associated light bridges. We investigate systematic measurements of approximately 32 000 sunspot groups observed from 1917 through 2004 using data from Mt. Wilson, Potsdam, Rome and Crimea observatories. Isolated observations from other observatories are also included. Corrections to Mt. Wilson measurements are required and applied. We found 55 groups (0.2%) with at least one sunspot with one magnetic field measurement of at least 4000 G including five measurements of at least 5000 G and one spot with a record field of 6100 G. Although typical strong-field spots are large and show complex structure in white light, others are simple in form. Sometimes the strongest fields are in light bridges that separate opposite polarity umbras. The distribution of strongest measured fields above 3 kG appears to be continuous, following a steep power law with exponent about -9.5. The observed upper limit of 5 6 kG is consistent with the idea that an umbral field has a more or less coherent structure down to some depth and then fragments. We find that odd-numbered sunspot cycles usually contain about 30% more total sunspot groups but 60% fewer >3 kG spots than preceding even-numbered cycles.

Livingston, W.; Harvey, J. W.; Malanushenko, O. V.; Webster, L.

2006-12-01

379

Particle propagation in the solar wind: Anomalous diffusion of magnetic field lines in turbulent magnetic fields  

Microsoft Academic Search

In order to predict the entry of energetic particles of solar origin into the Earth's magnetosphere, it is necessary to understand how these particles propagate in the solar wind. The random walk of magnetic field lines is studied numerically in the case that a spectrum of magnetic fluctuations is present. In particular, the anisotropic turbulence typical of the solar wind

P. Veltri; G. Zimbardo; P. Pommois

1998-01-01

380

Crustal Magnetic Field Anomalies and Global Tectonics  

NASA Astrophysics Data System (ADS)

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

Storetvedt, Karsten

2014-05-01

381

Detecting solar axions using Earth's magnetic field  

E-print Network

We show that solar axion conversion to photons in the Earth's magnetosphere can produce an x-ray flux, with average energy \\sim 4 keV, which is measurable on the dark side of the Earth. The smallness of the Earth's magnetic field is compensated by a large magnetized volume. For axion masses Earth-orbit x-ray detector with an effective area of 10^4 cm^2, pointed at the solar core, can probe the photon-axion coupling down to 10^{-11} GeV^{-1}, in one year. Thus, the sensitivity of this new approach will be an order of magnitude beyond current laboratory limits.

Hooman Davoudiasl; Patrick Huber

2005-09-26

382

Neutrino propagation in a random magnetic field  

SciTech Connect

The active-sterile neutrino conversion probability is calculated for a neutrino propagating in a medium in the presence of random magnetic field fluctuations. A necessary condition for the probability to be positive definite is obtained for active-sterile electron neutrino conversion in the early universe hot plasma and in a supernova. The neutrino magnetic moment obtained from the positive definiteness of the conversion probability defines the range of validity of our approximation, rather than putting any physical bound on it. {copyright} {ital 1997} {ital The American Physical Society}

Sahu, S. [Theory Group, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009 (India)] [Theory Group, Physical Research Laboratory, Navrangpura, Ahmedabad-380 009 (India)

1997-10-01

383

Orientation and Magnitude of Mars' Magnetic Field  

NASA Technical Reports Server (NTRS)

This image shows the orientation and magnitude of the magnetic field measured by the MGS magnetometer as it sped over the surface of Mars during an early aerobraking pass (Day of the year, 264; 'P6' periapsis pass). At each point along the spacecraft trajectory we've drawn vectors in the direction of the magnetic field measured at that instant; the length of the line is scaled to show the relative magnitude of the field. Imagine traveling along with the MGS spacecraft, holding a string with a magnetized needle on one end: this essentially a compass with a needle that is free to spin in all directions. As you pass over the surface the needle would swing rapidly, first pointing towards the planet and then rotating quickly towards 'up' and back down again. All in a relatively short span of time, say a minute or two, during which time the spacecraft has traveled a couple of hundred miles. You've just passed over one of many 'magnetic anomalies' thus far detected near the surface of Mars. A second major anomaly appears a little later along the spacecraft track, about 1/4 the magnitude of the first - can you find it? The short scale length of the magnetic field signature locates the source near the surface of Mars, perhaps in the crust, a 10 to 75 kilometer thick outer shell of the planet (radius 3397 km).

The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. JPL is an operating division of California Institute of Technology (Caltech).

1997-01-01

384

Aggregation of magnetic holes in a rotating magnetic field  

E-print Network

We have experimentally investigated field induced aggregation of nonmagnetic particles confined in a magnetic fluid layer when rotating magnetic fields were applied. After application of a magnetic field rotating in the plane of the fluid layer, the single particles start to form two-dimensional (2D) clusters, like doublets, triangels, and more complex structures. These clusters aggregated again and again to form bigger clusters. During this nonequilibrium process, a broad range of cluster sizes was formed, and the scaling exponents, $z$ and $z'$, of the number of clusters $N(t)\\sim t^{z'}$and average cluster size $S(t)\\sim t^{z}$ were calculated. The process could be characterized as diffusion limited cluster-cluster aggregation. We have found that all sizes of clusters that occured during an experiment, fall on a single curve as the dynamic scaling theory predicts. Hovewer, the characteristic scaling exponents $z',\\: z$ and crossover exponents $\\Delta$ were not universal. A particle tracking method was used to find the dependence of the diffusion coefficients $D_{s}$ on cluster size $s$. The cluster motions show features of \\textit{\\emph{Brownian}} motion. The average diffusion coefficients $$ depend on the cluster sizes $s$ as a power law $\\propto s^{\\gamma}$ where values of $\\gamma$ as different as $\\gamma=-0.62\\pm0.19$ and $\\gamma=-2.08\\pm0. were found in two of the experiments.

Jozef ?ernk; Geir Helgesen

2008-06-20

385

Magnetic field gradients and their uses in the study of the earth's magnetic field  

NASA Technical Reports Server (NTRS)

Magnetic field gradients are discussed from the standpoint of their usefulness in modeling crustal magnetizations. The fact that gradients enhance shorter wavelength features helps reduce both the core signal and the signal from external fields in comparison with the crustal signal. If the gradient device can be oriented, then directions of lineation can be determined from single profiles, and anomalies caused by unlineated sources can be identified.

Harrison, C. G. A.; Southam, J. R.

1991-01-01

386

The Magnetic Field of Planet Earth  

NASA Astrophysics Data System (ADS)

The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks have quietly recorded much of its history. The usefulness of magnetic field charts for navigation and the dedication of a few individuals have also led to the patient construction of some of the longest series of quantitative observations in the history of science. More recently even more systematic observations have been made possible from space, leading to the possibility of observing the Earths magnetic field in much more details than was previously possible. The progressive increase in computer power was also crucial, leading to advanced ways of handling and analyzing this considerable corpus of data. This possibility, together with the recent development of numerical simulations, has led to the development of a very active field in Earth science. In this paper, we make an attempt to provide an overview of where the scientific community currently stands in terms of observing, interpreting and understanding the past and present behavior of the so-called main magnetic field produced within the Earths core. The various types of data are introduced and their specific properties explained. The way those data can be used to derive the time evolution of the core field, when this is possible, or statistical information, when no other option is available, is next described. Special care is taken to explain how information derived from each type of data can be patched together into a consistent description of how the core field has been behaving in the past. Interpretations of this behavior, from the shortest (1 yr) to the longest (virtually the age of the Earth) time scales are finally reviewed, underlining the respective roles of the magnetohydodynamics at work in the core, and of the slow dynamic evolution of the planet as a whole.

Hulot, G.; Finlay, C. C.; Constable, C. G.; Olsen, N.; Mandea, M.

2010-05-01

387

Statistics of the Earth's magnetic field with applications  

Microsoft Academic Search

This thesis discusses some statistical properties of the Earth's magnetic field and presents a statistical model of the field. In the final chapter, statistical models and inverse theory developed by George Backus are used to estimate low degree gauss coefficients of the magnetic field produced by sources in the core. Chapter 1 demonstrates that the Earth's non-dipole magnetic field need

Andrew David Walker

1997-01-01

388

Stellar Physics and Stellar Activity Magnetic fields in massive stars  

E-print Network

Stellar Physics and Stellar Activity Magnetic fields in massive stars S. Hubrig, I. Ilyin (AIP), M about the existence, origin, and role of magnetic fields in massive OB stars. During our recent stars in clusters and in the field five stars with mean longitudinal magnetic fields in the range from

389

Magnetic Fields in a Sample of Nearby Spiral Galaxies  

E-print Network

Both observations and modelling of magnetic fields in the diffuse interstellar gas of spiral galaxies are well developed but the theory has been confronted with observations for only a handful of individual galaxies. There is now sufficient data to consider statistical properties of galactic magnetic fields. We have collected data from the literature on the magnetic fields and interstellar media (ISM) of 20 spiral galaxies, and tested for various physically motivated correlations between magnetic field and ISM parameters. Clear correlations emerge between the total magnetic field strength and molecular gas density as well as the star formation rate. The magnetic pitch angle exhibits correlations with the total gas density, the star formation rate and the strength of the axisymmetric component of the mean magnetic field. The total and mean magnetic field strengths exhibit noticeable degree of correlation, suggesting a universal behaviour of the degree of order in galactic magnetic fields. We also compare the p...

Van Eck, Cameron; Shukurov, Anvar; Fletcher, Andrew

2014-01-01

390

A new Model of Saturn's Magnetic Field  

NASA Astrophysics Data System (ADS)

Using data from the Cassini spacecraft, we have created a new model of Saturn's magnetic field model that includes non-axisymmetric components. Previous solutions have not unambiguously resolved such components, instead being limited to (spin) axisymmetric components. We analyse the model using resolution analysis, error analysis and spectral analysis. We also examine Slepian basis functions in addition to the canonical spherical harmonics basis functions in an effort to negate the effects of the mostly equatorial coverage by the Cassini orbiter. Such poor coverage can lead to errors when using spherical harmonics as global support is required to achieve orthogonality over the whole sphere whereas Slepian functions, which are orthogonal over both the whole sphere and the region of data coverage, and which have their energy optimally concentrated in the spatial and spectral domain, may be able to obtain much better results. Our model was derived using a regularized weighted linear least-squares estimation of model coefficients in which we estimated internal and external coefficients simultaneously as opposed to assuming and subtracting out an external field of specific shape and size. While small, we investigate whether the non-axisymmetric signature is sufficient to use in an autocorrelation timeseries analysis of the magnetic field measurements to infer a rotation rate directly from the internally generated magnetic field.

Sterenborg, M. G.; Bloxham, J.

2008-12-01

391

Magnetic Fields in Population III Star Formation  

SciTech Connect

We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg

2012-02-22

392

MAGNETIC FIELDS IN POPULATION III STAR FORMATION  

SciTech Connect

We study the buildup of magnetic fields during the formation of Population III star-forming regions by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32, and 64 zones per Jeans length, and study the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully resolved calculations. We have also identified a relatively surprising phenomenon that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

Turk, Matthew J.; Bryan, Greg L. [Department of Astronomy, Columbia University, 538 West 120th Street, New York, NY 10027 (United States); Oishi, Jeffrey S.; Abel, Tom, E-mail: matthewturk@gmail.com [Kavli Institute for Particle Physics and Cosmology, Stanford University, Stanford, CA 94305 (United States)

2012-02-01

393

Magnetic Fields and Galactic Star Formation Rates  

E-print Network

The regulation of galactic-scale star formation rates (SFRs) is a basic problem for theories of galaxy formation and evolution: which processes are responsible for making observed star formation rates so inefficient compared to maximal rates of gas content divided by dynamical timescale? Here we study the effect of magnetic fields of different strengths on the evolution of molecular clouds within a kiloparsec patch of a disk galaxy. Including an empirically motivated prescription for star formation from dense gas ($n_{\\rm{H}}>10^5\\:{\\rm{cm}^{-3}}$) at an efficiency of 2\\% per local free fall time, we derive the amount of suppression of star formation by magnetic fields compared to the nonmagnetized case. We find GMC fragmentation, dense clump formation and SFR can be significantly affected by the inclusion of magnetic fields, especially in our strongest investigated $B$-field case of $80\\:{\\rm{\\mu}}$G. However, our chosen kpc scale region, extracted from a global galaxy simulation, happens to contain a starbu...

Van Loo, Sven; Falle, Sam A E G

2014-01-01

394

Ram pressure stripping in elliptical galaxies - II. Magnetic field effects  

NASA Astrophysics Data System (ADS)

We investigate the effects of magnetic fields and turbulence on ram pressure stripping in elliptical galaxies using ideal magnetohydrodynamic simulations. We consider weakly magnetized interstellar medium (ISM) characterized by subsonic turbulence, and two orientations of the magnetic fields in the intracluster medium (ICM) - parallel and perpendicular to the direction of the galaxy motion through the ICM. While the stronger turbulence enhances the ram pressure stripping mass-loss, the magnetic fields tend to suppress the stripping rates, and the suppression is stronger for parallel fields. However, the effect of magnetic fields on the mass stripping rate is mild. Nevertheless, the morphology of the stripping tails depends significantly on the direction of the ICM magnetic field. The effect of the magnetic field geometry on the tail morphology is much stronger than that of the level of the ISM turbulence. The tail has a highly collimated shape for parallel fields, while it has a sheet-like morphology in the plane of the ICM magnetic field for perpendicular fields. The magnetic field in the tail is amplified irrespectively of the orientation of the ICM field. More strongly magnetized regions in the ram pressure stripping tails are expected to have systematically higher metallicity due to the strong concentration of the stripped ISM than the less magnetized regions. Strong dependence of the morphology of the stripped ISM on the magnetic field could potentially be used to constrain the relative orientation of the ram pressure direction and the dominant component of the ICM magnetic field.

Shin, Min-Su; Ruszkowski, Mateusz

2014-12-01

395

Magnetic-field enhancement in gold nanosandwiches  

NASA Astrophysics Data System (ADS)

Using dispersive finite-difference time-domain (D-FDTD) simulations, we show that a pair of gold nanodisks stacked in a 'sandwich'-like (end-fire) configuration produces a large enhancement of the magnetic field when irradiated with a plane optical wave, if the distance between the nanodisks is optically small. The effect, which can be rationalized in terms of a magnetic dipole resonance, is due the excitation of a hybridized asymmetric plasmon mode, in which the induced electrical dipoles in the two disks oscillate out-of-phase. The strong magnetic response, together with the simple morphology, suggests that Au nanosandwiches are suitable elementary building blocks for optical metamaterials that exhibit negative refraction.

Pakizeh, T.; Abrishamian, M. S.; Granpayeh, N.; Dmitriev, A.; Kll, M.

2006-09-01

396

A compact high field magnetic force microscope.  

PubMed

We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114

Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou

2014-12-01

397

Stable magnetic field configurations in stars  

NASA Astrophysics Data System (ADS)

Long-lived, large-scale magnetic field configurations with similar total fluxes exist in at least three very different, although related kind of stars: upper main sequence stars, white dwarfs, and neutron stars (e.g. Reisenegger 2001). Much or all of the volume of these stars is stably stratified, so there is no convection that could maintain these fields through dynamo processes (except in the cores of upper main sequence stars). Magnetohydrodynamic simulations of stably stratified stars (Braithwaite & Spruit 2004, 2006; Braithwaite & Nordlund 2006) suggest that configurations with linked poloidal and toroidal fields get spontaneously established and might be stable over long times. Physical arguments show that such configurations are in fact natural and that the stable stratification is likely to play a crucial role in their stability. Thus, contrary to assumptions in recent papers, the field is not force-free, and the fluid cannot be taken to be barotropic. Work is in progress to represent these fields analytically and investigate the conditions for their stability. In the case of neutron stars with strong enough fields, the stable stratification can be overcome by long-term, dissipative processes such as beta decays and ambipolar diffusion (Goldreich & Reisenegger 1992; Reisenegger et al. 2005), leading to the release of magnetic energy and potentially explaining the energy source for the "magnetar" phenomenon (Thompson & Duncan 1993, 1996).

Reisenegger, Andreas; Munoz, Francisco; Santos, Raul

398

NMR in rotating magnetic fields: Magic angle field spinning  

SciTech Connect

Magic angle sample spinning has been one of the cornerstones in high-resolution solid state NMR. Spinning frequencies nowadays have increased by at least one order of magnitude over the ones used in the first experiments and the technique has gained tremendous popularity. It is currently a routine procedure in solid-state NMR, high-resolution liquid-state NMR and solid-state MRI. The technique enhances the spectral resolution by averaging away rank 2 anisotropic spin interactions thereby producing isotropic-like spectra with resolved chemical shifts and scalar couplings. Andrew proposed that it should be possible to induce similar effects in a static sample if the direction of the magnetic field is varied, e.g., magic-angle rotation of the B0 field (B0-MAS) and this has been recently demonstrated using electromagnetic field rotation. Here we discuss on the possibilities to perform field rotation using alternative hardware, together with spectroscopic methods to recover isotropic resolution even in cases where the field is not rotating at the magic angle. Extension to higher magnetic fields would be beneficial in situations where the physical manipulation of the sample is inconvenient or impossible. Such situations occur often in materials or biomedical samples where ''ex-situ'' NMR spectroscopy and imaging analysis is needed.

Sakellariou, D.; Meriles, C.; Martin, R.; Pines, A.

2004-09-10

399

Electric and magnetic fields at power frequencies.  

PubMed

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

Miller, Anthony B; Green, Lois M

2010-01-01

400

Interplanetary Magnetic Field Guiding Relativistic Particles  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

401

Measurements of magnetic field stability in inhomogeneous magnetic fields at low temperature  

NASA Astrophysics Data System (ADS)

We present an original method for field stability measurements in a bath of liquid helium. This method is used to validate the power supply of a superconductive magnet operating in driven mode. The experiment consists in the measurement of the NMR signal of a sample of liquid 3He, placed inside the field of a test magnet driven by a power supply. The homogeneity of the magnet is a strongly limiting factor for measurements but through the use of an inductively coupled microcoil and careful signal processing, a precision of 5.5 ppm was achieved.

Hugon, Cedric; Jacquinot, Jacques-Francois; Sakellariou, Dimitris

2010-01-01

402

Geometric Intersection Problems  

Microsoft Academic Search

We develop optimal algorithms for forming the intersection of geometric objects in the plane and apply them to such diverse problems as linear programming, hidden-line elimination, and wire layout. Given N line segments in the plane, finding all intersecting pairs requires O(N2) time. We give an O(N log N) algorithm to determine whether any two intersect and use it to

Michael Ian Shamos; Dan Hoey

1976-01-01

403

Control of stochasticity in magnetic field lines  

E-print Network

We present a method of control which is able to create barriers to magnetic field line diffusion by a small modification of the magnetic perturbation. This method of control is based on a localized control of chaos in Hamiltonian systems. The aim is to modify the perturbation locally by a small control term which creates invariant tori acting as barriers to diffusion for Hamiltonian systems with two degrees of freedom. The location of the invariant torus is enforced in the vicinity of the chosen target. Given the importance of confinement in magnetic fusion devices, the method is applied to two examples with a loss of magnetic confinement. In the case of locked tearing modes, an invariant torus can be restored that aims at showing the current quench and therefore the generation of runaway electrons. In the second case, the method is applied to the control of stochastic boundaries allowing one to define a transport barrier within the stochastic boundary and therefore to monitor the volume of closed field lines.

Cristel Chandre; Michel Vittot; Guido Ciraolo; Philippe Ghendrih; Ricardo Lima

2005-04-14

404

Magnetic Resonance Imaging at Ultrahigh Fields  

PubMed Central

Since the introduction of 4 T human systems in three academic laboratories circa 1990, rapid progress in imaging and spectroscopy studies in humans at 4 T and animal model systems at 9.4 T have led to the introduction of 7 T and higher magnetic fields for human investigation at about the turn of the century. Work conducted on these platforms has demonstrated the existence of significant advantages in SNR and biological information content at these ultrahigh fields, as well as the presence of numerous challenges. Primary difference from lower fields is the deviation from the near field regime; at the frequencies corresponding to hydrogen resonance conditions at ultrahigh fields, the RF is characterized by attenuated traveling waves in the human body, which leads to image nonuniformities for a given sample-coil configuration because of interferences. These nonuniformities were considered detrimental to the progress of imaging at high field strengths. However, they are advantageous for parallel imaging for signal reception and parallel transmission, two critical technologies that account, to a large extend, for the success of ultrahigh fields. With these technologies, and improvements in instrumentation and imaging methods, ultra-high fields have provided unprecedented gains in imaging of brain function and anatomy, and started to make inroads into investigation of the human torso and extremities. As extensive as they are, these gains still constitute a prelude to what is to come given the increasingly larger effort committed to ultrahigh field research and development of ever better instrumentation and techniques. PMID:24686229

Ugurbil, Kamil

2014-01-01

405

Magnetic Field Fluctuations in Saturn's Magnetosphere  

NASA Astrophysics Data System (ADS)

In the framework of turbulence, we analyze the statistical properties of magnetic field fluctuations measured by the Cassini spacecraft inside Saturn's plasma sheet. In the spacecraft-frame power spectra of the fluctuations we identify two power-law spectral ranges seperated by a spectral break around ion gyro-frequencies of O+ and H+. The spectral indices of the low frequency power-law are found to be between 5-3 (for fully developed cascades) and 1 (during energy input on the corresponding scales). Above the spectral break there is a constant power-law with mean spectral index ~2.5 indicating a permament turbulent cascade in the kinetic range. An increasing non-gaussian probability density with frequency indicates the build-up of intermittency. Correlations of plasma parameters with the spectral indices are examined and it is found that the power-law slope depends on background magnetic field strength and plasma beta.

von Papen, Michael; Saur, Joachim; Alexandrova, Olga

2013-04-01

406

Neutrino reactions in strong magnetic field  

NASA Technical Reports Server (NTRS)

Presentation of the energy losses due to several neutrinos processes: (1) synchrotron neutrinos, (2) pair annihilation neutrinos, (3) plasmon neutrinos, and (4) photoneutrinos in the presence of a superstrong magnetic field. Numerical results are tabulated and illustrated for several values of densities and temperatures. In the low density regime, the presence of a magnetic field decreases the luminosity, whereas the opposite is true at higher densities. This last effect is, however, almost entirely due to the existence of a new process, the synchrotron neutrinos that disappear when H goes to zero. Even though the overall effect can only be quantitatively ascertained after a complete cooling computation is performed, one should however expect a much lower temperature for neutron star surface than the one computed in the case where H is zero.

Canuto, V.; Chiuderi, C.; Chou, C. K.; Fassio-Canuto, L.

1974-01-01

407

The vector structure of active magnetic fields  

NASA Technical Reports Server (NTRS)

Observations are needed to show the form of the strains introduced into the fields above the surface of the Sun. The longitudinal component alone does not provide the basic information, so that it has been necessary in the past to use the filamentary structure observed in H sub alpha to supplement the longitudinal information. Vector measurements provide the additional essential information to determine the strains, with the filamentary structure available as a check for consistency. It is to be expected, then, that vector measurements will permit a direct mapping of the strains imposed on the magnetic fields of active regions. It will be interesting to study the relation of those strains to the emergence of magnetic flux, flares, eruptive prominences, etc. In particular we may hope to study the relaxation of the strains via the dynamical nonequilibrium.

Parker, E. N.

1985-01-01

408

The measurement and analysis of the magnetic field of a synchrotron light source magnet  

E-print Network

In this thesis a unique system is used to measure the magnetic field of a superconducting synchrotron light source magnet. The magnet measured is a superferric dipole C-magnet designed to produce a magnetic field up to 3 Tesla in magnitude. Its...

Graf, Udo Werner

2012-06-07

409

Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field  

E-print Network

Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field ZHEN Liang( )1 27599-3255, USA Received 29 June 2006; accepted 15 January 2007 Abstract: Structural and magnetic properties of Fe-25Cr-12Co-1Si alloy thermo-magnetically treated under different external magnetic field

Qin, Lu-Chang

410

Effects of MHD slow shocks propagating along magnetic flux tubes in a dipole magnetic field  

Microsoft Academic Search

Variations of the plasma pressure in a magnetic flux tube can produce MHD waves evolving into shocks. In the case of a low plasma beta, plasma pressure pulses in the magnetic flux tube generate MHD slow shocks propagating along the tube. For converging magnetic field lines, such as in a dipole magnetic field, the cross section of the magnetic flux

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

2002-01-01

411

Periodicities in the interplanetary magnetic field polarity  

Microsoft Academic Search

The daily data of the polarity of the interplanetary magnetic field for the years 1926-1982 were studied by means of a power spectrum analysis in order to determine prevailing structures of this polarity as well as to search for recurrences in those structures. On a global scale, the presence of significant peaks at about 27.5, 13.5, 9.1 and 6.8 days

A. L. C. Gonzalez; W. D. Gonzalez

1987-01-01

412

OGO-A MAGNETIC FIELD OBSERVATIONS  

Microsoft Academic Search

This paper summarizes the new findings that have come from the intial study of the OGO-A fluxgate magnetometer measurements between 4 and 24.5 Rs (earth radii). These include the following' (a) A model magnetic field profile of the cross-sectional structure of the bow shock is derived in terms of the sharpness of the interface, the rise time, and the total

J. P. Heppner; M. Sugiura; T. L. Skillman; B. G. Ledley; M. Campbell

1967-01-01

413

The Galactic halo magnetic field revisited  

NASA Astrophysics Data System (ADS)

Recently, Sun et al. published new Galactic 3D-models of magnetic fields in the disk and halo of the Milky Way and the distribution of cosmic-ray electron density by taking into account the thermal electron density model NE2001 by Cordes & Lazio. The models successfully reproduce observed continuum and polarization all-sky maps and the distribution of rotation measures of extragalactic sources across the sky. However, the model parameters obtained for the Galactic halo, although reproducing the observations, seem physically unreasonable: the magnetic field needs to be significantly stronger in the Galactic halo than in the plane and the cosmic-ray distribution must be truncated at about 1 kpc to avoid excessive synchrotron emission from the halo. The reason for these unrealistic parameters was the low scale-height of the warm thermal gas of about 1 kpc adopted in the NE2001 model. However, this scale-height seemed reasonable and was well studied by numerous investigations. Recently, the scale-height of the warm gas in the Galaxy was revised by Gaensler et al. to about 1.8 kpc, by showing that the 1 kpc scale-height results from a systematic bias in the analysis of pulsar data. This implies a higher thermal electron density in the Galactic halo, which in turn reduces the halo magnetic field strength to account for the observed rotation measures of extragalactic sources. We slightly modified the NE2001 model according to the new scale-height and revised the Sun et al. model parameters accordingly: the strength of the regular halo magnetic field is now 2 ?G or lower, and the physically unrealistic cutoff in z for the cosmic-ray electron density is removed. The simulations based on the revised 3D-models reproduce all-sky observations as before.

Sun, Xiao-Hui; Reich, Wolfgang

2010-12-01

414

Slowly rotating pulsars and magnetic field decay  

Microsoft Academic Search

Two dozen long period pulsars are separated from the swarm of ordinary pulsars by an obvious gap in the P versus Sd diagram (where Sd=log˙(P)+21.0), with a plausible upper boundary for ordinary pulsars. Possible pulsar evolutionary tracks are discussed to explain the diagram in terms of previously suggested scenarios of magnetic field decay. The (P-Sd) diagram is difficult to understand

J. L. Han

1997-01-01

415

Heavy quarks in a magnetic field  

E-print Network

The motion of a heavy charged quark in a magnetic field is analyzed in the vacuum of strongly coupled CFT. The motion of the quark is dissipative. It moves in spiral until it eventually comes to rest. The world-sheet geometry is locally AdS_2 but has a time dependent horizon. The string profile in the static gauge extends from the boundary till a point where an embedding singularity exists. Connections with other circular string motions are established.

Elias Kiritsis; George Pavlopoulos

2011-11-01

416

Evolution of Rotating Molecular Cloud Core with Oblique Magnetic Field  

E-print Network

We studied the collapse of rotating molecular cloud cores with inclined magnetic fields, based on three-dimensional numerical simulations.The numerical simulations start from a rotating Bonnor-Ebert isothermal cloud in a uniform magnetic field. The magnetic field is initially taken to be inclined from the rotation axis. As the cloud collapses, the magnetic field and rotation axis change their directions. When the rotation is slow and the magnetic field is relatively strong, the direction of the rotation axis changes to align with the magnetic field, as shown earlier by Matsumoto & Tomisaka. When the magnetic field is weak and the rotation is relatively fast, the magnetic field inclines to become perpendicular to the rotation axis. In other words, the evolution of the magnetic field and rotation axis depends on the relative strength of the rotation and magnetic field. Magnetic braking acts to align the rotation axis and magnetic field, while the rotation causes the magnetic field to incline through dynamo action. The latter effect dominates the former when the ratio of the angular velocity to the magnetic field is larger than a critical value \\Omega_0/ B_0 > 0.39 G^1/2 c_s^-1, where B_0, \\Omega_0, G, and c_s^-1 denote the initial magnetic field, initial angular velocity, gravitational constant, and sound speed, respectively. When the rotation is relatively strong, the collapsing cloud forms a disk perpendicular to the rotation axis and the magnetic field becomes nearly parallel to the disk surface in the high density region. A spiral structure appears due to the rotation and the wound-up magnetic field in the disk.

Masahiro N. Machida; Tomoaki Matsumoto; Tomoyuki Hanawa; Kohji Tomisaka

2006-02-02

417

Cosmological magnetic fields from inflation and backreaction  

SciTech Connect

We study the backreaction problem in a mechanism of magnetogenesis from inflation. In usual analysis, it has been assumed that the backreaction due to electromagnetic fields spoils inflation once it becomes important. However, there exists no justification for this assumption. Hence, we analyze magnetogenesis from inflation by taking into account the backreaction. On the contrary to the naive expectation, we show that inflation still continues even after the backreaction begins to work. Nevertheless, it turns out that creation of primordial magnetic fields is significantly suppressed due to the backreaction.

Kanno, Sugumi [Centre for Particle Theory, Department of Mathematical Sciences, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Soda, Jiro; Watanabe, Masa-aki, E-mail: sugumi.kanno@durham.ac.uk, E-mail: jiro@tap.scphys.kyoto-u.ac.jp, E-mail: mwatanabe@tap.scphys.kyoto-u.ac.jp [Department of Physics, Kyoto University, Kyoto, 606-8501 (Japan)

2009-12-01

418

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field  

E-print Network

We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

Rabhi, A; Providncia, C; Vidaa, I

2014-01-01

419

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field  

E-print Network

We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

A. Rabhi; M. A. Prez-Garca; C. Providncia; I. Vidaa

2014-10-10

420

Magnetic Field Activities for the High School Classroom  

NSDL National Science Digital Library

This unit is designed to acquaint students with the properties of magnetic fields. It is meant to introduce the idea of a "field" through investigations of magnetic fields as produced by various common magnetic materials and direct electrical currents. They will learn that the difference between a magnetic field and a gravitational field is that a gravitational field, in the experience of a student, always points downward and is always of the same strength. Magnetic fields are not limited to one direction or strength. Further, all students will know, by the mid-point of this unit, that magnetic fields are inherently loop shaped. Familiarity with the uniform gravitational field of classical Newtonian dynamics and kinematics is not required. As they complete the unit, students will gain an appreciation for the vector nature of fields, the ubiquity of field sources in the environment, and the ability to visualize such fields as three-dimensional entities.

Eckel, Ed; Friel, Matthew

421

Titan's Magnetic Field Signature During the First Cassini Encounter  

Microsoft Academic Search

The magnetic field signature obtained by Cassini during its first close encounter with Titan on 26 October 2004 is presented and explained in terms of an advanced model. Titan was inside the saturnian magnetosphere. A magnetic field minimum before closest approach marked Cassini's entry into the magnetic ionopause layer. Cassini then left the northern and entered the southern magnetic tail

Heiko Backes; Fritz M. Neubauer; Michele K. Dougherty; Nicholas Achilleos; Nicolas Andr; Christopher S. Arridge; Cesar Bertucci; Geraint H. Jones; Krishan K. Khurana; Christopher T. Russell; Alexandre Wennmacher

2005-01-01

422

The Earth' magnetic field in the last 100 kyr  

Microsoft Academic Search

Rock-magnetic and palaeo-magnetic data from sediments of two Italian lakes provide a reconstruction of the Earth' magnetic field in the last 100 kyr. Since the measurements contain also the climate signal, we apply the Independent Component Analysis in order to extract the signal of the Earth' magnetic field.

N. Marwan; U. Schwarz; J. Kurths

2003-01-01

423

Solidifying Mn/Bi in a Magnetic Field  

NASA Technical Reports Server (NTRS)

Report describes experiments in directional solidification of eutectic Mn/Bi in magnetic field. Study determines whether effects of gravitationally-induced convection reduced or eliminated by magnetic field. Morphological, thermal, and magnetic analyses done on samples grown at various speeds and various applied strengths. Magnetic effects similar to those of low gravity.

Decarlo, J. L.; Pirich, Ron G.

1987-01-01

424

Magnetic-field-induced crystallographic texture enhancement in cold-deformed FePt nanostructured magnets  

E-print Network

Magnetic-field-induced crystallographic texture enhancement in cold-deformed FePt nanostructured magnets B. Z. Cuia and K. Han National High Magnetic Field Laboratory, Florida State University Grenoble, France H. J. Schneider-Muntau National High Magnetic Field Laboratory, Florida State University

Garmestani, Hamid

425

Critical magnetic fields for the magnetic Dirac-Coulomb operator Maria J. ESTEBAN  

E-print Network

Critical magnetic fields for the magnetic Dirac-Coulomb operator Maria J. ESTEBAN C://www.ceremade.dauphine.fr/ e esteban/ John60, Edinburgh, June 2008 ­ p.1/20 #12;Physical problem Very strong magnetic fields/20 #12;Physical problem Very strong magnetic fields could : ­ destabilize matter, distorting atoms

Eilbeck, Chris

426

Yoke-free magnetic system for low field studies in magnetically affected reaction yield spectroscopy  

Microsoft Academic Search

The article reports the development of a specialized magnetic system for application in low field studies of chemical reactions involving paramagnetic intermediates. We have designed and built a yoke-free magnetic system optimized for creating rather low static homogeneous magnetic fields that can be cleanly swept through zero value. The actually built system creates magnetic field in the range from ``-500''

Evgeny V. Kalneus; Dmitri V. Stass; Yuri A. Grishin

2005-01-01

427

Nanoscale Magnetic Behavior of C60 Thin Films in Earth Magnetic Field under Polarization Light Influences  

Microsoft Academic Search

Magnetic behavior of C60 thin films in the Earth's magnetic field under polarization light influence is presented. Transformation of magnetic field for two fullerene thin films of different thickness is investigated. Two proton magnetometers were used for these measurements. Samples of 30nm and 250nm thickness illustrate a significant change of magnetic field intensity under the influence of polarization light, in

A. Nikolic; Lj. Petrov; Dj. Koruga; S. Mihajlovic

2005-01-01

428

Physics in Strong Magnetic Fields Near Neutron Stars.  

ERIC Educational Resources Information Center

Discussed are the behaviors of particles and energies in the magnetic fields of neutron stars. Different types of possible research using neutron stars as a laboratory for the study of strong magnetic fields are proposed. (CW)

Harding, Alice K.

1991-01-01

429

A model of interplanetary and coronal magnetic fields  

Microsoft Academic Search

A model of the large-scale magnetic field structure above the photosphere uses a Green's function solution to Maxwell's equations. Sources for the magnetic field are related to the observed photospheric field and to the field computed at a source surface about 0.6 R? above the photosphere. The large-scale interplanetary magnetic field sector pattern is related to the field pattern at

Kenneth H. Schatten; John M. Wilcox; Norman F. Ness

1969-01-01

430

The scientific case for magnetic field satellites  

NASA Technical Reports Server (NTRS)

To make full use of modern magnetic data and the paleomagnetic record, we must greatly improve our understanding of how the geodynamo system works. It is clearly nonlinear, probably chaotic, and its dimensionless parameters cannot yet be reproduced on a laboratory scale. It is accessible only to theory and to measurements made at and above the earth's surface. These measurements include essentially all geophysical types. Gravity and seismology give evidence for undulations in the core-mantle boundary (CMB) and for temperature variations in the lower mantle which can affect core convection and hence the dynamo. VLBI measurements of the variations in the Chandler wobble and length of day are affected by, among other things, the electromagnetic and mechanical transfer of angular momentum across the CMB. Finally, measurements of the vector magnetic field, its intensity, or its direction, give the most direct access to the core dynamo and the electrical conductivity of the lower mantle. The 120 gauss coefficients of degrees up to 10 probably come from the core, with only modest interference by mantle conductivity and crustal magnetization. By contrast, only three angular accelerations enter the problem of angular momentum transfer across the CMB. Satellite measurements of the vector magnetic field are uniquely able to provide the spatial coverage required for extrapolation to the CMB, and to isolate and measure certain magnetic signals which to the student of the geodynamo represent noise, but which are of great interest elsewhere in geophysics. Here, these claims are justified and the mission parameters likely to be scientifically most useful for observing the geodynamo system are described.

Backus, George E. (editor); Benton, Edward R.; Harrison, Christopher G. A.; Heirtzler, James R.

1987-01-01

431

Improved Magnetic Field Generation Efficiency and Higher Temperature Spheromak Plasmas  

SciTech Connect

New understanding of the mechanisms governing the observed magnetic field generation limits on the sustained spheromak physics experiment has been obtained. Extending the duration of magnetic helicity injection during the formation of a spheromak and optimizing the ratio of injected current to bias flux produce higher magnetic field plasmas with record spheromak electron temperatures. To explore magnetic field buildup efficiency limits, the confinement region geometry was varied resulting in improved field buildup efficiencies.

Wood, R D; Hill, D N; McLean, H S; Hooper, E B; Hudson, B F; Moller, J M; Romero-Talamas, C A

2008-09-15

432

Turbulent magnetic field fluctuations in Saturn's magnetosphere  

NASA Astrophysics Data System (ADS)

We analyze the statistical properties of magnetic field fluctuations measured by the Cassini spacecraft inside Saturn's magnetosphere. We introduce Saturn's magnetosphere as a new laboratory for plasma turbulence, where background magnetic field is strong (1 nT = 0.07), and the ion plasma ?i is smaller than one. We also show that the dissipation of these magnetic field fluctuations has important implications for the magnetosphere. In a case study of the second orbit of Cassini around Saturn we show that at MHD scales, the spectra and the nature of fluctuations are characterized by large-scale nonstationary processes. The spectral slope varies between -0.8 and -1.7. At higher frequencies we observe a steeper spectrum with nearly constant power law exponent. A spectral break correlating with ion scales separates the two frequency ranges. We carry out a statistical study of high-frequency range fluctuations using the first seven orbits of Cassini. We find that the energy density of raw frequency spectra depends on radial distance from Saturn and thermal and magnetic pressures. However, normalized spectra depend only on ion plasma ?i. Closer to Saturn the spectral slope is about -2.3 and for radial distances r>9 Rs the average slope is -2.6. The fluctuations have probability density functions with increasingly non-Gaussian tails and a power law increase of flatness with frequency, which indicates intermittency. We estimate the total energy flux contained in the turbulent cascade as 60-100 GW, which is on the same order of magnitude as needed to heat an adiabatically expanding plasma to the temperatures measured in Saturn's magnetosphere.

von Papen, M.; Saur, J.; Alexandrova, O.

2014-04-01

433

Spectral signature of uncombed penumbral magnetic fields  

NASA Astrophysics Data System (ADS)

The uncombed penumbral model proposed by Solanki & Montavon (\\cite{sol93a}) is used to understand some recent observational results found in penumbrae. This model uses a penumbral magnetic field structured into horizontal flux tubes embedded in a more vertical background field. A modified version of this model, with a weaker field strength in the horizontal tubes, is used to explain the gradient with height of field strength and inclination found in studies using inversion techniques. These studies have found that over a range of 300 km, the field strength of the outer penumbra increases with height by more than 500 G. Similarly, the field inclination decreases with height by 30o in the same range of heights. We show that spectra generated by the uncombed model can give rise to these two effects as long as the horizontal tubes (of ~ 100 km diameter) remain unresolved. We also study the linear, quadratic and rms fluctuations of the inclination gradients that can be generated by the uncombed model. These gradients are found to be compatible with those obtained from the null divergence condition and those derived from observations of net circular polarization. A key ingredient to explain these gradients is the contribution of the two boundary layers that enclose the horizontal magnetic tubes as seen by the line-of-sight. Our realization of the uncombed model also predicts values of the net circular polarization observed with the Advanced Stokes Polarimeter. The existence of a pure background penumbral field as proposed by the model is, however, put into question.

Martnez Pillet, V.

2000-09-01

434

THE OUTER MAGNETIC FIELD OF L183  

SciTech Connect

The L183 (= L134N) dark molecular cloud has been probed using deep near-infrared imaging polarimetry of stars to beyond 14 mag in H band (1.6 {mu}m), using the Mimir instrument on the 1.83 m Perkins Telescope. Nearly 400 arcmin{sup 2} were surveyed, including the dense core in L183, as seen in WISE Band 3 (12 {mu}m) extinction, and the near surroundings, revealing 35 stars with either detected polarizations or significant upper limits. Stars with detected polarizations are reddened if closer than 8 arcmin (0.25 pc at the 110 pc cloud distance) and unreddened beyond. The polarimetric sample probes as close to the core as 3 arcmin (0.1 pc), where A{sub V} {approx} 14 mag. Compared to the relatively unextincted surrounding stars, the reddened stars show no increase in polarization with extinction, suggesting that all of the polarization is induced in the outer layers of the cloud. This 0.25 pc radius envelope magnetic field does show a strong interaction with the L183 dark cloud. The envelope field is also virtually perpendicular, on the plane of the sky, to the field seen at 850 {mu}m, though more closely aligned with the rotation axis of the dense gas core. The physical size scale at which the envelope and the core magnetic fields either decouple from each other or strongly modify their directions must be inside the 0.1 pc region probed here.

Clemens, Dan P., E-mail: clemens@bu.edu [Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States)

2012-03-20

435

Semiconductor Circuit Diagnostics By Magnetic Field Imaging  

NASA Astrophysics Data System (ADS)

At the forefront of IC technology development are 3D circuit technologies such as system-in-package (SiP), wafer-level-packaging (WLP), through-silicon-vias (TSV), stacked die approaches, flex packages, etc. They integrate multiple devices, many times stacking them in layers with complex, intricate and very long interconnections in significantly reduced area, in addition to an ever-increasing number of opaque layers. We could very well say that the near future looks like the perfect nightmare for the Failure Analysis (FA) engineer with localization of defects becoming a major challenge. Magnetic field imaging (MFI) allows the fields generated by the circuit currents to go through various packaging layers and be imaged. I will describe in this talk Magma, a scanning magnetic field imaging system based on a high temperature superconducting SQUID device based on YBa2Cu3O7-?. The HTS SQUIDs used have a noise level of 20pT/(Hz) and for typical scanning conditions, a field sensitivity of about 0.7 nT. While current shorts are imaged with spatial resolution, up to 3 micron (with peak localization) resistive opens can also be imaged and currently different strategies are being adapted for imaging opens with large working distances of 50-100s of microns. Higher spatial resolution (250nm) is obtained by the use of magneto-resistive devices as sensors though the working distance requirement is sever

Venkatesan, T.

2011-03-01

436

Evaluation of lightning induced magnetic fields inside reinforced concrete buildings  

E-print Network

Evaluation of lightning induced magnetic fields inside reinforced concrete buildings C. Miry, E of a reinforced concrete building against lightning induced effects is analyzed. Measurements of magnetic fields. Keywords-component: lightning currents, magnetic field, reinforced concrete buildings, numerical analysis I

437

Dispersive nonlinearities of QED vacuum in a periodic magnetic field  

Microsoft Academic Search

We investigate specific features of the dispersive vacuum polarization effects for the light propagation in magnetized vacuum which are induced due to spatial modulation of the magnetic field. The reciprocal lattice vectors associated with the periodic field are involved in the energy-momentum conservation for the photon interaction processes which allow elastic scattering of impinging photons by a strong magnetic field.

Gagik Yu. Kryuchkyan; Karen Z. Hatsagortsyan

2010-01-01

438

Magnetic fields and Faraday rotation in clusters of galaxies  

Microsoft Academic Search

We present a numerical approach to investigate the relationship between magnetic fields and Faraday rotation effects in clusters of galaxies. We can infer the structure and strength of intra-cluster magnetic fields by comparing our simulations with the observed polarization properties of extended cluster radio sources such as radio galaxies and halos. We find the observations require a magnetic field which

M. Murgia; F. Govoni; L. Feretti; G. Giovannini; D. Dallacasa; R. Fanti; G. B. Taylor; K. Dolag

2004-01-01

439

Probing primordial magnetic fields with the 21-cm fluctuations  

Microsoft Academic Search

Primordial magnetic fields possibly generated in the very early Universe are one of the candidates for the origin of magnetic fields observed in many galaxies and galaxy clusters. After recombination, the dissipation process of the primordial magnetic fields increases the baryon temperature. The Lorentz force acts on the residual ions and electrons to generate density fluctuations. These effects are imprinted

Hiroyuki Tashiro; Naoshi Sugiyama

2006-01-01

440

NASA Computational Case Study: Modeling Planetary Magnetic and Gravitational Fields  

NASA Technical Reports Server (NTRS)

In this case study, we model a planet's magnetic and gravitational fields using spherical harmonic functions. As an exercise, we analyze data on the Earth's magnetic field collected by NASA's MAGSAT spacecraft, and use it to derive a simple magnetic field model based on these spherical harmonic functions.

Simpson, David G.; Vinas, Adolfo F.

2014-01-01

441

Magnetic Field based Heading Estimation for Pedestrian Navigation Environments  

E-print Network

Magnetic Field based Heading Estimation for Pedestrian Navigation Environments Muhammad Haris Afzal held devices, these other sources are accelerometers for roll and pitch estimates and magnetic field sensors for the heading. In order to utilize the magnetic field sensors for heading estimation

Calgary, University of

442

Neutron scattering in magnetic fields (*) W. C. Koehler  

E-print Network

691 Neutron scattering in magnetic fields (*) W. C. Koehler Solid State Division, Oak Ridge. Abstract 2014 The use of magnetic fields in neutron scattering experimentation is reviewed briefly. Two) 691-695 SEPTEMBRE 1984, 1. Introduction. The uses of magnetic fields in neutron scattering experiments

Boyer, Edmond