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1

High-magnetic-field research collaborations  

SciTech Connect

This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to develop collaborations with the academic community to exploit scientific research potential of the pulsed magnetic fields that might be possible with electrically pulsed devices, as well as magneto-cumulative generators. The author started with a campaign of experiments using high-explosive-driven flux compression generators. The campaign's objective was to explore completely novel ideas in condensed-matter physics and chemistry. The initiative was very successful in pulling together top researchers from around the world.

Goettee, J.

1998-12-31

2

Sharpening the focus in EMF research. [Electric and Magnetic Fields  

SciTech Connect

Research results have yet to settle whether or not exposure to magnetic fields can adversely affect human health, but recent studies have provided strong pointers to several fertile areas of inquiry. EPRI is planning new studies that will dig deeper into the mysteries of these key focus areas, including questions about what wire code classifications really represent as indicators of residential magnetic field exposure and whether they are appropriate surrogates for actual exposure measurements. Other questions surround the hypothesis that magnetic fields could suppress production of the hormone melatonin, representing a possible mechanism of biological interaction. In addition to health studies, EPRI is continuing work in other parts of its comprehensive EMF research program, which includes identification of significant field sources and investigation of potential field management methods.

Moore, T. (Electric Power Research Inst., Palo Alto, CA (United States))

1992-03-01

3

Innovative research in electron microscopes, analysis of magnetic field distribution of some types of magnetic lenses by FEM  

Microsoft Academic Search

The paper deals with the partial results of the project specialized in innovation of research in magnetic lenses and chambers of electron microscopes. The paper is aimed at the simulation of magnetic field distribution of some types of magnetic lenses in software Ansys with the employment of results of magnetic measurements. Keywords-electron microscope, magnetic lens, magnetic field distribution

Regina Holcakova; Martin Marek

2011-01-01

4

The National High Magnetic Field Laboratory, A user facility in support of research in high magnetic fields  

SciTech Connect

The National High Magnetic Field Laboratory (NHMFL) develops and operates high magnetic field facilities at its main location at Florida State University, Tallahassee, as well as a pulsed magnetic field facility at Los Alamos National Laboratory. A number of specialized facilities are also available to collaborators at the University of Florida for research at ultra-low temperatures, advanced magnetic resonance imaging, and materials sciences. The NHMFL is supported by the United States National Science Foundation (NSF) and by the State of Florida. It is a user facility available to qualified users through a peer review proposal process. The facilities and staff support research and development at the extremes of parameter space. A part of its activities is devoted to the advancement of the state of the art of superconducting, pulsed, resistive, and hybrid magnets. This involves cryogenic materials research, the development of high strength, high conductivity conductors, and the development of low and ultra low temperature systems.

Crow, J.E.; Schneider-Muntau, H.J. [Florida State Univ., Tallahassee, FL (United States). National High Magnetic Field Laboratory; Parkin, D. [Los Alamos National Lab., NM (United States); Sullivan, N.S. [Florida Univ., Gainesville, FL (United States). Dept. of Physics

1993-09-01

5

Research Strategy for Electric and Magnetic Fields: Research Needs and Priorities.  

National Technical Information Service (NTIS)

The document is a research strategy for electric and magnetic fields (EMF). Research discussed will provide information to allow better assessment of any health effects that might be found to be associated with EMF. The discussion is devoted to EMF in the...

J. Elder

1991-01-01

6

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.

Universe, Windows T.

1997-12-03

7

PREFACE: Yamada Conference LX on Research in High Magnetic Fields (RHMF2006)  

NASA Astrophysics Data System (ADS)

The 60th Yamada Conference on Research in High Magnetic Fields (RHMF2006) was held at Sendai Civic Auditorium, Miyagi Prefecture, Japan, from 16 - 19 August 2006, as the 8th RHMF. The first was held in Osaka (1982) followed by Leuven (1988), Amsterdam (1991), Nijmegen (1994), Sydney (1997), Porto (2000), and Toulouse (2003). RHMF2006, which was also a satellite conference of the 17th International Conference on Magnetism (Kyoto, 20 - 25 August 2006), covered a broad range of topics concerned with research in high magnetic fields: (1) magnetism, (2) strongly correlated electron systems, (3) superconductors, (4) metals and metallic nanostructures, (5) molecular systems, (6) semiconductors, (7) field effects on non-magnetic systems, (8) neutron and x-ray experiments in high magnetic fields, (9) magnet technology, (10) measurement techniques in high magnetic fields, and (11) high field facilities. First of all we would like to express sincere thanks to the Yamada Science Foundation for their support and encouragement. We would like to thank all the members of the International Advisory Committee and the Program Committee for their collaboration. The conference was organized as usual with oral sessions having both invited and contributed talks and poster sessions. The technical program started on the morning of Thursday 17 August, with a tutorial lecture by Professor M von Ortenberg. The special posters were invited to introduce recent activities and up-to-date equipment of 17 high field facilities in the world. On the Friday evening, we had a banquet at Sendai City Museum for the history and culture of Sendai, with Emeritus Professor M Date (a Chairman for the first conference in Osaka) and many other guests. The conference was closed with a talk by Professor F Herlach on the afternoon of Saturday 19 August. We heard with great pleasure the announcement from Professor J Wosnitza that next RHMF will be held in Dresden in 2009. This conference had 197 participants, 9 of which were women and 62 were from 17 countries other than Japan. Finally we would like to thank all the participants and authors for their contributions to the success of RHMF2006. Mitsuhiro Motokawa Chairperson, RHMF2006 Conference photo

Motokawa, Mitsuhiro

2006-12-01

8

PREFACE: Yamada Conference LX on Research in High Magnetic Fields (RHMF2006)  

NASA Astrophysics Data System (ADS)

The 60th Yamada Conference on Research in High Magnetic Fields (RHMF2006) was held at Sendai Civic Auditorium, Miyagi Prefecture, Japan, from 16 19 August 2006, as the 8th RHMF. The first was held in Osaka (1982) followed by Leuven (1988), Amsterdam (1991), Nijmegen (1994), Sydney (1997), Porto (2000), and Toulouse (2003). RHMF2006, which was also a satellite conference of the 17th International Conference on Magnetism (Kyoto, 20 25 August 2006), covered a broad range of topics concerned with research in high magnetic fields: (1) magnetism, (2) strongly correlated electron systems, (3) superconductors, (4) metals and metallic nanostructures, (5) molecular systems, (6) semiconductors, (7) field effects on non-magnetic systems, (8) neutron and x-ray experiments in high magnetic fields, (9) magnet technology, (10) measurement techniques in high magnetic fields, and (11) high field facilities. First of all we would like to express sincere thanks to the Yamada Science Foundation for their support and encouragement. We would like to thank all the members of the International Advisory Committee and the Program Committee for their collaboration. The conference was organized as usual with oral sessions having both invited and contributed talks and poster sessions. The technical program started on the morning of Thursday 17 August, with a tutorial lecture by Professor M von Ortenberg. The special posters were invited to introduce recent activities and up-to-date equipment of 17 high field facilities in the world. On the Friday evening, we had a banquet at Sendai City Museum for the history and culture of Sendai, with Emeritus Professor M Date (a Chairman for the first conference in Osaka) and many other guests. The conference was closed with a talk by Professor F Herlach on the afternoon of Saturday 19 August. We heard with great pleasure the announcement from Professor J Wosnitza that next RHMF will be held in Dresden in 2009. This conference had 197 participants, 9 of which were women and 62 were from 17 countries other than Japan. Finally we would like to thank all the participants and authors for their contributions to the success of RHMF2006. Mitsuhiro Motokawa Chairperson, RHMF2006 Conference photo

Motokawa, Mitsuhiro

2006-12-01

9

Growth of pea epicotyl in low magnetic field implication for space research  

Microsoft Academic Search

A magnetic field is an inescapable environmental factor for plants on the earth. However, its impact on plant growth is not well understood. In order to survey how magnetic fields affect plant, Alaska pea seedlings were incubated under low magnetic field (LMF) and also in the normal geo-magnetic environment. Two-day-old etiolated seedlings were incubated in a magnetic shield box and

Y. Negishi; A. Hashimoto; M. Tsushima; C. Dobrota; M. Yamashita; T. Nakamura

1999-01-01

10

The Earth's Magnetic Field  

NSDL National Science Digital Library

The magnetic field of the Earth is contained in a region called the magnetosphere. The magnetosphere prevents most of the particles from the sun, carried in solar wind, from hitting the Earth. This site, produced by the University Corporation for Atmospheric Research (UCAR), uses text, scientific illustrations,and remote imagery to explain the occurrence and nature of planetary magnetic fields and magnetospheres, how these fields interact with the solar wind to produce phenomena like auroras, and how magnetic fields of the earth and other planets can be detected and measured by satellite-borne magnetometers.

11

Research to Investigate the Microstructure of the Internal Magnetic Field in Selected Magnetic Materials.  

National Technical Information Service (NTIS)

Section 1 describes the continuing investigation of intermetallic compounds having high magnetization and large magnetocrystalline anisotropy for possible application as permanent magnet materials. MOST OF THIS WORK HAS BEEN ON COMPOUNDS OF THE TYPE Co5R,...

J. J. Becker C. D. Graham J. S. Kasper J. S. Kouvel

1967-01-01

12

Research on electromagnetic relay’s dynamic characteristics disturbed by uniform static magnetic field  

Microsoft Academic Search

Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its\\u000a electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static\\u000a magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic\\u000a parameters (delay time, pick-up time,

Guo-fu Zhai; Qi-ya Wang; Wan-bin Ren

2008-01-01

13

Overview of epidemiologic research on electric and magnetic fields and cancer  

SciTech Connect

This overview of epidemiologic research addresses the potential role of 60 Hertz electric and magnetic fields (EMF) in the etiology of cancer. The key findings are summarized with notation of the methodological challenges with which investigators must content. Although exposure is ubiquitous, long-term average EMF is influenced primarily by the background levels in homes, use of selected electric appliances such as electric blankets, and workplace exposures to energized equipment. Studies of residential exposure have focused on childhood cancer, starting with the report of an excess of wire configurations associated with elevated magnetic fields near the homes of children who developed cancer compared to healthy children. Several subsequent studies have tended to confirm that association, although the evidence falls short of demonstrating a causal association between magnetic fields and cancer. Exposures from electric appliances have been less extensively pursued, with some suggestions of an association with childhood cancer. A more extensive literature has evaluated the association between workplace exposure to EMF, based on job titles of electrical workers and cancer. Across many different study designs and settings, certain groups of electrical workers show elevated occurrence of leukemia and brain cancer. The consistency of findings is notable, but the key question is whether the association with job title is due to EMF or some other agent in the workplace. Future research would benefit from specification of testable challenges to a causal association between EMF exposure in the home or workplace and cancer, along with continued efforts to improve our understanding and measurement of EMF exposure. 64 refs.

Savitz, D.A. (Univ. of North Carolina, Chapel Hill (United States))

1993-04-01

14

Research facilities of International Laboratory of High Magnetic Fields and Low Temperatures at Wroclaw  

NASA Astrophysics Data System (ADS)

International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw, Poland is financed by the Bulgarian Academy of Sciences, National Academy of Sciences of Ukraine, Polish Academy of Sciences and Russian Academy of Sciences as the main contributors. But the scientists from Germany, UK and other countries are also users of the Laboratory facilities. The Laboratory offers the measurements of the magnetic, transport and some optical properties, and magnetostriction both in permanent magnetic fields (Bitter and superconducting coils) up to 20 T, and in quasi-pulsed magnetic field up to 55 T with pulse duration of about 0.1 s in the temperature range 0.7-300 K.

Suski, W.; Palewski, T.; Nizhankovskii, V. I.; Klamut, J.

2006-11-01

15

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

16

Electric and Magnetic Fields Research and Public Information Dissemination Program annual report for fiscal year 1996  

SciTech Connect

The Electric and Magnetic Fields (EMF) Research and Public Information Dissemination (RAPID) Program was authorized by the Energy Policy Act of 1992 as a near-term effort to expand and accelerate the research needed to address the EMF issue. As required by this legislation, the EMF Interagency Committee, the National EMF Advisory Committee (NEMFAC), and the National Academy of Sciences (NAS) are providing valued input and advice for the direction of this program. With this input and advice, the Department of Energy (DOE) and the National Institute of Environmental Health Sciences (NIEHS) have developed and are implementing five-year program plans. Multi-year health effects research projects and related EMF measurement and exposure assessment projects are underway using funds appropriated in fiscal years 1994, 1995, and 1996 together with voluntary non-Federal contributions. The results of these research projects, along with the results of other EMF research, will be used as input to the hazard evaluation effort, which is the focus of the EMF RAPID Program. A coordinated interagency program is underway to communicate needed information on the EMF issue in a clear manner to the public and other decision makers.

NONE

1997-06-01

17

Research Directed Toward Understanding Behavior and Detection of Plasmas in Magnetic Field.  

National Technical Information Service (NTIS)

The goal of the experimental program was the boundary region between the physics of gaseous discharges and the physics of particle accelerators. A study was made of discharges with currents large enough for collective magnetic field effects to be prominen...

D. Finkelstein

1968-01-01

18

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

19

Research of the power frequency magnetic fields distribution around dry-type air-core reactor  

Microsoft Academic Search

The strong magnetic fields generated by reactors, which not only interfere other electric equipmentspsila regularly running, but also are potentially harmful to substation employeespsila health, are the main electromagnetic contamination in substations. In this paper, a mixed finite-element (FE) model for dry-type air-core reactor, which considers the effect of eddy current, is proposed for calculation of magnetic fields. According to

Zhang Yan; Wang Quandi; Li Bin; Zhao Yi; Liu Qingsheng; Hazem H. Refai

2008-01-01

20

Growth of pea epicotyl in low magnetic field implication for space research  

NASA Astrophysics Data System (ADS)

A magnetic field is an inescapable environmental factor for plants on the earth. However, its impact on plant growth is not well understood. In order to survey how magnetic fields affect plant, Alaska pea seedlings were incubated under low magnetic field (LMF) and also in the normal geo-magnetic environment. Two-day-old etiolated seedlings were incubated in a magnetic shield box and in a control box. Sedimentation of amyloplasts was examined in the epicotyls of seedlings grown under these two conditions. The elongation of epicotyls was promoted by LMF. Elongation was most prominent in the middle part of the epicotyls. Cell elongation and increased osmotic pressure of cell sap were found in the epidermal cells exposed to LMF. When the gravitational environment was 1G, the epicotyls incubated under both LMF and normal geomagnetic field grew straight upward and amyloplasts sedimented similarly. However, under simulated microgravity (clinostat), epicotyl and cell elongation was promoted. Furthermore, the epicotyls bent and amyloplasts were dispersed in the cells in simulated microgravity. The dispersion of amyloplasts may relate to the posture control in epicotyl growth under simulated microgravity generated by 3D clinorotation, since it was not observed under LMF in 1G. Since enhanced elongation of cells was commonly seen both at LMF and in simulated microgravity, all elongation on the 3D-clinostat could result from pseudo-low magnetic field, as a by-product of clinorotation. (i.e., clinostat results could be based on randomization of magnetic field together with randomization of gravity vector.) Our results point to the possible use of space for studies in magnetic biology. With space experiments, the effects of dominant environmental factors, such as gravity on plants, could be neutralized or controlled for to reveal magnetic effects more clearly.

Negishi, Y.; Hashimoto, A.; Tsushima, M.; Dobrota, C.; Yamashita, M.; Nakamura, T.

1999-01-01

21

Magnetic Fields Matter  

NSDL National Science Digital Library

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

VU Bioengineering RET Program, School of Engineering,

22

Magnetic Field Waves at Uranus.  

National Technical Information Service (NTIS)

The proposed research efforts funded by the UDAP grant to the BRI involve the study of magnetic field waves associated with the Uranian bow shock. This is a collaborative venture bringing together investigators at the BRI, Southwest Research Institute (Sw...

C. W. Smith M. L. Goldstein R. P. Lepping W. H. Mish H. K. Wong

1991-01-01

23

Magnetic field line Hamiltonian  

SciTech Connect

The basic properties of the Hamiltonian representation of magnetic fields in canonical form are reviewed. The theory of canonical magnetic perturbation theory is then developed and applied to the time evolution of a magnetic field embedded in a toroidal plasma. Finally, the extension of the energy principle to tearing modes, utilizing the magnetic field line Hamiltonian, is outlined.

Boozer, A.H.

1985-02-01

24

ASA conference on radiation and health: Health effects of electric and magnetic fields: Statistical support for research strategies. Final report  

SciTech Connect

This report is a collection of papers documenting presentations made at the VIII ASA (American Statistical Association) Conference on Radiation and Health entitled Health Effects of Electric and Magnetic Fields: Statistical Support for Research Strategies. Individual papers are abstracted and indexed for the database.

Not Available

1990-05-01

25

Research Directed Toward Understanding Behavior and Detection of Plasmas in Magnetic Field.  

National Technical Information Service (NTIS)

A summary is given of a study of the physics of high voltage, large current plasma discharges. Studied were discharges with currents large enough for magnetic field effects to be prominent (> 100,000 A) and voltages large enough for relativistic effects t...

D. Finkelstein

1968-01-01

26

Solar Magnetic Field  

NASA Astrophysics Data System (ADS)

Electrical currents flowing in the solar plasma generate a magnetic field, which is detected in the SOLAR ATMOSPHERE by spectroscopic and polarization measurements (SOLAR MAGNETIC FIELD: INFERENCE BY POLARIMETRY). The SOLAR WIND carries the magnetic field into interplanetary space where it can be measured directly by instruments on space probes....

Schüssler, M.; Murdin, P.

2000-11-01

27

Acquisition of High Field Nuclear Magnetic Resonance Spectrometers for Research in Molecular Structure, Function and Dynamics.  

National Technical Information Service (NTIS)

Two High-Field NMR spectrometers supported four research projects: Task 1, Mechanism of conversion of uridine to pseudouridine and to 4- thiouridine. We overexpressed the active C-terminal domain of enzyme Thil, required for 4-thiouridine modification of ...

G. Pack

2011-01-01

28

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

29

The Sun's global magnetic field.  

PubMed

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

Mackay, Duncan H

2012-07-13

30

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, André; Erdõs, Géza

2013-06-01

31

Magnetic Field Problem  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2007-03-03

32

Research Trends on Magnetic Bearings  

NASA Astrophysics Data System (ADS)

Use of magnetic bearings for high-speed rotor and application in clean environment or in special circumstance have been gradually increasing. This article overviews research trends and application presented before the Eighth International Symposium on Magnetic Bearings (ISMB-8). Interesting research topics are the combined realization of motor and magnetic bearing, low loss magnetic bearings and self-sensing techniques. New application fields include small spindles for data storage devices, energy storage flywheels, and artificial heart pumps. Various new technologies are reported related to these new application fields.

Okada, Yohji; Nonami, Kenzo

33

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

Most of the visible matter in the Universe is ionized so that cosmic magnetic fields are quite easy to generate and, due to the lack of magnetic monopoles, hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas, or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars, and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic field is still under debate. The available data for external galaxies can well be explained by field amplification and ordering via the dynamo mechanism. The measured field strengths and the similarity of field patterns and flow patterns of the diffuse ionized gas give strong indication that galactic magnetic fields are dynamically important. They may affect the formation of spiral arms, outflows, and the general evolution of galaxies. In spite of our increasing knowledge on magnetic fields, many important questions on the origin and evolution of magnetic fields, their first occurrence in young galaxies, or the existence of large-scale intergalactic fields remained unanswered. The present upgrades of existing instruments and several planned radio astronomy projects have defined cosmic magnetism as one of their key science projects.

Beck, Rainer; Wielebinski, Richard

34

Intergalactic magnetic fields  

Microsoft Academic Search

There is no observational support to the hypothesis of the most large-scale homogeneous magnetic field in the Universe. The best upper limit is given by interpretation of the Faraday rotation from the extragalactic radio sources. However the magnetic fields can be generated in the clusters of galaxies by a turbulence in the wakes of moving galaxies. These fields have an

A. A. Ruzmajkin

1991-01-01

35

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

36

Melatonin and magnetic fields.  

PubMed

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

Karasek, Michal; Lerchl, Alexander

2002-04-01

37

Magnetic field generator  

DOEpatents

A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.

Krienin, Frank (Shoreham, NY)

1990-01-01

38

On Cosmic Magnetic Fields  

NASA Astrophysics Data System (ADS)

Magnetic fields are present in all astrophysical media. However, many models and interpretations of observations often ignore them, because magnetic fields are difficult to handle and because they produce complicated morphological features. Here we will comment on the basic intuitive properties, which even if not completely true, provide a first guiding insight on the physics of a particular astrophysical problem. These magnetic properties are not mathematically demonstrated here. How magnetic fields evolve and how they introduce dynamical effects are considered, also including a short comment on General Relativity Magnetohydrodynamics. In a second part we consider some audacious and speculative matters. They are answers to three questions: a) How draw a cube without lifting the pencil from the paper so that when the pen passes through the same side do in the same direction? B) Are MILAGRO anisotropies miraculous? C) Do cosmic magnetic lenses exist?. The last two questions deal with issues related with the interplay between magnetic fields and cosmic ray propagation.

Florido, E.; Battaner, E.

2010-12-01

39

Magnetic fields at Uranus  

Microsoft Academic Search

The conclusions drawn regarding the structure, behavior and composition of the Uranian magnetic field and magnetosphere as revealed by Voyager 2 data are summarized. The planet had a bipolar magnetotail and a bow shock wave which was observed 23.7 Uranus radii (UR) upstream and a magnetopause at 18.0 UR. The magnetic field observed can be represented by a dipole offset

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

1986-01-01

40

THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

A new analysis of magnetic and concurrent plasma data collected from the ; space probes Pionecr 5, Explorer 10, and Mariner 2 yields a new model of the ; interplanetary magnetic field. It is hypothesized that the observed ; interplanetary field F\\/sub i\\/ is due to motion of the magnetometer relative to a ; negatively charged rotating sun from which

V. A. BAILEY

1963-01-01

41

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

42

The U-25B MHD-facility intended for research in strong electric and magnetic fields  

Microsoft Academic Search

The MHD electrical power generating system described in the present paper was developed for use in a Soviet-USA research program to be conducted during 1978 through 1982 to study such aspects of MHD electric power plants as long-term operation of circuit elements at high electric potentials; optimal designing of MHD elements for operation at electric fields as high as 3.5

V. A. Kirillin; A. E. Sheindlin; V. I. Maksimenko; S. A. Pashkov; D. S. Pinkhasik; S. I. Pishchikov; N. P. Privalov; V. D. Semenov; V. S. Sidorov; Iu. D. Sokirko

1978-01-01

43

Magnetic Field Waves at Uranus.  

National Technical Information Service (NTIS)

The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the phy...

C. W. Smith M. L. Goldstein R. P. Lepping W. H. Mish H. K. Wong

1994-01-01

44

Transmission line magnetic fields; Measurements and calculations  

Microsoft Academic Search

Recent controversy over 60 Hz magnetic fields has heightened public awareness of overhead transmission lines. As a result, there is increasing motivation to study the magnetic fields form transmission lines. The most cost effective means to conduct research into transmission line magnetic fields is with computer or reduced-scale line models. However, from the standpoint of public perception and acceptance, it

B. A. Clairmont; G. B. Johnson; J. H. Dunlap

1992-01-01

45

Directory of European Research Facilities for the Condensed Matter and Materials Sciences (Including High-Field Magnets, High-Flux Neutron Sources, Synchrotron Radiation Sources).  

National Technical Information Service (NTIS)

The directory provides information on the most important European laboratories performing research on condensed matter and materials using mainly high-field magnets, high-flux neutron sources and synchrotron radiation sources. It is intended to provide re...

D. L. Mitchell

1990-01-01

46

The First Magnetic Fields  

NASA Astrophysics Data System (ADS)

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars are discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.

Widrow, Lawrence M.; Ryu, Dongsu; Schleicher, Dominik R. G.; Subramanian, Kandaswamy; Tsagas, Christos G.; Treumann, Rudolf A.

2012-05-01

47

Magnetic Field Lines  

NSDL National Science Digital Library

This activity will introduce students to the idea of magnetic field lines--a concept they have probably encountered but may not fully grasp. Completing this activity and reading the corresponding background information should enable students to understand

Horton, Michael

2009-05-30

48

Magnetic field dosimeter development  

SciTech Connect

In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

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

1980-09-01

49

Magnetic field confinement for magnetically levitated vehicles  

SciTech Connect

A magnetically levitated vehicle adapted for movement along a guide way, comprising: a passenger compartment; first and second primary magnet means secured on the vehicle to produce a magnetic field having a magnetic flux density extending outward from the primary magnet means, to support the vehicle above and spaced from the guide way; and a plurality of confining magnets disposed on the vehicle to confine the magnetic flux extending outward from the primary magnet means and to reduce the strength of the primary magnetic field in the passenger compartment; wherein the primary magnet means has a capacity to produce a primary magnetic field having a maximum strength of at least 200 gauss in the passenger compartment, and the confining magnets maintain the strength of the primary magnetic field in the passenger compartment below 5 gauss.

Proise, M.

1993-05-25

50

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

51

Magnetic Multipole Field Model  

NSDL National Science Digital Library

The EJS Magnetic Multipole Field Model shows the field of a magnetic dipole or quadrupole with little compasses that indicate direction and relative field strength. A slider changes the angular orientation of the dipole and a movable compass shows the magnetic field direction and magnitude. Compass values can be recorded into a data table and analyzed using a built-in data analysis tool. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Magnetic Multipole 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_MagneticMultipoleField.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; Cox, Anne; Franciscouembre

2010-02-14

52

Magnetic Field Measurement System  

SciTech Connect

A magnetic field measurement system was designed, built and installed at MAX Lab, Sweden for the purpose of characterizing the magnetic field produced by Insertion Devices (see Figure 1). The measurement system consists of a large granite beam roughly 2 feet square and 14 feet long that has been polished beyond laboratory grade for flatness and straightness. The granite precision coupled with the design of the carriage yielded minimum position deviations as measured at the probe tip. The Hall probe data collection and compensation technique allows exceptional resolution and range while taking data on the fly to programmable sample spacing. Additional flip coil provides field integral data.

Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar [Advanced Design Consulting USA, 126 Ridge Road, P.O. Box 187, Lansing, NY 14882 (United States); Dunn, Jonathan Hunter [MAX-lab, SE-221 00 Lund (Sweden)

2007-01-19

53

Magnetic Field Problem: Current  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2007-03-03

54

Deformation of Water by a Magnetic Field  

ERIC Educational Resources Information Center

|After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

Chen, Zijun; Dahlberg, E. Dan

2011-01-01

55

Crustal magnetic field of Mars  

Microsoft Academic Search

The equivalent source dipole technique is used to model the three components of the Martian lithospheric magnetic field. We use magnetic field measurements made on board the Mars Global Surveyor spacecraft. Different input dipole meshes are presented and evaluated. Because there is no global, Earth-like, inducing magnetic field, the magnetization directions are solved for together with the magnetization intensity. A

B. Langlais; M. E. Purucker; M. Mandea

2004-01-01

56

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized emission traces turbulent fields which are strongest in spiral arms and bars (20-30 ?G) and in central starburst regions (50-100 ?G). Such fields are dynamically important, e.g. they can drive gas inflows in central regions. Polarized emission traces ordered fields which can be regular or anisotropic random, generated from isotropic random fields by compression or shear. The strongest ordered fields of 10-15 ?G strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several spiral galaxies reveal large-scale patterns, which are signatures of regular fields generated by a mean-field dynamo. However, in most spiral galaxies observed so far the field structure is more complicated. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Ordered magnetic fields are also observed in radio halos around edge-on galaxies, out to large distances from the plane, with X-shaped patterns. Future observations of polarized emission at high frequencies, with the EVLA, the SKA and its precursors, will trace galactic magnetic fields in unprecedented detail. Low-frequency telescopes (e.g. LOFAR and MWA) are ideal to search for diffuse emission and small RMs from weak interstellar and intergalactic fields.

Beck, Rainer

2012-05-01

57

The induced magnetic field.  

PubMed

Aromaticity is indispensable for explaining a variety of chemical behaviors, including reactivity, structural features, relative energetic stabilities, and spectroscopic properties. When interpreted as the spatial delocalization of ?-electrons, it represents the driving force for the stabilization of many planar molecular structures. A delocalized electron system is sensitive to an external magnetic field; it responds with an induced magnetic field having a particularly long range. The shape of the induced magnetic field reflects the size and strength of the system of delocalized electrons and can have a large influence on neighboring molecules. In 2004, we proposed using the induced magnetic field as a means of estimating the degree of electron delocalization and aromaticity in planar as well as in nonplanar molecules. We have since tested the method on aromatic, antiaromatic, and nonaromatic compounds, and a refinement now allows the individual treatment of core-, ?-, and ?-electrons. In this Account, we describe the use of the induced magnetic field as an analytical probe for electron delocalization and its application to a large series of uncommon molecules. The compounds include borazine; all-metal aromatic systems Al(4)(n-); molecular stars Si(5)Li(n)(6-n); electronically stabilized planar tetracoordinate carbon; planar hypercoordinate atoms inside boron wheels; and planar boron wheels with fluxional internal boron cluster moieties. In all cases, we have observed that planar structures show a high degree of electron delocalization in the ?-electrons and, in some examples, also in the ?-framework. Quantitatively, the induced magnetic field has contributions from the entire electronic system of a molecule, but at long range the contributions arising from the delocalized electronic ?-system dominate. The induced magnetic field can only indirectly be confirmed by experiment, for example, through intermolecular contributions to NMR chemical shifts. We show that calculating the induced field is a useful method for understanding any planar organic or inorganic system, as it corresponds to the intuitive Pople model for explaining the anomalous proton chemical shifts in aromatic molecules. Indeed, aromatic, antiaromatic, and nonaromatic molecules show differing responses to an external field; that is, they reduce, augment, or do not affect the external field at long range. The induced field can be dissected into different orbital contributions, in the same way that the nucleus-independent chemical shift or the shielding function can be separated into component contributions. The result is a versatile tool that is particularly useful in the analysis of planar, densely packed systems with strong orbital contributions directly atop individual atoms. PMID:21848282

Islas, Rafael; Heine, Thomas; Merino, Gabriel

2011-08-17

58

Photospheric and coronal magnetic fields  

SciTech Connect

Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. 101 refs.

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

1991-01-01

59

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

60

Magnetic field annihilators: invisible magnetization at the magnetic equator  

Microsoft Academic Search

Some distributions of magnetization give rise to magnetic fields that vanish everywhere above the surface, rendering these distributions of magnetization completely invisible. They are the annihilators of the magnetic inverse problem. Known examples are the infinite sheet with constant magnetization and the spherical shell of constant susceptibility magnetized by an arbitrary internal field. Here, we show that remarkably more interesting

S. Maus; V. Haak

2003-01-01

61

Status Report of Current Biological, Medical, and Engineering Research and Significant Study Results Regarding Potential Human Health Effects Associated with Power Frequency Electric and Magnetic Fields.  

National Technical Information Service (NTIS)

The report reviews planned and ongoing research on biological and health effects of 50- and 60-Hz electric and magnetic fields. The purpose of the report was to review results from research since May 1989 to determine new significant findings regarding po...

1990-01-01

62

Five years of magnetic field management  

SciTech Connect

The extensive publicity of epidemiological studies inferring correlation between 60 Hz magnetic fields and childhood leukemia prompted world wide research programs that have as a goal to determine if low frequency magnetic fields represent any risk for the general population, children or utility workers. While supporting this research effort through EPRI, Con Edison embarked on a technical research program aimed to: characterize magnetic fields as to intensity and variation in time; and investigate practical means to manage these magnetic fields through currently known methods. The final goal of these research projects is to establish viable methods to reduce magnetic field intensity to desired values at reasonable distances from the sources. This goal was pursued step by step, starting with an inventory of the main sources of magnetic fields in substations, distribution and transmission facilities and generating plants. The characterization of the sources helped to identify typical cases and select specific cases, far practical applications. The next step was to analyze the specific cases and develop design criteria for managing the magnetic fields in new installations. These criteria included physical arrangement of equipment based oil calculation of magnetic fields, cancellation effect, desired maximum field intensity at specific points and shielding with high magnetic permeability metals (mu-metal and steel). This paper summarizes the authors` experiences and shows the results of the specific projects completed in recent years.

Durkin, C.J.; Fogarty, R.P.; Halleran, T.M.; Mark, Dr. D.A.; Mukhopadhyay, A.

1995-01-01

63

Problems and priorities in epidemiologic research on human health effects related to wiring code and electric and magnetic fields.  

PubMed Central

Because of a reported excess of cancers among children living near power lines, there is some concern that electric and magnetic fields (EMFs) induced by electric power sources may affect human health, and this possibility has provoked considerable controversy. The scientific question of whether there are such health effects is far from resolved. Building upon a set of detailed reviews of the available evidence, this paper proposes research priorities and places particular emphasis on epidemiologic research. The most pressing need is to verify the validity of the claim that childhood cancer risk is affected by the type of wiring code in the vicinity of the household. More useful work can be done to verify this in the areas in which such studies have already been carried out, and additional studies should be done elsewhere. Methodological investigation of the interrelationships among different measures and proxies for EMF is needed, and this could feed back to influence the type of EMF measures used in epidemiologic studies. Studies of cancer among adults in relation to EMFs in the work place are needed. Of lower priority are studies of adverse reproductive outcomes in relation to parental EMF exposure and studies of the neurobehavioral impact of chronic EMF exposure. This article also discusses the structural impediments of conducting environmental epidemiology research and argues that bold, large-scale epidemiologic monitoring systems are needed. There is a discussion of the interface between epidemiology and public policy in a topic area as controversial as EMFs.

Siemiatycki, J

1993-01-01

64

Magnetic Field Measurements in Beam Guiding Magnets  

Microsoft Academic Search

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

K. N. Henrichsen

1998-01-01

65

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

66

Biological effects of high DC magnetic fields  

Microsoft Academic Search

The principal focus of the program is the analysis of magnetic field effects on physiological functions in experimental animals and selected organ and tissue systems. A major research effort has involved the use of electrical recording techniques to detect functional alterations in the cardiovascular, neural, and visual systems during the application of DC magnetic fields. These systems involve ionic conduction

Tenforde

1981-01-01

67

Static uniform magnetic fields and amoebae  

SciTech Connect

Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

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

1997-03-01

68

Magnetization reversal in ultrashort magnetic field pulses  

NASA Astrophysics Data System (ADS)

We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization reversal process. Comparing the case of perpendicular anisotropy with different kinds of in-plane anisotropies, a principal difference is found due to the symmetry of the shape anisotropy with respect to the anisotropy in question.

Bauer, M.; Lopusnik, R.; Fassbender, J.; Hillebrands, B.

2000-08-01

69

Magnetic Field Problem: Current and Magnets  

NSDL National Science Digital Library

The above animations represent two typical bar magnets each with a North and South pole. The arrows represent the direction of the magnetic field. A wire is placed between the magnets and a current that comes out of the page can be turned on.

Christian, Wolfgang; Belloni, Mario

2007-03-03

70

Magnetic Field Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil

Labros Spiridon Petropoulos

1993-01-01

71

Integrated semiconductor magnetic field sensors  

Microsoft Academic Search

Recent developments in integrated silicon magnetic devices are reviewed, with particular attention given to integrated Hall plates, magnetic field-effect transistors, vertical and lateral bipolar magnetotransistors, magnetodiodes, and current-domain magnetometers. Also described are current developments in integrated magnetic field sensors based on III-V semiconductors and bulk Hall-effect devices. The discussion also covers magnetic device modeling and the incorporation of magnetic devices

H. P. Baltes; R. S. Popovic

1986-01-01

72

Planetary magnetic fields  

NASA Astrophysics Data System (ADS)

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 radial extent. The relevant electrical conductivities range from metallic values to values that may be only about 1% or less that of a typical metal, appropriate to ionic fluids and semiconductors. In all planets, the Coriolis force is dynamically important, but slow rotation may be more favorable for a dynamo than fast rotation. The maintenance and persistence of convection appears to be easy in gas giants and ice-rich giants, but is not assured in terrestrial planets because the quite high electrical conductivity of iron-rich cores guarantees a high thermal conductivity (through the Wiedemann-Franz law), which allows for a large core heat flow by conduction alone. In this sense, high electrical conductivity is unfavorable for a dynamo in a metallic core. Planetary dynamos mostly appear to operate with an internal field ~(2??/?)1/2 where ? is the fluid density, ? is the planetary rotation rate and ? is the conductivity (SI units). Earth, Ganymede, Jupiter, Saturn, Uranus, Neptune, and maybe Mercury have dynamos, Mars has large remanent magnetism from an ancient dynamo, and the Moon might also require an ancient dynamo. Venus is devoid of a detectable global field but may have had a dynamo in the past. The presence or absence of a dynamo in a terrestrial body (including Ganymede) appears to depend mainly on the thermal histories and energy sources of these bodies, especially the convective state of the silicate mantle and the existence and history of a growing inner solid core. Induced fields observed in Europa and Callisto indicate the strong likelihood of water oceans in these bodies.

Stevenson, David J.

2003-03-01

73

Planetary Magnetic Fields and Climate Evolution  

NASA Astrophysics Data System (ADS)

In this presentation we review the ways in which the presence (or absence) of a planetary magnetic field can influence climate, and provide specific examples using Earth, Venus, Mars, and Titan. We then identify future needs in this research area.

Brain, D. A.; Leblanc, F.; Luhmann, J. G.; Moore, T. E.; Tian, F.

2012-06-01

74

'High magnetic fields in the USA'.  

National Technical Information Service (NTIS)

During the past thirty years research using high magnetic fields has technically evolved in the manner, but not the magnitude, of the so-called big science areas of particle physics, plasma physics, neutron scattering, synchrotron light scattering, and as...

L. J. Campbell D. M. Parkin J. E. Crow H. J. Schneider-Muntau N. S. Sullivan

1994-01-01

75

Magnetic Analysis in Metallurgical Research.  

National Technical Information Service (NTIS)

The subject of magnetic analysis in metallurgical research has been reviewed selectively in the following areas of materials technological research: (1) iron and iron base alloys, (2) nickel-iron alloys, (3) alnico permanent magnet alloys, (4) rare-earth ...

C. Domenicali E. Kneller J. D. Blades V. V. Damiano

1967-01-01

76

Tracing magnetic fields with ground state alignment  

NASA Astrophysics Data System (ADS)

Observational studies of magnetic fields are vital as magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g. transport of heat), and cosmic rays. The existing ways of magnetic field studies have their limitations. Therefore, it is important to explore new effects that can bring information about magnetic field. We identified a process “ground state alignment” as a new way to determine the magnetic field direction in diffuse medium. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The alignment is due to anisotropic radiation impinging on the atom/ion, while the magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields (1G?B?10-15G). Compared to the upper level Hanle effect, atomic realignment is most suitable for the studies of magnetic field in the diffuse medium, where magnetic field is relatively weak. The corresponding physics of alignment is based on solid foundations of quantum electrodynamics and in a different physical regime the alignment has become a part of solar spectroscopy. In fact, the effects of atomic/ionic alignment, including the realignment in magnetic field, were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. It is very encouraging that a variety of atoms with fine or hyperfine splitting of the ground or metastable states exhibit the alignment and the resulting polarization degree in some cases exceeds 20%. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this paper, we shall review the basic physical processes involved in atomic realignment. We shall also discuss its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields, including those in the early universe.

Yan, Huirong; Lazarian, A.

2012-08-01

77

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

Goren, Y.; Mahale, N.K.

1996-08-06

78

Evolution of twisted magnetic fields  

SciTech Connect

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

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

1985-02-01

79

Development of superconductors for applications in high-field, high-current-density magnets for fusion research  

SciTech Connect

The development of large-bore, high-field magnets for fusion energy applications requires a system approach to both magnet and conductor design. At Lawrence Livermore National Laboratory (LLNL), the criteria used to choose superconductors include: strain tolerance, radiation tolerance, heat removal, stability, fabricability, and cost. We report on the performance of industrially produced, prototype, Ti-modified Nb/sub 3/Sn wires developed with LLNL support. Wire performance characteristics evaluated include critical current as a function of magnetic field, temperature, and applied strain. Tests were performed to determine how this performance translates to the performance of a cable-in-conduit conductor system using this wire. An alternative to Nb/sub 3/Sn superconductors is NbN, which is strain and radiation insensitive. We report preliminary efforts to produce multifilamentary NbN conductors by liquid-metal infiltration of NbN-coated, high-strength fibers. In addition, we discuss the fabrication of multifilamentary NbN conductors and their possible impact on magnet design.

Summers, L.T.; Miller, J.R.

1986-09-26

80

Stellar atmospheres with magnetic field  

Microsoft Academic Search

It is proposed that the most probable configuration of the magnetic field in the atmosphere of an Ap star is an almost force-free, poloidal field, close to a low-order multipole. Such a magnetic field can not change the structure of the atmosphere to any great extent, but the vertical component of the Lorentz force can decrease the effective gravity by

K. Stepien

1980-01-01

81

Microprobe for Measuring Magnetic Fields  

Microsoft Academic Search

The Hall effect has been widely utilized to measure magnetic fields. The relatively simple geometry of a Hall element suggested the use of such a device on a microscale as a probe to examine magnetic fields of small structures. Hall probes are described which were constructed with a sensitive area about 10×10 ?. Fields of less than 0.01 gauss were

D. D. Roshon Jr.

1962-01-01

82

Magnetic fields in galactic jets  

Microsoft Academic Search

The jet region of M87 is discussed to illustrate the astrophysical observations of radio sources, with note made of magnetic field phenomena contributing to radio frequency emissions. The jet appearing in M87 has been modelled as a continuous supersonic flow of plasma embedded in a self-consistent, ordered magnetic field. The field has both parallel and helical components, and may work

A. Ferrari

1982-01-01

83

Protogalactic evolution and magnetic fields  

Microsoft Academic Search

We show that the relatively strong magnetic fields ($\\\\ge 1 \\\\mu$G) in high\\u000aredshift objects can be explained by the combined action of an evolving\\u000aprotogalactic fluctuation and electrodynamic processes providing the magnetic\\u000aseed fields. Three different seed field mechanisms are reviewed and\\u000aincorporated into a spherical \\

Harald Lesch; Masashi Chiba

1994-01-01

84

Protogalactic evolution and magnetic fields  

Microsoft Academic Search

We show that the relatively strong magnetic fields (>=1muG) in high redshift objects can be explained by the combined action of an evolving protogalactic fluctuation and electrodynamic processes providing the magnetic seed fields. Three different seed field mechanisms are reviewed and incorporated into a spherical \\

H. Lesch; M. Chiba

1995-01-01

85

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

86

The National High Magnetic Field Laboratory: Condensed Matter Science in Continuous Magnetic Fields  

Microsoft Academic Search

The National High Magnetic Field Laboratory (NHMFL) operates three facilities in support of magnet-related research. The main facilities are located at Florida State University, Tallahassee, Florida, the ultra-low-temperature high-magnetic-field facilities are located at the University of Florida, Gainesville, Florida, and the pulsed field facilities are located at the Los Alamos National Laboratory, Los Alamos, New Mexico. These facilities support a

M. D. Bird; J. E. Crow; P. Schlottmann

2003-01-01

87

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

88

Characteristic Lengths of Magnetic Field in Magnetohydrodynamic Turbulence  

Microsoft Academic Search

In the framework of turbulence dynamo, flow motions amplify a weak seed magnetic field through the stretching of field lines. Although the amplification process has been a topic of active research, less attention has been paid to the length scales of magnetic field. In this Letter, we describe a numerical study on characteristic lengths of magnetic field in magnetohydrodynamic turbulence.

Jungyeon Cho; Dongsu Ryu

2009-01-01

89

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.

90

Microwave Measurements of Coronal Magnetic Field  

Microsoft Academic Search

Magnetic field measurements of the solar corona using microwave observation are reviewed. The solar corona is filled with highly ionised plasma and magnetic field. Moving charged particles interact with magnetic field due to Lorentz force. This results in gyration motion perpendicular to the magnetic field and free motion along the magnetic field. Circularly polarized electro-magnetic waves interact with gyrating electrons

K. Shibasaki

2006-01-01

91

Magnetic Field of Mars  

NASA Astrophysics Data System (ADS)

An internal potential function was created using the averaged MGS vector data released by Mario Acuna for altitudes from 95 to 209 km above the Martian geoid, all longitudes, and latitudes from 87 degrees south to 78 degrees north. Even with some gaps in coverage it is found that a consistent internal potential function can be derived up to spherical harmonic terms of n = 65 using all three components of the data. Weighting the data according to the standard errors given, the model fits to 7-8 nT rms. The energy density spectrum of the harmonics is seen to peak near n = 39 with a value of 7 J/cu km and fall off to less than 0.5 J/cu km below n = 15 and above n = 55. Contour maps of the X (north) component drawn for 100 km altitude show the strongly anomalous region centered at 60 degrees S latitude and 180 degrees longitude, as well as the alternating east-west trends already observed by other groups. Maps of the other components show the anomalous region, but not the east-west trends. The dichotomy is also maintained with much weaker anomalies bounding the northern plains. The results herein as as well as those of others is limited by the sparse low-altitude data coverage as well as the accuracy of the observations in the face of significant spacecraft fields. Work by Connerney and Acuna have mitigated these sources somewhat, but the design of the spacecraft did not lend itself to accurate observations. Recent results reported by David Mitchell of the ER group have shown that the field observations are significantly influenced by the solar wind with the possibility that the present results may only reflect that portion of the internal field visible above 95 km altitude. Depending on the solar wind, the anomaly field may be shielded or distorted to produce spurious results. The spectrum we have obtained so far may only see the stronger portion of the signal with a significant weaker component hidden. Measurements of crustal anomalies versus relative ages of source bodies combined with later absolute dating of Martian geologic units could lead to a quantitative constraint on the thermal history of the planet, i.e. the time when convective dynamo generation ceased in the core. Determination of directions of magnetization of anomaly sources as a function of age combined with the expectation that the Martian dynamo field was roughly aligned with the rotation axis would lead to a means of investigating polar wandering for Mars. Preliminary analysis of two magnetic anomalies in the northern polar region has yielded paleomagnetic pole positions near 50 N, 135 W, about 30 degrees north of Olympus Mons. This location is roughly consistent with the orientation of the planet expected theoretically prior to the formation of the Tharsis region. In the future, more accurate observations of the vector field at the lowest possible altitudes would significantly improve our understanding of Martian thermal history, polar wandering, and upper crustal evolution. Mapping potential resources (e.g., iron-rich source bodies) for future practical use would also be a side benefit. Additional information is contained in the original abstract.

Cain, J. C.; Ferguson, B.; Mozzoni, D.; Hood, L.

2000-07-01

92

Evolution of primordial magnetic fields  

NASA Astrophysics Data System (ADS)

Here we briefly summarise the main phases which determine the dynamical evolution of primordial magnetic fields in the early universe. On the one hand, strong fields undergo damping due to excitations of plasma fluctuations, and, on the other hand, weak magnetic fields will be strongly amplified by the small-scale dynamo in a turbulent environment. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10-13-10-11 G on comparatively small scales 100 pc -10 kpc may survive to prior to structure formation. Additionally, any weak magnetic field will be exponentially amplified during the collapse of the first minihalos until they reach equipartition with the turbulent kinetic energy. Hence, we argue that it seems possible for cluster magnetic fields to be entirely of primordial origin.

Banerjee, R.

2013-06-01

93

Cosmic Magnetic Fields - An Overview  

NASA Astrophysics Data System (ADS)

Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds' staffs get at times “glued” to a stone, a alodestone. In Europe the magnetic compass came through the Arab sailors who met the Portuguese explorers. The first scientific treatise on magnetism, “De Magnete”, was published by William Gilbert who in 1600 described his experiments and suggested that the Earth was a huge magnet. Johannes Kepler was a correspondent of Gilbert and at times suggested that planetary motion was due to magnetic forces. Alas, this concept was demolished by Isaac Newton,who seeing the falling apple decided that gravity was enough. This concept of dealing with gravitational forces only remains en vogue even today. The explanations why magnetic effects must be neglected go from “magnetic energy is only 1% of gravitation” to “magnetic fields only complicate the beautiful computer solutions”. What is disregarded is the fact that magnetic effects are very directional(not omni-directional as gravity) and also the fact that magnetic fields are seen every where in our cosmic universe.

Wielebinski, Richard; Beck, Rainer

94

Measurements of magnetic field alignment  

SciTech Connect

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

Kuchnir, M.; Schmidt, E.E.

1987-11-06

95

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 few×10(-12)??G if the energy scale of inflation is few×10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields. PMID:23971556

Campanelli, Leonardo

2013-08-06

96

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

97

Field Directed Ordering in Magnetic Nanocrystal Structures  

NASA Astrophysics Data System (ADS)

Iron oxide nanocrystals (NCs) have been the focus of intense research owing to the observation of tunable magnetic properties which could lead to advances in many fields including magnetic storage devices and medicine. We have been targeting the use of iron oxide NCs as magnetoresistance (MR) based sensors using ordered NC arrays. In this work, we will present our efforts toward using external magnetic fields to induce intraparticle ordering in iron oxide NC drop cast films. We use x-ray diffraction to analyze effects of the external fields on the NC array structure, while using SQUID magnetometry to probe the effects of NC interactions on the magnetic properties of iron oxide NCs ranging from 5 - 20 nm in diameter. MR measurements suggest large changes in the MR ratio can be achieved using the directed ordering approach for NC arrays. Our work could provide new avenues towards the fabrication of new magnetic devices.

Lawson, Stuart; Meulenberg, Robert

2013-03-01

98

Magnetic field in a finite toroidal domain  

SciTech Connect

The magnetic field structure in a domain surrounded by a closed toroidal magnetic surface is analyzed. It is shown that ergodization of magnetic field lines is possible even in a regular field configuration (with nonvanishing toroidal component). A unified approach is used to describe magnetic fields with nested toroidal (possibly asymmetric) flux surfaces, magnetic islands, and ergodic field lines.

Ilgisonis, V. I.; Skovoroda, A. A., E-mail: skovorod@nfi.kiae.r [Russian Research Centre Kurchatov Institute (Russian Federation)

2010-05-15

99

Study on Accurate 3D Magnetic Field Measurement System  

Microsoft Academic Search

The existed magnetic field measurement systems have some shortcomings just as poor accuracy and automation. Most of them can only achieve one or two dimensions' measurement. The research of accurate 3D magnetic field measurement system is introduced. The 3D magnetic field sensor is made by six Hall devices which are attached to six surfaces of a cube respectively. The output

Chen Dixiang; Pan Mengchun; Luo Feilu

2007-01-01

100

Magnetic fields and scintillator performance  

SciTech Connect

Experimental data have shown that the light output of a scintillator depends on the magnitude of the externally applied magnetic fields, and that this variation can affect the calorimeter calibration and possibly resolution. The goal of the measurements presented here is to study the light yield of scintillators in high magnetic fields in conditions that are similar to those anticipated for the LHC CMS detector. Two independent measurements were performed, the first at Fermilab and the second at the National High Magnetic Field Laboratory at Florida State University.

Green, D.; Ronzhin, A. [Fermi National Accelerator Lab., Batavia, IL (United States); Hagopian, V. [Florida State Univ., Tallahasse, FL (United States)

1995-06-01

101

Magnetic field structure of Mercury  

NASA Astrophysics Data System (ADS)

Recently planet Mercury—an unexplored territory in our solar system—has been of much interest to the scientific community due to recent flybys of the spacecraft MESSENGER that discovered its intrinsic stationary and large-scale dipole like magnetic field structure with an intensity of ˜300nT confirming Mariner 10 observations. In the present study, with the observed constraint of Mercury's atmospheric magnetic field structure, internal magnetic field structure is modeled as a solution of magnetic diffusion equation. In this study, Mercury's internal structure mainly consists of a stable stratified fluid core and the convective mantle. For simplicity, magnetic diffusivity in both parts of the structure is considered to be uniform and constant with a value represented by a suitable averages. It is further assumed that vigorous convection in the mantle disposes of the electric currents leading to a very high diffusivity in that region. Thus, in order to satisfy observed atmospheric magnetic field structure, Mercury's most likely magnetic field structure consists of a solution of MHD diffusion equation in the core and a combined multipolar (dipole and quadrupole like magnetic field structures embedded in the uniform field) solution of a current free like magnetic field structure in the mantle and in the atmosphere. With imposition of appropriate boundary conditions at the core-mantle boundary for the first two diffusion eigen modes, in order to satisfy the observed field structure, present study puts the constraint on Mercury's core radius to be ˜2000km.From the estimated magnetic diffusivity and the core radius, it is also possible to estimate the two diffusion eigen modes with their diffusion time scales of ˜8.6 and 3.7 billion years respectively suggesting that the planet inherits its present-day magnetic field structure from the solar Nebula. It is proposed that permanency of such a large-scale magnetic field structure of the planet is attained during Mercury's early evolutionary history of heavy bombardments by the asteroids and comets supporting the giant impact hypothesis for the formation of Mercury.

Hiremath, K. M.

2012-04-01

102

Cosmic Magnetic Fields – An Overview  

Microsoft Academic Search

\\u000a Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion\\u000a on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys\\u000a of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds’ staffs get at times

Richard Wielebinski; Rainer Beck

2010-01-01

103

Magnetic Pumping in Spatially Inhomogeneous Magnetic Fields.  

National Technical Information Service (NTIS)

Magnetic pumping by major-radius oscillation of a toroidal plasma can be made more practical by introducing a major-radius range within which the vertical-field gradient is sufficiently great so that major-radius perturbations are marginally stable or, be...

H. P. Furth R. A. Ellis

1972-01-01

104

Simulations of Photospheric Magnetic Fields  

Microsoft Academic Search

We have run plots of artificial data, which mimic solar magnetograms, through standard algorithms to critique several results reported in the literature. In studying correlation algorithms, we show that the differences in the profiles for the differential rotation of the photospheric magnetic field stem from different methods of averaging. We verify that the lifetimes of small magnetic features, or of

A. A. Smith; H. B. Snodgrass

1999-01-01

105

Measuring Earth's Magnetic Field Simply.  

ERIC Educational Resources Information Center

|Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)|

Stewart, Gay B.

2000-01-01

106

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

107

Thermometers in Low Magnetic Fields  

Microsoft Academic Search

In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of\\u000a a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and\\u000a type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four\\u000a different baths were used for temperatures

G. Gersak; S. Begus

2010-01-01

108

Heavy fermions in high magnetic fields  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The National High Magnetic Field Laboratory (NHMFL) has established major new facilities at LANL. This project sought to explore some exciting new problems in condensed matter physics that could be studied using these facilities. We studied the behavior of heavy-fermion compounds in high-magnetic fields. The unusual properties of these materials are governed by small energy scales arising from strong many-body correlations, demonstrating that the fields that can be achieved in the NHMFL can be used to probe these correlations.

Trugman, S.; Bedell, K.; Bonca, J.; Gulacsi, M. [Los Alamos National Lab., NM (United States); Yu, C. [California Univ., Irvine, CA (United States)

1996-05-01

109

Theorem on magnet fringe field  

SciTech Connect

Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iB{sub x} = {summation}(b{sub n} + ia{sub n})(x + iy){sup n}, where x, y, and z denote horizontal, vertical, and longitudinal (along the magnet) coordinates. Since the magnet length L is necessarily finite, deflections are actually proportional to ``field integrals`` such as {bar B}L {equivalent_to} {integral} B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For {bar a}{sub n}, {bar b}{sub n}, {bar B}{sub x}, and {bar B}{sub y} defined this way, the same expansion Eq. 1 is valid and the ``standard`` approximation is to neglect any deflections not described by this expansion, in spite of the fact that Maxwell`s equations demand the presence of longitudinal field components at the magnet ends. The purpose of this note is to provide a semi-quantitative estimate of the importance of {vert_bar}{Delta}p{sub {proportional_to}}{vert_bar}, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to {vert_bar}{Delta}p{sub 0}{vert_bar}, the total deflection produced by passage through the whole magnet. To emphasize the generality and simplicity of the result it is given in the form of a theorem. The essence of the proof is an evaluation of the contribution of the longitudinal field B{sub x} from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Talman, R. [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies

1995-12-31

110

Astrophysical Magnetic Fields and Topics in Galaxy Formation.  

National Technical Information Service (NTIS)

The grant was used to support theoretical research on a variety of astro-physical topics falling broadly into those described by the proposal: galaxy formation, astrophysical magnetic fields, magnetized accretion disks in AGN, new physics, and other astro...

G. B. Field

1997-01-01

111

Quantitative review of human susceptibility to magnetic fields  

Microsoft Academic Search

Research into the effects of magnetic fields on humans and animals is sparse. Much of it lacks quantification of exposure time to the fields by the subjects. The importance of some parameters has not yet been ascertained, such as the distinction between uniform and gradient fields. Also, orientation between subjects and the magnetic fields is seldom reported. The information available

Schiff

1978-01-01

112

High field magnetic resonance  

US Patent & Trademark Office Database

A magnetic resonance system is disclosed. The system includes a transceiver having a multichannel receiver and a multichannel transmitter, where each channel of the transmitter is configured for independent selection of frequency, phase, time, space, and magnitude, and each channel of the receiver is configured for independent selection of space, time, frequency, phase and gain. The system also includes a magnetic resonance coil having a plurality of current elements, with each element coupled in one to one relation with a channel of the receiver and a channel of the transmitter. The system further includes a processor coupled to the transceiver, such that the processor is configured to execute instructions to control a current in each element and to perform a non-linear algorithm to shim the coil.

2010-09-21

113

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.  

SciTech Connect

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

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

2004-10-03

114

Magnetic fields in neutron stars  

NASA Astrophysics Data System (ADS)

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

Viganò, Daniele

2013-09-01

115

Geomorphology Field Research Project  

NSDL National Science Digital Library

The goal of this research project is to allow students to integrate and apply their geomorphic knowledge in a comprehensive study of a local landscape system. In this project, students investigate the origin and significance of a series of flat-topped mesas and isolated hills that rise above the gently sloping surface of alluvial fans along the San Gabriel Mountain foothills. Students work as part of a research team of 3 or 4 members. Each team is assigned a different field area and conduct a comprehensive geomorphic investigation of landforms within that area. Team members are expected to work collaboratively to formulate a research plan, complete a background literature search, and conduct independent fieldwork outside of class time. Each team divides up responsibilities as they see fit. At the end of the quarter, each team presents the results of their research in an oral presentation in front of the class, and in a professional written report submitted to the professor. Designed for a geomorphology course

Marshall, Jeffrey S.

116

Black holes and magnetic fields  

NASA Astrophysics Data System (ADS)

The exact mechanism of formation of highly relativistic jets from galactic nuclei and microquasars remains unknown but most accepted models involve a central black hole and a strong external magnetic field. This idea is based on assumption that the black hole rotates and the magnetic field threads its horizon. Magnetic torques provide a link between the hole and the surrounding plasma which then becomes accelerated. We first review our work on black holes immersed in external stationary vacuum (electro)magnetic fields in both test-field approximation and within exact general-relativistic solutions. A special attention will be paid to the Meissner-type effect of the expulsion of the flux of external axisymmetric stationary fields across rotating (or charged) black holes when they approach extremal states. This is a potential threat to any electromagnetic mechanism launching the jets at the account of black-hole rotation because it inhibits the extraction of black-hole rotational energy. We show that the otherwise very useful "membrane viewpoint of black holes" advocated by Thorne, Price and Macdonald does not represent an adequate formalism in the context of the field expulsion from extreme black holes. After briefly summarizing the results for black holes in magnetic fields in higher dimensions - the expulsion of stationary axisymmetric fields was demonstrated to occur also for extremal black-hole solutions in string theory and Kaluza-Klein theory - we shall review astrophysically relevant axisymmetric numerical simulations reported recently by Gammie, Komissarov, Krolik and others. Although the field expulsion has not yet been observed in these time-dependent simulations, they may still be too far away from the extreme limit at which the black-hole Meissner effect should show up. We mention some open problems which, according to our view, deserve further investigation.

Bi?ák, Ji?í; Karas, Vladimír; Ledvinka, Tomáš

2007-04-01

117

Simulations of magnetic fields in the cosmos  

Microsoft Academic Search

The origin of large-scale magnetic fields in clusters of galaxies remains controversial. The intergalactic magnetic field within filaments should be less polluted by magnetised outflows from active galaxies than magnetic fields in clusters. Therefore, filaments may be a better laboratory to study magnetic field amplification by structure formation than galaxy clusters, which typically host many more active galaxies. We present

M. Brüggen; M. Hoeft

2006-01-01

118

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

119

HMI Magnetic Field Data Products  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory (SDO) spacecraft will begin observing the solar photospheric magnetic field continuously after commissioning in early 2009. This paper describes the HMI magnetic processing pipeline and the expected data products that will be available. The full disk line-of-sight magnetic field will be available every minute with 1" resolution. Comparable vector measurements collected over a three-minute time interval will ordinarily be averaged for at least 10 minutes before inversion. Useful Quick Look products for forecasting purposes will be available a few minutes after observation. Final products will be computed within 36 hours and made available through the SDO Joint Science Operations Center (JSOC). Three kinds of magnetic data products have been defined - standard, on-demand, and on-request. Standard products, such as frequently updated synoptic charts, are made all the time on a fixed cadence. On-demand products, such as high cadence full-disk disambiguated vector magnetograms, will be generated whenever a user asks for them. On-request products, such as high-resolution time series of MHD model solutions, will be generated as resources allow. This paper describes the observations, magnetograms, synoptic and synchronic products, and field model calculations that will be produced by the HMI magnetic pipeline.

Hoeksema, J.; Hmi, M. T.

2008-05-01

120

Tunneling in a magnetic field  

SciTech Connect

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

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

2006-05-15

121

Thermalization in external magnetic field  

NASA Astrophysics Data System (ADS)

In the AdS/CFT framework meson thermalization in the presence of a constant external magnetic field in a strongly coupled gauge theory has been studied. In the gravitational description the thermalization of mesons corresponds to the horizon formation on the flavour D7-brane which is embedded in the AdS 5 × S 5 background in the probe limit. The apparent horizon forms due to the time-dependent change in the baryon number chemical potential, the injection of baryons in the gauge theory. We will numerically show that the thermalization happens even faster in the presence of the magnetic field on the probe brane. We observe that this reduction in the thermalization time sustains up to a specific value of the magnetic field.

Ali-Akbari, Mohammad; Ebrahim, Hajar

2013-03-01

122

Photospheric Magnetic Field: Quiet Sun  

NASA Astrophysics Data System (ADS)

The solar photosphere is the layer in which the magnetic field has been most reliably and most often measured. Zeeman- and Hanle-effect based probes have revealed many details of a rich variety of structures and dynamic processes, but the number of open and debated questions has remained large. The magnetic field in the quiet Sun has maintained a particularly large number of secrets and has been a topic of a particularly lively debate as new observations and analysis techniques have revealed new and often unexpected aspects of its organization, physical structure and origin.

Solanki, S. K.

2009-06-01

123

Effect of Crossed Magnetic Field on Ozone Production in Air  

Microsoft Academic Search

An application of magnetic field, B to a discharge chamber under transverse electric field, E is studied, with the objective to view the effect of magnetic field to the electrons in a plasma. Theory of gas discharge stated that this configuration will create a helical motion to electrons due to gradient drift or gyration. Experimental result from previous research showed,

Z. Buntat; I. R. Smith; N. A. M. Razali

2009-01-01

124

Engaging Teachers and Students in Solar Research: How do Sunspots Evolve? Studying the Morphology and Magnetic Field Strength of Sunspots Over Time  

NASA Astrophysics Data System (ADS)

Astronomy Research Based Science Education (A-RBSE) is a multi-year teacher professional development program sponsored by NSF and administered through the National Optical Astronomy Observatory (NOAO). The program reaches the formal education community through a national audience of well-trained high-school teachers. Every year, a new cohort of teachers prepare for research through an on-line course in the spring. In the summer they conduct astronomy research at NOAO, working with astronomer-mentors to gather and analyze their data. They then return to their classrooms and engage their students in inquiry-based astronomy research using this authentic data. Solar is one of five research areas in the A-RBSE program. Maps of magnetic field strength around active regions are taken with the National Solar Observatory (NSO) McMath-Pierce telescope using 1.565 um, g=3 (Zeeman split) Fe I spectral lines. The field strengths are then compared with the sunspots' sizes over time. The NSO IR Array Camera and Infrared Adaptive Optics are used with the telescope's Main Spectrograph. Data have been taken about twice yearly since 2003. A-RBSE teachers travel to the telescope and participate in the data collection as part of the summer research course. At other times of the year, veteran A-RBSE teachers plus a couple of their students can propose for more telescope time for data collection. Once in the classroom, after analyzing the data, students have often compared the magnetograms, Dopplergrams and intensitygrams to glean a more in-depth model of the morphology and environment of active regions. Presentations on their solar research have been made at science fairs, NSTA, AAS, ASP and AGU meetings. Student and teacher have also published their results in the RBSE Journal. The poster presentation will elucidate on the IR solar database and software used in the A-RBSE program. For more information, visit http://www.noao.edu/education/arbse/.

Walker, Constance E.; Pichotta, J.; Plymate, C.; Stobie, E.

2008-05-01

125

Magnetic Field from Loops Model  

NSDL National Science Digital Library

The EJSMagnetic Field from Loops model computes the B-field created by an electric current through a straight wire, a closed loop, and a solenoid. Users can adjust the vertical position of the slice through the 3D field. The Magnetic Field from Loops 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_ntnu_MagneticFielfFromLoops.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 for classical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Hwang, Fu-Kwun

2008-11-17

126

Magnetic field generation in Galactic molecular clouds  

NASA Astrophysics Data System (ADS)

We investigate the magnetic field which is generated by turbulent motions of a weakly ionized gas. Galactic molecular clouds give us an example of such a medium. As in the Kazantsev-Kraichnan model we assume a medium to be homogeneous and a neutral gas velocity field to be isotropic and ? correlated in time. We take into consideration the presence of a mean magnetic field, which defines a preferred direction in space and eliminates isotropy of magnetic field correlators. Evolution equations for the anisotropic correlation function are derived. Isotropic cases with zero mean magnetic field as well as with small mean magnetic field are investigated. It is shown that stationary bounded solutions exist only in the presence of the mean magnetic field for the Kolmogorov neutral gas turbulence. The dependence of the magnetic field fluctuations amplitude on the mean field is calculated. The stationary anisotropic solution for the magnetic turbulence is also obtained for large values of the mean magnetic field.

Istomin, Ya. N.; Kiselev, A.

2013-10-01

127

FIELD CHARACTERIZATION OF XFEL QUADRUPOLE MAGNETS  

Microsoft Academic Search

A rotating coil setup for magnetic field characterization and fiducialization of XFEL quadrupole magnets is pre- sented. The instrument allows measurement of the rel- ative position of the magnetic axis with accuracy better than 1 ?m and measurement of weak magnetic error field components. Tests and evaluation based on a FLASH quadrupole magnet are presented together with a discus- sion

A. Hedqvist; H. Danared; F. Hellberg; J. Pfluger

128

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

129

Magnetic fields in extragalactic jets  

Microsoft Academic Search

Observations indicate that jets (i.e., charged particle beams) are emitted from the central black hole sources of active galactic nuclei and quasars. Magnetic fields are produced in e(-)-p or e(-)-e(+)-p jets when electrons (and positrons) are slowed with respect to protons in the jets. Interaction with an ambient interstellar gas or external radiation field can cause such drift velocities. Calculations

William K. Rose

1987-01-01

130

Magnetic fields in extragalactic jets  

Microsoft Academic Search

Observations indicate that jets are emitted from the central black hole sources of active galactic nuclei and quasars. Magnetic fields are produced in e--p or e--e+-p jets when electrons and positrons are slowed with respect to protons in the jets. Interaction with an ambient interstellar gas or external radiation field can cause such drift velocities. In this paper calculations for

William K. Rose

1987-01-01

131

The somatosensory evoked magnetic fields  

Microsoft Academic Search

Averaged magnetoencephalography (MEG) following somatosensory stimulation, somatosensory evoked magnetic field(s) (SEF), in humans are reviewed. The equivalent current dipole(s) (ECD) of the primary and the following middle-latency components of SEF following electrical stimulation within 80–100 ms are estimated in area 3b of the primary somatosensory cortex (SI), the posterior bank of the central sulcus, in the hemisphere contralateral to the

Ryusuke Kakigi; Minoru Hoshiyama; Motoko Shimojo; Daisuke Naka; Hiroshi Yamasaki; Shoko Watanabe; Jing Xiang; Kazuaki Maeda; Khanh Lam; Kazuya Itomi; Akinori Nakamura

2000-01-01

132

Magnetic Field Issues in Magnetic Resonance Imaging.  

NASA Astrophysics Data System (ADS)

Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil have been presented. Also, the design of a self-shielded cylindrical gradient coil with a restricted length has been presented. In order to generate gradient coils adequate for head imaging without including the human shoulders in the design, asymmetric cylindrical coils in which the gradient center is shifted axially towards the end of a finite cylinder have been introduced and theoretical as well as experimental results have been presented. In order to eliminate eddy current effects in the design of the non-shielded asymmetric gradient coils, the self-shielded asymmetric cylindrical gradient coil geometry has been introduced. Continuing the development of novel geometries for the gradient coils, the complete set of self-shielded cylindrical gradient coils, which are designed such that the x component of the magnetic field varies linearly along the three traditional gradient axes, has been presented. In order to understand the behavior of the rf field inside a dielectric object, a mathematical model is briefly presented. Although specific methods can provide an indication of the rf behavior inside a loosely dielectric object, finite element methodology is the ultimate approach for modeling the human torso and generating an accurate picture for the shape of the rf field inside this dielectric object. For this purpose we have developed a 3D finite element model, using the Coulomb gauge condition as a constraint. Agreement with the heterogeneous multilayer planar model has been established, while agreement with theoretical results from the spherical model and experimental results from the cylindrical model at 170 M H z is very good and provides an encouraging sign for using this finite element approach for modeling the rf inside the human body. (Abstract shortened by UMI.).

Petropoulos, Labros Spiridon

133

Advances in Magnetic Field Sensors  

Microsoft Academic Search

The most important milestone in the field of magnetic sensors was when AMR sensors started to replace Hall sensors in many applications where the greater sensitivity of AMRs was an advantage. GMR and SDT sensors finally found applications. We also review the development of miniaturization of fluxgate sensors and refer briefly to SQUIDs, resonant sensors, GMIs, and magnetomechanical sensors.

Pavel Ripka; Michal Janosek

2010-01-01

134

Random Field Effect in Magnets.  

National Technical Information Service (NTIS)

In order to explore the consequences of random field effects we have carried out a series of neutron scattering experiments on three prototypical diluted Ising magnets. The systems studied are Rb sub 2 Co sub 7 Mg sub 3 F sub 4 which is a model two dimens...

R. J. Birgeneau

1982-01-01

135

The Effect of Varying Magnetic Field Gradient on Combustion Dynamic  

NASA Astrophysics Data System (ADS)

The focus of the recent experimental research is to provide control of the combustion dynamics and complex measurements (flame temperature, heat production rate, and composition of polluting emissions) for pelletized wood biomass using a non-uniform magnetic field that produces magnetic force interacting with magnetic moment of paramagnetic oxygen. The experimental results have shown that a gradient magnetic field provides enhanced mixing of the flame compounds by increasing combustion efficiency and enhancing the burnout of volatiles.

Suzdalenko, Vera; Zake, Maija; Barmina, Inesa; Gedrovics, Martins

2011-01-01

136

Interaction Mechanisms, Biological Effects and Biomedical Applications of Static and Extremely-Low-Frequency Magnetic Fields.  

National Technical Information Service (NTIS)

A major stimulus for research on the bioeffects of static magnetic fields has been the effort to develop technologies for energy production and storage that utilize intense magnetic fields. In addition, the rapid emergence of magnetic resonance imaging as...

T. S. Tenforde

1986-01-01

137

NMR imaging in the earth's magnetic field.  

PubMed

The most important and very expensive part of a magnetic resonance imaging set-up is the magnet, which is capable of generating a constant and highly homogeneous magnetic field. Here a new MR imaging technique without the magnet is introduced. This technique uses the earth's magnetic field instead of a magnetic field created by a magnet. This new method has not yet reached the stage of medical application, but the first images obtained by MRIE (magnetic resonance imaging in the earth's field) show that the resolution is close to that expected based on sensitivity estimations. PMID:2233218

Stepisnik, J; Erzen, V; Kos, M

1990-09-01

138

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

139

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

140

Active Region Magnetic Fields. I. Plage Fields  

NASA Astrophysics Data System (ADS)

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 orientation, and f = 15%. At disk center, there is a component of weak (<1000 G), more horizontal fields that corresponds to arching field lines connecting footpoints of different polarities. The center-to-limb variation (CLV) of the field strength shows that, close to the limb ( mu = 0.3), the field strength is reduced to 800 G from its disk-center value. This can be interpreted as a gradient of B with height in solar plages of around -3 G km-1. From this CLV study, we also deduce that magnetic field lines remain vertical for the entire range of heights involved. A similar analysis is performed for structures found in active regions that show a continuous distribution of azimuths (resembling sunspots) but that do not have a darkening in continuum. These "azimuth centers" show slightly larger values of B than normal plages, in particular at their magnetic center. Filling factors are also larger on average for these structures. The velocities in the magnetic component of active regions have been studied for both averaged Stokes profiles over the entire active region and for the spatially resolved data. The averaged profiles (more representative of high filling factor regions) do not show any significant mean velocities. However, the spatial average of Doppler velocities derived from the spatially resolved profiles (i.e., unweighted by filling factor) show a net redshift at disk center of 200 m s-1. The spatially resolved velocities show a strong dependence on filling factor. Both mean velocities and standard deviations are reduced when the filling factor increases. This is interpreted as a reduction of the p-mode amplitude within the magnetic component. Strong evidence for velocities transverse to the magnetic field lines has been found. Typical rms values are between 200 and 300 m s-1, depending on the filling factor. The possible importance of these transverse motions for the dynamics of the upper atmospheric layers is discussed. The asymmetries of the Stokes profiles and their CLV have been studied. The averaged Stokes V profiles show amplitude and area asymmetries that are positive at disk center and become negative at the limb. Both asymmetries, and for the two Fe I lines, are maximized away from disk center. The spatially resolved amplitude asymmetries show a clear dependence on filling factor: the larger the filling factor, the smaller the amplitude asymmetry. On the other hand, the area asymmetry is almost independent of the filling factor. The only observed dependence is the existence of negative area-asymmetry profiles at disk center for filling factors smaller than 0.2. Around 20% of the observed points in a given plage have negative area asymmetry. The amplitude asymmetry of Stokes V is, on the other hand, always positive. The amplitude asymmetries of the linear polarization profiles are observed to have the same sign as the Stokes V profiles. Similarly, the same CLV variation of the linear polarization amplitude asymmetries as for Stokes V has been found. The scenarios in which this similarity can exist are studied in some detail.

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

1997-01-01

141

Electron dynamics in inhomogeneous magnetic fields.  

PubMed

This review explores the dynamics of two-dimensional electrons in magnetic potentials that vary on scales smaller than the mean free path. The physics of microscopically inhomogeneous magnetic fields relates to important fundamental problems in the fractional quantum Hall effect, superconductivity, spintronics and graphene physics and spins out promising applications which will be described here. After introducing the initial work done on electron localization in random magnetic fields, the experimental methods for fabricating magnetic potentials are presented. Drift-diffusion phenomena are then described, which include commensurability oscillations, magnetic channelling, resistance resonance effects and magnetic dots. We then review quantum phenomena in magnetic potentials including magnetic quantum wires, magnetic minibands in superlattices, rectification by snake states, quantum tunnelling and Klein tunnelling. The third part is devoted to spintronics in inhomogeneous magnetic fields. This covers spin filtering by magnetic field gradients and circular magnetic fields, electrically induced spin resonance, spin resonance fluorescence and coherent spin manipulation. PMID:21393794

Nogaret, Alain

2010-06-04

142

Magnetic fields in the cosmos  

SciTech Connect

Although only a small part of available energy in the universe is invested in magnetic fields, they are responsible for most of the continual violent activity in the cosmos. There is a single, generic explanation for the ability of bodies as different as a dense, cold planet and a tenuous hot galactic disk to generate a magnetic field. The explanation, first worked out for the earth, comes from the discipline of magnetohydrodynamics. The cosmos is filled with fluids capable of carrying electric currents. The magnetic fields entrained in these fluids are stretched and folded by the fluid motion, gaining energy in the process. In other words, the turbulent fluids function as dynamos. However, the dynamo mechanism by itself cannot account for the exceptionally strong field of some stars. Because of such gaps in information, the rival hypothesis that there are primordial fields cannot be disproved. The balance of evidence, however, indicates that the planets, sun, most stars and the galaxy function as colossal dynamos. (SC)

Parker, E.N.

1983-08-01

143

Field-Induced Magnetic Phenomena in Molecule-Based Magnets  

NASA Astrophysics Data System (ADS)

Understanding the relationship between the crystal structure and magnetic ordering is crucial for the design of three-dimensional molecule-based magnets with high ordering temperatures. In this talk, we introduce a novel series of molecule-based magnets consisting of transition metal ions (Mn, Fe, Co, Ni or Cu) coordinated with the organic ligand dicyanamide [N(CN)_2]^-.(J.L. Manson et al. al.), Chem. Mater. 10, 2552 (1998); S.R. Batten et al. al., Chem. Commun. (Cambridge) 1998, 439; M. Kurmoo et al. al., New J. Chem. 22, 1515 (1998). The crystal structures for all compounds are isomorphous in the paramagnetic regime as well as in the ordered state. However, the compounds with transition metal ions having six or less electrons in the 3d orbitals order as canted antiferromagnets (AFM) while the ones with seven or more electrons order as ferromagnets (FM). The spin orientation is nearly in perpendicular directions for the AFM versus FM systems.(C.R. Kmety et al. al.), Phys. Rev. B 60, 60 (1999).^,(C.R. Kmety et al. al.), Phys. Rev. B 62, 5576 (2000). An external magnetic field induces a spin rotation transition in the Mn compound and an energy-level crossing for the Fe compound.(C.R. Kmety and A.J. Epstein, National High Magnetic Field Laboratory 2000 Annual Research Review.) The possible origins of the variability of the magnetic structure for the first row transition metal ions compounds will be discussed.

Kmety, Carmen R.

2001-03-01

144

Behavior of magnetic liquids in an inhomogeneous magnetic field  

SciTech Connect

The authors present experimental results from the investigation of the behavior of certain magnetic liquids differeing in the degree of stability in inhomogenous magnetic fields. The growth of holding presure of sealing step at rest is reviewed and the increase of effective viscosity in inhomogeneous magnetic fields is studied. The behaviors of magnetic liquids in an inhomogeneous magnetic field are sensitive to structural changes caused by the field. Significant differences are demonstrated between magnetic liquids with the same saturation magnetization but different particle size distribution.

Anton, I.; Bika, D.; Potents, I.; Vekash, L.

1986-01-01

145

Equivalent source mapping of lunar magnetic field  

NASA Astrophysics Data System (ADS)

JAXA (Japan Aerospace Exploration Agency) shall launch the SELENE (SELenological and ENgineering Explorer) spacecraft this autumn. Amongst many instruments, it has a magnetometer (LMAG: Lunar MAGnetomter) which will measure the magnetic field on the orbit around the Moon. The nominal orbit of the SELENE is about 100km in altitudes for 1 year observation. Although the extended mission is still not determined, LMAG team is requesting a low altitude (less than 50km) observation, if the remaining fuel allows. We are preparing data processing software for the mission. Here, we report an objective scheme for mapping the lunar crustal magnetic field from the orbital measurement data of unequal altitudes. In this study, the magnetic field is restored by solving a linear inverse-problem determining the sources distributed on the lunar surface to satisfy the observational data, which is known as the equivalent source method. Our scheme has three features improving the method: First, the source calculation is performed simultaneously with detrending. Second, magnetic charges (magnetic monopoles) are used as the equivalent sources. It reduces the density of the sources for the same smoothness in produced field, comparing to the dipole sauces. Third, the number of sources is taken large enough to avoid the problem of configuration of the sources, instead the damped least square assuming the strength of each charge is similar to the next one, and the smoothness factor is determined by minimizing Akaike's Bayesian Information Criterion (ABIC). It guarantees the objectivity of the calculation, in other words, there is no adjustable parameter which may depend of the researcher dealing the data analyses. For testing the scheme, we apply this method to the Lunar Prospector magnetometer data, and provide magnetic field map in the region centered at several regions of strong crustal field including the Reiner Gamma anomaly. The stability of the method and the resolution of the anomaly map are found to be satisfactory.

Toyoshima, M.; Shibuya, H.

2007-12-01

146

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

147

SQUID-Detected Magnetic Resonance Imaging in Microtesla Magnetic Fields  

Microsoft Academic Search

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc

R. McDermott; N. Kelso; S. K. Lee; M. MöBetale; M. Mück; W. Myers; B. ten Haken; H. C. Seton; A. H. Trabesinger; A. Pines; J. Clarke

2004-01-01

148

Two dimensional frustrated magnets in high magnetic field  

Microsoft Academic Search

Frustrated magnets in high magnetic field have a long history of offering beautiful surprises to the patient investigator. Here we present the results of extensive classical Monte Carlo simulations of a variety of models of two dimensional magnets in magnetic field, together with complementary spin wave analysis. Striking results include (i) a massively enhanced magnetocaloric effect in antiferromagnets bordering on

L. Seabra; N. Shannon; P. Sindzingre; T. Momoi; B. Schmidt; P. Thalmeier

2009-01-01

149

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

150

Undergraduates and Field Research Concepts.  

ERIC Educational Resources Information Center

|Describes a course (with a framework loosely based on the environmental impact statement) in which students learn research methods as they cooperate in interdisciplinary field research projects. Includes a rationale for the course, a generalized outline of field experiences, and examples of student projects (both on-campus briefings and field…

Marotz, Glen A.; And Others

1986-01-01

151

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

152

Magnetic field of atrial depolarization.  

PubMed

The isomagnetic maps of normal subjects and patients with right and left atrial overloading were recorded to determine the characteristic features of the magnetic field of atrial depolarization. The isomagnetic maps examined in this study indicated the instantaneous current source, which specifically localizes the current sources due to the right and left atria, respectively. The magnetic field recorded with a second derivative gradiometer clearly detected the cardiac current source from the right atrium, which is located close to the anterior chest wall, thus this method improved the diagnostic sensitivity for right atrial overloading. In patients with left atrial overloading, the isomagnetic map showed multiple dipoles due to the right and left atria, respectively, which are difficult to be detected by the electrocardiogram or isopotential map. These results suggest that the magnetocardiogram provides useful information on the current source to supplement information obtained by the conventional electrocardiogram. PMID:2978585

Takeuchi, A; Watanabe, K; Katayama, M; Nomura, M; Nakaya, Y; Mori, H

153

FOREWORD: Focus on Materials Analysis and Processing in Magnetic Fields Focus on Materials Analysis and Processing in Magnetic Fields  

NASA Astrophysics Data System (ADS)

Recently, interest in the applications of feeble (diamagnetic and paramagnetic) magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan. Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3), which was held on 14-16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields. This focus issue compiles 13 key papers selected from the proceedings of MAP3. Other papers of the proceedings are published in Journal of Physics: Conference Series. Tournier and Beaugnon review experimental texturing in metallic melts by cooling in magnetic fields, which is modeled in detail in a study by Tournier. Wang et al provide further experimental results on the solidification of Mn-90.4 wt % Sb alloy in magnetic fields. The orientations of grains and particles induced by magnetic fields is reported by Horii et al (rare-earth-doped cuprates), Tanaka et al (barium-bismuth titanate ceramics), Liu and Schwartz (Bi2Sr2CaCu2Ox/AgMg wires) and Tsuda and Sakka (carbon nanotubes). Gielen et al present a model of how to quantify a molecular alignment using magnetic birefringence, and Ando et al simulate the movement of feeble particles in magnetic fields. Hirota et al report the experimental control of the lattice constant in a triangular lattice of feeble magnetic particles. The size separation of diamagnetic particles by magnetic fields is experimentally studied by Tarn et al and theoretically studied by Fukui et al. A setup measuring x-ray diffraction patterns in magnetic fields up to 5 T and temperatures above 200 oC has been developed by Mitsui et al. We hope that this focus issue will help readers to understand several aspects of materials analysis and processing in magnetic fields at the frontier of the science.

Sakka, Yoshio; Hirota, Noriyuki; Horii, Shigeru; Ando, Tsutomu

2009-03-01

154

Anisotropic Magnetism in Field-Structured Composites  

SciTech Connect

Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.

Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

1999-06-24

155

Studies on Somatosensory Evoked Magnetic Fields.  

National Technical Information Service (NTIS)

Spatiotemporal patterns of somatosensory evoked magnetic fields to stimulation of upper and lower limb nerves were examined in healthy humans. The studies summarized here provide the first magnetic field maps over the primary foot projection area after li...

J. Huttunen

1987-01-01

156

Luminescence in applied magnetic fields  

NASA Astrophysics Data System (ADS)

Metal complexes and solids were synthesized and subjected to photoexcitation measurements under the influence of externally applied magnetic fields. The photoluminescence of complexes of rhodium (I) and iridium (I) displayed both field induced emission bands and a many fold shortening of the excited state lifetime. Both the decay rates and the induced emission band intensities showed a quadratic dependence on the applied field. A several fold shortening of the phosphorescence from the octaphosphitoplatinum (II) anion under an applied field (50 T) was also observed. Spectroscopic studies of several bis (N-heterocyclic) complexes of copper (I) were also concluded and complete group theoretic assignments of the charge transfer excited states were made. The technique of Thermal Modulation was perfected and applied to the study of the exited states of transition metal complexes with near degenerate emitting states.

Crosby, G. A.

1989-08-01

157

Simulations of Photospheric Magnetic Fields  

NASA Astrophysics Data System (ADS)

We have run plots of artificial data, which mimic solar magnetograms, through standard algorithms to critique several results reported in the literature. In studying correlation algorithms, we show that the differences in the profiles for the differential rotation of the photospheric magnetic field stem from different methods of averaging. We verify that the lifetimes of small magnetic features, or of small patterns of these features in the large-scale background field, are on the order of months, rather than a few days. We also show that a meridional flow which is cycle dependent creates an artifact in the correlation-determined magnetic rotation which looks like a torsional oscillation; and we compare this artifact to the torsional patterns that have been reported. Finally, we simulate the time development of a large-scale background field created solely from an input of artifical, finite-lifetime 'sunspot' bipoles. In this simulation, we separately examine the effects of differential rotation, meridional flow and Brownian motion (random walk, which we use rather than diffusion), and the inclination angles of the sunspot bipoles (Joy's law). We find, concurring with surface transport equation models, that a critical factor for producing the patterns seen on the Sun is the inclination angle of the bipolar active regions. This work was supported by NSF grant 9416999.

Smith, A. A.; Snodgrass, H. B.

1999-05-01

158

Field Weakening of Permanent Magnet Machines - Design Approaches  

Microsoft Academic Search

Permanent Magnet (PM) machines have been developed for numerous applications due to their attractive features especially after the development of NdFeB magnets. However, their complicated control lets the researchers develop new machine structures with easy field control. New alternative PM machine topologies with field weakening or hybrid excitation have been introduced in the literature for years to eliminate the effects

T. A. Lipo; M. Aydin

159

Field Concentrator Based Resonant Magnetic Sensor  

Microsoft Academic Search

A novel resonant magnetic sensor based on the combination of a mechanical resonator and a magnetic field concentrator with two gaps is reported. In contrast to previous Lorentz force based resonant magnetic sensors, a high sensitivity is achieved without modulated driving current and complex feedback electronics. Furthermore, compared to magnetic moment based resonant magnetic sensors, the new concept requires no

S. Brugger; P. Simon; O. Paul

2006-01-01

160

Color Superconducting Matter in a Magnetic Field  

SciTech Connect

We investigate the effect of a magnetic field on cold dense quark matter using an effective model with four-Fermi interactions. We find that the gap parameters representing the predominant pairing between the different quark flavors show oscillatory behavior as a function of the magnetic field. We point out that due to electric and color neutrality constraints the magnetic fields as strong as presumably existing inside magnetars might induce significant deviations from the gap structure at a zero magnetic field.

Fukushima, Kenji [RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973 (United States); Warringa, Harmen J. [Department of Physics, Bldg. 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2008-01-25

161

Numerical Simulation In Magnetic Drug Targeting. Magnetic Field Source Optimization  

Microsoft Academic Search

\\u000a This paper presents numerical simulation model and results on magnetic drug targeting therapy. The study aims at investigating\\u000a the aggregate blood - magnetic carrier flow interaction with an external magnetic field. Another objective was finding the\\u000a optimal magnetic field source configuration that provides for flows that best assist in magnetic drug targeting. In order\\u000a to evaluate the effects we used

A. Dobre; A. M. Morega

162

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the field gradients estimated from the magnetizing field strengths used in the encoding process. .

Lo, C. C. H.; Leib, J.; Jiles, D. C.; Chedister, W. C.

2002-05-01

163

Radiative transfer in very strong magnetic fields  

NASA Astrophysics Data System (ADS)

The study of the cooling of neutron stars has been undertaken by many researchers in the past twenty-five years, but this study has been made difficult by the inherent theoretical and observational uncertainties; most observations of their thermal X-ray flux have yielded only upper limits. More sensitive satellites such as ROSAT and AXAF may provide more positive flux information, and it is important to know how to interpret these data in terms of surface temperature. One of the most important factors in this interpretation is the effect of the surface magnetic field.Young neutron stars are believed to have extremely strong magnetic fields, on the order of 10(12)G. These fields dominate the physics of the atmosphere. In particular, atoms in the atmospheres of neutron stars have much greater binding energies than in the zero-field case, and they are constrained to move along the field lines. We use a multiconfigurational Hartree-Fock code, modified for very strong magnetic fields, to calculate wavefunctions, energies and oscillator strengths for several atoms in representative values of the magnetic field.We then use these simulations to construct model atmospheres for neutron stars. Because of the low mass necessary for optical depth unity in the soft X-rays (typically [...]) and because of the short time scale for gravitational separation (~ 1 - 100s), the photosphere is likely to consist of a pure element. Numerous processes could cause many elements to be important, so we investigate atmospheres consisting of pure hydrogen, helium, carbon, nitrogen and silicon in magnetic fields of 9.4 x 10(11)G, 2.35 x 10(12)G, and 4.7 x 10(12)G.We also use the high-field energies to investigate soft X-ray lines in gamma-ray bursts. Highly ionized elements could create absorption lines in the 1-15keV range, and the identification of such lines in conjunction with cyclotron lines would determine the magnetic field and gravitational redshift on the surface of the star, which would provide clues to the equation of state on the interior. We conclude with a discussion of the prospect of identifying these lines with future satellites.

Miller, Michael Coleman

164

Magnetic fields in the early Universe  

Microsoft Academic Search

This review concerns the origin and the possible effects of magnetic fields in the early Universe. We start by providing the reader with a short overview of the current state of the art of observations of cosmic magnetic fields. We then illustrate the arguments in favor of a primordial origin of magnetic fields in the galaxies and in the clusters

Dario Grasso; Hector R. Rubinstein

2001-01-01

165

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

166

Penetration of plasma across a magnetic field  

NASA Astrophysics Data System (ADS)

Experiments were performed at the Nevada Terawatt Facility to investigate the plasma penetration across an externally applied magnetic field. In experiment, a short-pulse laser ablates a polyethylene laser target, producing a plasma which interacts with an external magnetic field. The mechanism which allows the plasma to penetrate the applied magnetic field in experiment will be discussed.

Plechaty, C.; Presura, R.; Wright, S.; Neff, S.; Haboub, A.

2009-08-01

167

Magnetic field reversals in the Milky Way  

Microsoft Academic Search

Radio observations of nearby spiral galaxies have tremendously enhanced our knowledge of their global magnetic field distributions. Recent theoretical developments in the area of dynamos have also helped in the interpretation of magnetic field data in spiral galaxies. When it comes to the magnetic field in the Milky Way galaxy, our position in the Milky Way's galactic disk hinders our

J. P. Vallee

1996-01-01

168

Primordial magnetic field limits from cosmological data  

NASA Astrophysics Data System (ADS)

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; Tevzadze, Alexander G.; Sethi, Shiv K.; Pandey, Kanhaiya; Ratra, Bharat

2010-10-01

169

Evolution of normal pulsar magnetic fields  

NASA Astrophysics Data System (ADS)

Results and new progress of the origin and evolution of pulsar magnetic fields are reviewed. Lots of models about how such strong magnetic fields were generated, mainly two kinds of structures were proposed for initial magnetic fields: fields confined in the cores and fields confined in the crusts of neutron stars. No consensus has been reached on whether the magnetic fields decay or not, despite some observational evidence for the evolution of magnetic fields. The discrepancy between characteristic ages and kinematic ages indicates that the magnetic fields decay exponentially. On the other hand, the braking indices of several young pulsars and the comparison between pulsar characteristic ages and the ages of associated supernova remnants suggest that the magnetic fields of young pulsars grow like a power-law. Pulsar population synthesis is one of the most important methods to investigate the evolution of magnetic fields. Many simulations show that if magnetic fields do decay exponentially, the e-folding decay time should be 100 Myr or longer. The numerical calculations of the Ohmic decay in the crust indicate that the scenario of exponential decay is oversimple, and the evolution could be divided into four possible phases approximately: exponential decay, no decay, power-law decay and exponential decay again. The model of magnetic fields expulsion induced by spin-down suggests that the magnetic fields decay only in a period between 107yr and 108yr.

Sun, Xiaohui; Han, Jinlin

2002-06-01

170

Research in Rice Fields  

USGS Publications Warehouse

Between 1987 and 1999, 2.4-3 million acres of rice were planted annually nationwide. Rice fields are a major component of the contemporary landscapes in the Gulf Coastal Plain, the Mississippi Alluvial Valley, and Central Valley of California. In 1998, approximately 600,000 acres of rice were planted in Louisiana. In the Louisiana plant commodities report for 1998, total value for rice was over $350 million; sugarcane was the only plant commodity that exceeded this value. Louisiana has over 2,000 rice farmers supporting over 12,000 jobs in the state. Rice fields in the United States receive high use by wildlife, especially shorebirds, wading birds, and waterfowl. Waterbirds use rice fields for food, shelter, and breeding habitat.

Geological Survey (U.S.)

2000-01-01

171

Crustal Magnetic Fields of Terrestrial Planets  

NASA Astrophysics Data System (ADS)

Magnetic field measurements are very valuable, as they provide constraints on the interior of the telluric planets and Moon. The Earth possesses a planetary scale magnetic field, generated in the conductive and convective outer core. This global magnetic field is superimposed on the magnetic field generated by the rocks of the crust, of induced (i.e. aligned on the current main field) or remanent (i.e. aligned on the past magnetic field). The crustal magnetic field on the Earth is very small scale, reflecting the processes (internal or external) that shaped the Earth. At spacecraft altitude, it reaches an amplitude of about 20 nT. Mars, on the contrary, lacks today a magnetic field of core origin. Instead, there is only a remanent magnetic field, which is one to two orders of magnitude larger than the terrestrial one at spacecraft altitude. The heterogeneous distribution of the Martian magnetic anomalies reflects the processes that built the Martian crust, dominated by igneous and cratering processes. These latter processes seem to be the driving ones in building the lunar magnetic field. As Mars, the Moon has no core-generated magnetic field. Crustal magnetic features are very weak, reaching only 30 nT at 30-km altitude. Their distribution is heterogeneous too, but the most intense anomalies are located at the antipodes of the largest impact basins. The picture is completed with Mercury, which seems to possess an Earth-like, global magnetic field, which however is weaker than expected. Magnetic exploration of Mercury is underway, and will possibly allow the Hermean crustal field to be characterized. This paper presents recent advances in our understanding and interpretation of the crustal magnetic field of the telluric planets and Moon.

Langlais, Benoit; Lesur, Vincent; Purucker, Michael E.; Connerney, Jack E. P.; Mandea, Mioara

2010-05-01

172

Nuclear magnetic resonance apparatus for pulsed high magnetic fields  

NASA Astrophysics Data System (ADS)

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.

Meier, Benno; Kohlrautz, Jonas; Haase, Jürgen; Braun, Marco; Wolff-Fabris, Frederik; Kampert, Erik; Herrmannsdörfer, Thomas; Wosnitza, Joachim

2012-08-01

173

Near Field Spectroscopy of Quantum Dots Under Magnetic Field  

Microsoft Academic Search

We present the basic steps for the study of the linear near field absorption spectra of semiconductor quantum dots under magnetic field of variable orientation. We show that the application of the magnetic field alone is sufficient to induce -increasing the spot illuminated by the near field probe- interesting features to the absorption spectra.

Anna Zora; Constantinos Simserides; Georgios Triberis

2005-01-01

174

Near Field Spectroscopy of Quantum Dots Under Magnetic Field  

Microsoft Academic Search

We present the basic steps for the study of the linear near field absorption spectra of semiconductor quantum dots under magnetic field of variable orientation. We show that the application of the magnetic field alone is sufficient to induce -increasing the spot illuminated by the near field probe- interesting features to the absorption spectra.

Anna Zora; Constantinos Simserides; Georgios Triberis

2004-01-01

175

The origins of lunar crustal magnetic fields  

NASA Astrophysics Data System (ADS)

This thesis is devoted to understanding the origins of lunar crustal magnetism. We wish to understand the processes which have created and modified the crustal magnetic field distribution that we observe today, and to determine whether the Moon ever had an active magnetohydrodynamic dynamo. Previously, our only measurements of lunar magnetic fields came from the Explorer 35 and Apollo missions. Data coverage was incomplete, but sufficient to establish some systematics of the crustal field distribution. With new data from the Magnetometer and Electron Reflectometer instrument on Lunar Prospector, we have generated the first completely global maps of the lunar crustal fields. We use measurements of electrons magnetically reflected above the lunar surface, which we then correct for the effects of electrostatic fields (which also reflect electrons), and convert to estimates of surface magnetic fields. The resulting global map shows that impact basins and craters (especially the youngest) generally have low magnetic fields, suggesting impact demagnetization, primarily by shock effects. A secondary signature of some large lunar basins (especially older ones) is the presence of a more localized central magnetic anomaly. Meanwhile, the largest regions of strong crustal fields lie antipodal to young large impact basins, suggesting shock remanent magnetization due to a combination of antipodal focussing of seismic energy and/or ejecta and plasma compression of ambient magnetic fields. Smaller regions of strong magnetic fields are sometimes associated with basin ejecta, and basin and crater ejecta terranes have the strongest average fields outside of the antipodal regions. This implies that impact-generated magnetization may extend beyond the antipodal regions. The antipodal, non-antipodal, and central basin magnetic fields, as well as returned samples, can all be used to estimate the lunar magnetic field history and place constraints on a possible lunar dynamo. All of these quantities provide evidence for stronger magnetic fields early in the Moon's history, and thereby suggest the existence of an ancient core dynamo.

Halekas, Jasper S.

176

Magnetic field observations in Comet Halley's coma  

NASA Astrophysics Data System (ADS)

During the encounter with Comet Halley, the magnetometer (MISCHA) aboard the Vega 1 spacecraft observed an increased level of magnetic field turbulence, resulting from an upstream bow wave. Both Vega spacecraft measured a peak field strength of 70-80 nT and observed draping of magnetic field lines around the cometary obstacle. An unexpected rotation of the magnetic field vector was observed, which may reflect either penetration of magnetic field lines into a diffuse layer related to the contact surface separating the solar-wind and cometary plasma, or the persistence of pre-existing interplanetary field structures.

Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.

1986-05-01

177

Magnetic field seeding by galactic winds  

Microsoft Academic Search

The origin of intergalactic magnetic fields is still a mystery and several scenarios have been proposed so far: among them, primordial phase transitions, structure-formation shocks and galactic outflows. In this work, we investigate how efficiently galactic winds can provide an intense and widespread `seed' magnetization. This may be used to explain the magnetic fields observed today in clusters of galaxies

Serena Bertone; Corina Vogt; Torsten Enßlin

2006-01-01

178

Invited Safety of Strong, Static Magnetic Fields  

Microsoft Academic Search

Issues associated with the exposure of patients to strong, static magnetic fields during magnetic resonance imaging (MRI) are reviewed and discussed. The history of human exposure to magnetic fields is reviewed, and the contra- dictory nature of the literature regarding effects on human health is described. In the absence of ferromagnetic for- eign bodies, there is no replicated scientific study

John F. Schenck

2000-01-01

179

Intergalactic Magnetic Fields from Quasar Outflows  

Microsoft Academic Search

Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function of size and magnetic field strength at different redshifts. We generically find that by a redshift z~3,

Steven R. Furlanetto; Abraham Loeb

2001-01-01

180

Magnetic fields in Local Group dwarf irregulars  

Microsoft Academic Search

Aims: We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods: We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m

K. T. Chyzy; M. Wezgowiec; R. Beck; D. J. Bomans

2011-01-01

181

Baking a magnetic-field display  

NASA Astrophysics Data System (ADS)

Copy machine developer powder is an alternative for creating permanent displays of magnetic fields. A thin layer of developer powder on a sheet of paper placed over a magnet can be baked in the oven, producing a lasting image of a magnetic field.

Cavanaugh, Terence; Cavanaugh, Catherine

1998-02-01

182

Exploring Magnetic Fields with a Compass  

ERIC Educational Resources Information Center

|A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In…

Lunk, Brandon; Beichner, Robert

2011-01-01

183

Cluster magnetic fields from galactic outflows  

Microsoft Academic Search

We performed cosmological, magnetohydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields is galactic outflows during the starburst phase of galactic evolution. To do this, we coupled a semi-analytical model for magnetized galactic winds as suggested by Bertone, Vogt & Enßlin to our cosmological simulation. We

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

2009-01-01

184

Sub arcsec evolution of solar magnetic fields  

Microsoft Academic Search

Context: .The evolution of the concentrated magnetic field in flux tubes is one challenge of the nowadays Solar physics which requires time sequence with high spatial resolution. Aims: .Our objective is to follow the properties of the magnetic concentrations during their life, in intensity (continuum and line core), magnetic field and Doppler velocity. Methods: .We have observed solar region NOAA

Th. Roudier; J. M. Malherbe; J. Moity; S. Rondi; P. Mein; Ch. Coutard

2006-01-01

185

An Extraordinary Magnetic Field Map of Mars  

NASA Astrophysics Data System (ADS)

A new global map of the magnetic field of Mars, with an order of magnitude improved sensitivity to crustal magnetization, is derived from Mars Global Surveyor mapping orbit magnetic field data. With this comes greatly improved spatial resolution and geologic intrpretation.

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

2004-03-01

186

The use of high magnetic fields at the study of magnetism and superconductivity in intermetallic compounds  

SciTech Connect

Magnetic fields have a large impact on the magnetic and superconducting properties of solids. High magnetic fields are required to reach magnetic saturation along a hard magnetic direction in a variety of rare-earth intermetallics, to break the ferrimagnetic moment configuration in specific 3d-4f intermetallics, to quench the strongly correlated electron states in heavy fermion compounds, to reach the upper critical fields in several classes of superconductors, to study flux-pinning phenomena in the high-{Tc} superconductors, etc. In the present review, the attention is focused to the field interval 20--50 tesla. Experiments in this field range are the privilege of specialized high magnetic field laboratories. There is a lively activity in this area of research with the number of participating institutes continuously growing.

Franse, J.J.M.; Boer, F.R. de; Frings, P.H.; Visser, A. de [Univ. of Amsterdam (Netherlands). Van der Waals-Zeeman Lab.

1994-03-01

187

Rotating magnetic beacons magnetic field strength size in SAGD  

Microsoft Academic Search

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted\\u000a gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of\\u000a 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The

Bing Tu; Desheng Li; Enhuai Lin; Bin Luo; Jian He; Lezhi Ye; Jiliang Liu; Yuezhong Wang

2010-01-01

188

Mystery of the magnetic field of Mars  

NASA Astrophysics Data System (ADS)

Research of interaction of the solar wind with bodies of Solar System is one of methods, which allows us to make the conclusion about substance of the bodies and about its magnetization. The investigation of the solar wind interaction with Mars and Phobos has been carried out using the data of the Soviet expedition "Phobos - 2" and the kinetic approach to study the data. It is shown, that the size of the Martian obstacle to the solar wind is actually the size of Mars, as a physical body. The weak ionosphere and crystal magnetic anomalies at Mars result in inelastic dispersion of particles of the solar wind on the Martian obstacle, which give additional accumulation of the plasma and magnetic field in front of the Martian obstacle. The more the density of the solar wind, the more will the pileup of the plasma in front of Mars. Mars has not magnetospheres, neither own, nor induced to give the additional size for the obstacle like the Earth. The tail inherent in the interaction of magnetized bodies with the solar wind plasma, practically, is absent at Mars. The magnetic topology of the Martian wake is a result of the flow by the warm plasma of the solar wind around Mars. The Phobos interaction with the solar wind has been investigated. Dependence of the pileup of the solar wind plasma ahead of Phobos from the ion skin-depth has been found, which shows the existence of an effective obstacle of Phobos with the sizes about 150-170 km. Source with equivalent magnetic moment as order 1015A m2 in Phobos leads to the development of such obstacle for the solar wind flow around Phobos. Thus the received results: absence of the intrinsic global magnetic field of Mars, the magnetization of the Martian moon of Phobos and so the crystal magnetic anomalies revealed by the MGS satellite on surface of Mars give the primal magnetic mystery of Mars. If we will understand it we may probably approach to the problem of lifelessness of Mars. It is necessary to remind that evidence of biological origin has been revealed in the Martian meteorite ALH84001 with chains of magnetite crystals.

Mordovskaya, V.

189

Unique topological characterization of braided magnetic fields  

NASA Astrophysics Data System (ADS)

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.; Hornig, G.

2013-01-01

190

Boston University Physics Applets: Magnetic Field Demonstration  

NSDL National Science Digital Library

This web page is an interactive physics simulation that explores magnetic fields. The user can add currents coming into or out of a simulated grid, and see the fields created. There is also a selection of pre-created fields, including bar magnets, loops, opposing magnets, and coils in uniform fields. Double-clicking on any point displays the full loop created by the magnetic field. This item is part of a larger collection of introductory physics simulations developed by the author. This is part of a collection of similar simulation-based student activities.

Duffy, Andrew

2008-08-23

191

Low-field magnetic resonance imaging of gases  

SciTech Connect

This is the final report of a six-month, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The main goal of this project was to develop the capability to conduct low-field magnetic resonance imaging of hyper-polarized noble gas nuclei and of thermally polarized protons in water. The authors constructed a versatile low-field NMR system using a SQUID gradiometer detector inside a magnetically shielded room. This device has sufficient low-field sensitivity to detect the small signals associated with NMR at low magnetic fields.

Schmidt, D.M.; Espy, M.A.

1998-11-01

192

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.

Lubell, Martin S. (Oak Ridge, TN)

1994-01-01

193

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

194

Near-Field Magnetic Dipole Moment Analysis.  

National Technical Information Service (NTIS)

This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective...

P. K. Harris

2003-01-01

195

Constant Current Source for Stable Magnetic Fields.  

National Technical Information Service (NTIS)

An electronic control system for stabilization of currents in magnetic fields is described. Three superimposed control stages with different characteristics provide optimum elimination of all interfering factors. The use of electrostatic and magnetic shie...

K. Weyand

1976-01-01

196

RESEARCH PAPERS : The complex-image method for calculating the magnetic and electric fields produced at the surface of the Earth by the auroral electrojet  

Microsoft Academic Search

For studying the auroral electrojet and for examining the effects it can produce in power systems on the ground, it is useful to be able to calculate the magnetic and electric fields that the electrojet produces at the surface of the Earth. Including the effects of currents induced in the Earth leads to a set of integral expressions, the numerical

D. H. Boteler; R. J. Pirjola

1998-01-01

197

THE EARTH'S YOUNG MAGNETIC FIELD  

Microsoft Academic Search

Invisible lines of magnetic force enclose our planet in what scientists call adipolarmagneticfield. Today these lines go from magnetic south to magnetic north, which are offset a few degrees from the geographic poles. Some minerals, like magnetite, can \\

Trevor Major

198

Field Research on Glacial Change  

NSDL National Science Digital Library

This video describes how field research -- in this case, making water measurements in rugged mountain locations -- helps us to understand the complex relationships among changing climate, populations, and water usage.

Thinktv; Domain, Teachers'

199

Alternating-Field Susceptometry and Magnetic Susceptibility of Supercondoctors. Presented at Office of Naval Research Workshop on Magnetic Susceptibility of Supercondoctors and Other Spin Systems. Held in Berkeley Spring, West Virginia on 20 May 1991.  

National Technical Information Service (NTIS)

The review critically analyzes current practice in the design, calibration, sensitivity determination, and operation of alternating-field susceptometers, and examines applications in magnetic susceptibility measurements of superconductors. Critical parame...

R. B. Goldfarb M. Lelental C. A. Thopmson

1991-01-01

200

Arc Discharges in a Curved Magnetic Field.  

National Technical Information Service (NTIS)

An experiment on arc discharges in hydrogen in a curved magnetic field is described. For a few milliseconds the discharge current flowed between two electrodes along the field lines of a toroidal magnetic field over an angle of 258 deg. The plasma was not...

F. C. Schueller

1974-01-01

201

Is the intergalactic magnetic field primordial?  

Microsoft Academic Search

We consider the various methods used to constrain the possible field strength of the present day intergalactic field and findB0(G)-10 as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies.

Martin Beech

1985-01-01

202

Intergalactic magnetic field and galactic WARPS  

Microsoft Academic Search

An alternative explanation of galactic warps is proposed, in which the intergalactic magnetic field (IGMF) is responsible for these structures. The model predicts that, to be efficient, the magnetic field must have a direction not much different from 45 deg with the galactic plane. The required values of the field strength are uncertain, of about 10 nG, higher values being

E. Battaner; E. Florido; M. L. Sanchez-Saavedra

1990-01-01

203

Fiber Bragg Grating Magnetic Field Sensor  

Microsoft Academic Search

In this paper we demonstrate experimentally a magnetic field sensor using a fiber Bragg grating. The shift in the Bragg condition as a result of strain applied on the fiber mounted on a nickel base by the magnetic field gives an indirect measure of the field. The proposed method overcomes the need for long fiber lengths required in methods such

K. V. Madhav; K. Ravi Kumar; T. Srinivas; S. Asokan

2006-01-01

204

Is the intergalactic magnetic field primordial?  

NASA Astrophysics Data System (ADS)

The various methods used to constrain the possible field strength of the present day intergalactic field are considered, and Bzero (G) less than 10 to the -10th is found as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies.

Beech, M.

1985-11-01

205

Extraterrestrial Magnetic Fields: Achievements and Opportunities  

Microsoft Academic Search

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

EDWARD J. SMITHAND; Charles Sonett

1976-01-01

206

Modeling solar force-free magnetic fields  

Microsoft Academic Search

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

B. C. Low; Y. Q. Lou

1990-01-01

207

The high field superconducting magnet program at LLNL: Annual report  

SciTech Connect

In FY 86 the program continued along several interrelated thrust areas. These thrust areas have been broadly labeled as follows: (1) Superconductor Research and Technology; (2) Magnet Systems Materials Technology; (3) Magnet Systems Design Technology; (4) High Field Test Facility; and (5) Technology Transfer.

Miller, J.R.; Chaplin, M.R.; Kerns, J.A.; Leber, R.L.; Rosdahl, A.R.; Slack, D.S.; Summers, L.T.; Zbasnik, J.P.

1986-12-01

208

Induced Magnetic Anisotropy of Ferrofluid Frozen in Magnetic Fields  

Microsoft Academic Search

The magnetization process of a ferrofluid whose carrier fluid is paraffin was investigated in the temperature range from 77 K to 300 K, as a function of the cooling field intensity and freezing rate. Phase transitions between the liquid and solid states can be simulated by using the ferrofluids as a magnetic probe. A uniaxial magnetic anisotropy was induced by

N. Inaba; H. Miyajima; S. Taketomi; S. Chikazumi

1989-01-01

209

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

210

Quark matter in a strong magnetic field  

SciTech Connect

The effect of a strong magnetic field on the stability and gross properties of bulk as well as quasibulk quark matter is investigated using the conventional MIT bag model. Both the Landau diamagnetism and the paramagnetism of quark matter are studied. How the quark hadron phase transition is affected by the presence of a strong magnetic field is also investigated. The equation of state of strange quark matter changes significantly in a strong magnetic field. It is also shown that the thermal nucleation of quark bubbles in a compact metastable state of neutron matter is completely forbidden in the presence of a strong magnetic field. {copyright} {ital 1996 The American Physical Society.}

Chakrabarty, S. [Department of Physics, University of Kalyani, District: Nadia, West Bengal 741 235 (India)]|[Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007 (India)

1996-07-01

211

Two dimensional frustrated magnets in high magnetic field  

NASA Astrophysics Data System (ADS)

Frustrated magnets in high magnetic field have a long history of offering beautiful surprises to the patient investigator. Here we present the results of extensive classical Monte Carlo simulations of a variety of models of two dimensional magnets in magnetic field, together with complementary spin wave analysis. Striking results include (i) a massively enhanced magnetocaloric effect in antiferromagnets bordering on ferromagnetic order, (ii) a route to an m = 1/3 magnetization plateau on a square lattice, and (iii) a cascade of phase transitions in a simple model of AgNiO2.

Seabra, L.; Shannon, N.; Sindzingre, P.; Momoi, T.; Schmidt, B.; Thalmeier, P.

2009-01-01

212

The Magnetic Fields of the Quiet Sun  

NASA Astrophysics Data System (ADS)

This work reviews our understanding of the magnetic fields observed in the quiet Sun. The subject has undergone a major change during the last decade (quiet revolution), and it will remain changing since the techniques of diagnostic employed so far are known to be severely biased. Keeping these caveats in mind, our work covers the main observational properties of the quiet Sun magnetic fields: magnetic field strengths, unsigned magnetic flux densities, magnetic field inclinations, as well as the temporal evolution on short time-scales (loop emergence), and long time-scales (solar cycle). We also summarize the main theoretical ideas put forward to explain the origin of the quiet Sun magnetism. A final prospective section points out various areas of solar physics where the quiet Sun magnetism may have an important physical role to play (chromospheric and coronal structure, solar wind acceleration, and solar elemental abundances).

Sánchez Almeida, J.; Martínez González, M.

2011-04-01

213

Status report of current biological, medical, and engineering research and significant study results regarding potential human health effects associated with power-frequency electric and magnetic fields. Report for May 1989-August 1990  

SciTech Connect

The report reviews planned and ongoing research on biological and health effects of 50- and 60-Hz electric and magnetic fields. The purpose of the report was to review results from research since May 1989 to determine new significant findings regarding potential human health impacts from electric-power frequency fields at levels expected from transmission and distribution sources. Information in the report came from a variety of sources (scientific meetings, sponsors of directed site visits and project reviews, International Data Base of ongoing and planned research on electric and magnetic fields) and may not appear in the scientific literature for several years. Information is presented on 120 ongoing and planned research projects throughout the world, of which many are focused in 4 major areas: cancer, reproduction and development, neuroendocrine system and mechanisms of interaction at the cellular and subcellular levels. There are 25 ongoing epidemiology studies, of which 21 are concerned with cancer and 4 with reproduction and development. Results from ongoing epidemiology studies dealing with cancer in which data are available support the results of many of the earlier studies in which there is an association between exposure to electric and magnetic fields and the incidence of cancer, particularly of the hematopoetic system and nervous system.

Not Available

1990-09-01

214

PRINCIPLE OF CORRECTION OF ASYMMETRIC MAGNETIC FIELDS IN BENDING MAGNETS  

Microsoft Academic Search

The generation of a high quality electron beam by a race- track microtron (RTM) requires highly precise magnetic fields in the two reversing magnets. At the RTM cascade MAMI (Mainz Microtron), a precision of 10 ?4 for the ver- tical field component By was achieved by symmetrical sur- face coils placed at the upper and lower pole surface in each

F. Hagenbuck; P. Jennewein; K.-H. Kaiser; H.-J. Kreidel; U. Ludwig-Mertin; M. Seidl

2002-01-01

215

Monitoring the Earth's Dynamic Magnetic Field  

USGS Publications Warehouse

The mission of the U.S. Geological Survey's Geomagnetism Program is to monitor the Earth's magnetic field. Using ground-based observatories, the Program provides continuous records of magnetic field variations covering long timescales; disseminates magnetic data to various governmental, academic, and private institutions; and conducts research into the nature of geomagnetic variations for purposes of scientific understanding and hazard mitigation. The program is an integral part of the U.S. Government's National Space Weather Program (NSWP), which also includes programs in the National Aeronautics and Space Administration (NASA), the Department of Defense (DOD), the National Oceanic and Atmospheric Administration (NOAA), and the National Science Foundation (NSF). The NSWP works to provide timely, accurate, and reliable space weather warnings, observations, specifications, and forecasts, and its work is important for the U.S. economy and national security. Please visit the National Geomagnetism Program?s website, http://geomag.usgs.gov, where you can learn more about the Program and the science of geomagnetism. You can find additional related information at the Intermagnet website, http://www.intermagnet.org.

Love, Jeffrey J.; Applegate, David; Townshend, John B.

2008-01-01

216

Magnetic-field effects in non-magnetic glasses  

NASA Astrophysics Data System (ADS)

Recently, it was found that the multi-component glass a-BaO-Al2O3-SiO2 exhibits unusual magnetic properties at very low temperatures. Thus the question arises whether this is a specialty of that particular glass or a more general phenomenon. We report here on our studies of the magnetic-field dependence of the dielectric properties of the borosilicate glass BK7 which contains only a negligible amount of magnetic impurities. Since this glass also responds sensitively to magnetic fields, our investigations demonstrate that the reaction of glasses to magnetic fields is not caused by magnetic impurities but reflects a more general phenomenon. In addition, we have observed that the variation of the dielectric constant and the loss angle with magnetic field depend on the amplitude of the electric field that is used to measure the glass capacitance. We present the data and discuss possible origins of the magnetic-field phenomena in non-magnetic glasses.

Wohlfahrt, M.; Strehlow, P.; Enss, C.; Hunklinger, S.

2001-12-01

217

Magnetohydrodynamics of the Earth'S Magnetic Field.  

National Technical Information Service (NTIS)

A survey of observational and theoretical work pertaining to the origin of planetary magnetic fields is given with special emphasis on the dynamo theory which attempts to explain these fields as arising from magnetohydrodynamic regenerative action. Some p...

G. Venezian

1967-01-01

218

Cosmic Rays in the Earth'S Magnetic Field.  

National Technical Information Service (NTIS)

Studies are presented of the behavior of cosmic rays in the earth's magnetic field. It discusses the theory of motion of charged particles in an idealized field model and presents results of trajectory calculations of asymptotic directions and cutoff rigi...

L. I. Dorman V. S. Smirnov M. I. Tyasto

1973-01-01

219

Measuring the off axis magnetic field within a Helmholtz Coil  

NASA Astrophysics Data System (ADS)

Helmholtz coils are used because they produce nearly uniform magnetic fields on-axis. Prior research, namely Graf's thin coil experiment [The Physics Teacher, pp. 360 (2012)], has accurately measured the axial magnetic field produced by a thin coil; however, the magnetic field off-axis is known to be significantly more complicated and cannot be calculated analytically. In this research, I have numerically determined the magnetic field off-axis in the region between the two coils and compared those calculations with measured values. I then determined the effect the deviation from uniformity has on the behavior of a charged particle moving through this region, such as in the well-known electron charge-to-mass ratio experiment.

Pluhar, Edward; Martell, Eric

2013-03-01

220

Analyzing and Modeling the Magnetic Field of Mars  

NASA Astrophysics Data System (ADS)

Presently Mars possesses no intrinsic magnetic field; rather its crust exhibits strong remanent magnetization primarily in the Southern Highlands. The deficiency of magnetization surrounding volcanic provinces and impact basins on Mars is attributed to evidence suggesting that the crust gained its magnetic remanence early on via an internal dynamo. This dynamo is believed to have become extinct by the time of the last major impacts. Measurements taken by Mars Global Surveyor (MGS) have been used to create a new map of Mars' crustal magnetic field. We present an analysis of these data in conjunction with topographical data taken from the Mars Orbiter Laser Altimeter (MOLA) to determine if magnetization in Mars' southern regions correlates with surface features displayed on topographic maps. MGS and MOLA data were used to identify and study a region of intense magnetic field beneath a 1500 km section of an impact basin in the western hemisphere of the Southern Highlands. In conjunction with the development of models and intensity plots for the radial component of this field, analysis of the possible shape, configuration and composition of the magnetic material beneath the crater was performed. Our models showed that the magnetic signature beneath the impact basin was produced by two adjacent blocks of magnetic material within the Martian crust. We found that the blocks were most likely rectangular in shape and were relatively closely spaced. They also possessed properties similar to those of stainless steel permanent magnets with magnetization directions of -90 degrees, and -45 degrees, respectively. The results of this research will contribute to future studies of Mars, specifically of its present magnetic state, magnetic history, and impact record. This research was made possible via funding from the North Carolina Space Grant Consortium.

Quick, L. C.; Acuna, M. H.; Connerney, J. E. P.

2005-12-01

221

Magnetic Field Investigations During ROSETTA's Steins Flyby  

NASA Astrophysics Data System (ADS)

During the recent Steins flyby of the ROSETTA spacecraft magnetic field measurements have been made with both, the RPC orbiter magnetometer and the ROMAP lander magnetometer. These combined magnetic field measurements allow a detailed examination of any magnetic signatures caused either directly by the asteroid or indirectly by Steins different modes of interaction with the solar wind. Comparing our measurements with simulation results show that Steins does not possess a significant remanent magnetization. The magnetization is estimated at less than 1 mAm2/kg. This is significantly different from results at Braille and Gaspra.

Glassmeier, K.; Auster, H.; Richter, I.; Motschmann, U.; RPC/ROMAP Teams

2009-05-01

222

Modeling Magnetic Field Topology at Jupiter with the Khurana Magnetic Field Model  

NASA Astrophysics Data System (ADS)

To explore the degree of coupling between the interplanetary magnetic field (IMF) and Jupiter's magnetosphere, we traced magnetic field lines from the polar region of the planet using the Khurana [1997, 2005] magnetic field model. We used a parameterized definition of the Jovian magnetopause created by Joy et al. [2002] that varies with the value of the solar wind dynamic pressure. We searched for field lines that cross the magnetopause and that potentially connect to the interplanetary magnetic field. We further explored the variation on magnetic field structure with local time orientation of Jupiter's dipole (i.e. Central Meridian Longitude) as well as upstream solar wind and IMF conditions.

Cohen, I.; Bagenal, F.

2008-12-01

223

Constrained superfields and supersymmetric magnetic field systems  

SciTech Connect

After Lancaster the authors examine chiral constraints in N = 2 superspace formulation for supersymmetric magnetic field systems. Such odd constraints are connected with the so-called spin-orbit coupling procedure of supersymmetrization. They propose new even constraints for magnetic supersymmetric systems and relate them to the standard procedure enhanced by Witten. These models describing spin-one half particles moving in a plane with a transverse magnetic field are compared and discussed. The cases of a constant magnetic field and of the harmonic oscillator are connected through different correspondences.

Dehin, D.; Hussin, V. (Universite de Liege, Physique Theorique et Mathematique, Institut de Physique au Sart Tilman, Batiment B.5, B-4000 Liege (BE))

1988-01-01

224

Ionospheric electric fields, currents, and resulting magnetic fields variations  

NASA Astrophysics Data System (ADS)

This thesis uses an equivalent circuit model to calculate ionospheric electric fields, current densities and introduced magnetic fields variations on the ground. The role of the field aligned current is examined. Using different wind models, we studied the electric field variations with altitude, season and solar activity. The ionospheric eastward electric field changes very little within the whole ionosphere. The southward (equatorward) electric field is large and changes quickly with height in the E region although it is nearly constant in the F region. The prereversal enhancement of the eastward electric field is produced by the F region dynamo. We conclude that the Forbes and Gillette tidal wind can reproduce most features of the Jicamarca experiment and the AE-E and DE-2 satellite observations of the electric fields. The HWM90 empirical wind model failed to produce the observed electric field and it seems the semidiurnal wind in HWM90 is too strong. The field aligned current is located mainly in the E and low F region. The non-coincidence of the geomagnetic and geographic equators has a strong effect on the field aligned current in the equatorial zone. The field aligned currents driven by Forbes' winds for March equinox and December solstice flow mainly from the southern to northern hemisphere in the morning and vice versa in the afternoon at F region heights. The observed magnetic field variations on the ground are well reproduced in our simulations. The field aligned current is the main contributor to the eastward magnetic field component in the equatorial zone. The longitudinal inequality of the northward magnetic field is introduced mainly by the variations of the local magnetic field intensity. The electric field variations have only a minor effect. The northward magnetic field variations with the solar activity are introduced by changes of the E region equatorward electric field and the Hall conductivity.

Du, Junhu

225

Magnetic field associated with active electrochemical corrosion  

Microsoft Academic Search

The purpose of this work is to provide a better understanding of the underlying sources of the magnetic field associated with ongoing electrochemical corrosion, to investigate the spatio-temporal information content of the corrosion magnetic field, and to evaluate its potential utility in non-invasive quantification of hidden corrosion. The importance of this work lies in the fact that conventional electrochemical instruments

Afshin Abedi

2000-01-01

226

Coronal Heating and the Photospheric Magnetic Field  

Microsoft Academic Search

Since magnetic field typically plays a role (either active or passive) in coronal heating theories, it may be possible to evaluate these theories by investigating the relationship between the coronal energy budget (the total power requirement of the corona) and measurable properties of the photospheric magnetic field. The X-ray flux is a useful proxy for the total power required to

C. E. Parnell; P. A. Sturrock

1997-01-01

227

Variability and topology of solar magnetic field  

Microsoft Academic Search

Observations of the large scale magnetic field in the photosphere taken at the Wilcox Solar Observatory since 1976 up to 2005 have been analyzed to deduce its latitudinal and longitudinal structures, its differential rotation, and their variability in time. The main results are the following: - The latitudinal structure of the solar magnetic field with a period of polarity change

E. A. Gavryuseva

2006-01-01

228

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

229

Coulomb crystals in the magnetic field  

NASA Astrophysics Data System (ADS)

The body-centered-cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic-field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields B?1014G ). The effect of the magnetic field on ion displacements in a strongly magnetized neutron star crust can suppress the nuclear reaction rates and make them extremely sensitive to the magnetic-field direction.

Baiko, D. A.

2009-10-01

230

Magnetic field decay in model SSC dipoles  

Microsoft Academic Search

The authors 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

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

1989-01-01

231

Magnetic fields and the solar corona  

Microsoft Academic Search

Coronal magnetic fields calculated by the methods developed in Paper I (Altschuler and Newkirk, 1969) and the empirical description of the solar corona of November 1966 derived in Paper II (Newkirket al., 1970) are combined in order to investigate what connection exists between the magnetic fields and the density structure of the corona.

Gordon Newkirk; Martin D. Altschuler

1970-01-01

232

Pure phase encode magnetic field gradient monitor  

Microsoft Academic Search

Numerous methods have been developed to measure MRI gradient waveforms and k-space trajectories. The most promising new strategy appears to be magnetic field monitoring with RF microprobes. Multiple RF microprobes may record the magnetic field evolution associated with a wide variety of imaging pulse sequences. The method involves exciting one or more test samples and measuring the time evolution of

Hui Han; Rodney P. MacGregor; Bruce J. Balcom

2009-01-01

233

Efficient Characterization of Magnetic Field Sources  

Microsoft Academic Search

A technique for the estimation of the magnetic field intensity emitted by industrial installations is presented. The method is best-suited for investigation of environmental magnetic field for health purposes. Simulation and measurement case-studies supporting the provided theoretical results are discussed

M. Bertocco; F. Dughiero; C. Greggio; E. Sieni; A. Sona

2006-01-01

234

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

235

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

236

Magnetic Fields, Ball Lightning and Campanology  

Microsoft Academic Search

WOODING suggests1 that ball lightning is a plasma vortex ring structure produced by a process similar to the ablation of a solid surface by a high power laser pulse. A plasma vortex ring structure requires a magnetic field; here I present two pieces of evidence to show that a magnetic field is associated with ball lightning, and which may help

A. J. F. Blair

1973-01-01

237

Magnetic field propagation in a stellar dynamo  

Microsoft Academic Search

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from

Gary A. Glatzmaier

1985-01-01

238

Space Quantization in a Gyrating Magnetic Field  

Microsoft Academic Search

The nonadiabatic transitions which a system with angular momentum J makes in a magnetic field which is rotating about an axis inclined with respect to the field are calculated. It is shown that the effects depend on the sign of the magnetic moment of the system. We therefore have an absolute method for measuring the sign and magnitude of the

I. I. Rabi

1937-01-01

239

Hydrogen atom moving across a magnetic field  

SciTech Connect

A hydrogen atom moving across a magnetic field is considered in a wide region of magnitudes of magnetic field and atom momentum. We solve the Schroedinger equation of the system numerically using an imaginary time method and find wave functions of the lowest states of atom. We calculate the energy and the mean electron-nucleus separation as a function of atom momentum and magnetic field. All the results obtained could be summarized as a phase diagram on the 'atom-momentum - magnetic-field' plane. There are transformations of wave-function structure at critical values of atom momentum and magnetic field that result in a specific behavior of dependencies of energy and mean interparticle separation on the atom momentum P. We discuss a transition from the Zeeman regime to the high magnetic field regime. A qualitative analysis of the complicated behavior of wave functions vs P based on the effective potential examination is given. We analyze a sharp transition at the critical momentum from a Coulomb-type state polarized due to atom motion to a strongly decentered (Landau-type) state at low magnetic fields. A crossover occurring at intermediate magnetic fields is also studied.

Lozovik, Yu.E.; Volkov, S.Yu. [Institute of Spectroscopy, Troitsk, Moscow region, 142190 (Russian Federation)

2004-08-01

240

Evaporation rate of water as a function of a magnetic field and field gradient.  

PubMed

The effect of magnetic fields on water is still a highly controversial topic despite the vast amount of research devoted to this topic in past decades. Enhanced water evaporation in a magnetic field, however, is less disputed. The underlying mechanism for this phenomenon has been investigated in previous studies. In this paper, we present an investigation of the evaporation of water in a large gradient magnetic field. The evaporation of pure water at simulated gravity positions (0 gravity level (ab. g), 1 g, 1.56 g and 1.96 g) in a superconducting magnet was compared with that in the absence of the magnetic field. The results showed that the evaporation of water was indeed faster in the magnetic field than in the absence of the magnetic field. Furthermore, the amount of water evaporation differed depending on the position of the sample within the magnetic field. In particular, the evaporation at 0 g was clearly faster than that at other positions. The results are discussed from the point of view of the evaporation surface area of the water/air interface and the convection induced by the magnetization force due to the difference in the magnetic susceptibility of water vapor and the surrounding air. PMID:23443127

Guo, Yun-Zhu; Yin, Da-Chuan; Cao, Hui-Ling; Shi, Jian-Yu; Zhang, Chen-Yan; Liu, Yong-Ming; Huang, Huan-Huan; Liu, Yue; Wang, Yan; Guo, Wei-Hong; Qian, Ai-Rong; Shang, Peng

2012-12-11

241

Magnetic isotope and magnetic field effects on the DNA synthesis.  

PubMed

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc). PMID:23851636

Buchachenko, Anatoly L; Orlov, Alexei P; Kuznetsov, Dmitry A; Breslavskaya, Natalia N

2013-07-13

242

Magnetic isotope and magnetic field effects on the DNA synthesis  

PubMed Central

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions 24Mg2+, 25Mg2+ and 26Mg2+ in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying 24Mg2+ and 26Mg2+ ions with spinless, non-magnetic nuclei 24Mg and 26Mg. However, 25Mg2+ ions with magnetic nucleus 25Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with 24Mg2+ and 26Mg2+ ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn2+ ions carrying magnetic 67Zn and non-magnetic 64Zn nuclei, respectively. A new, ion–radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion–radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

Buchachenko, Anatoly L.; Orlov, Alexei P.; Kuznetsov, Dmitry A.; Breslavskaya, Natalia N.

2013-01-01

243

Vehicle detection using a magnetic field sensor  

Microsoft Academic Search

The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m2(Ampere-meters2), while for a school bus it is about 2000 A-m2. When the vehicle is modeled as an ideal

S. V. Marshall

1978-01-01

244

Intergalactic Magnetic Fields from Quasar Outflows  

Microsoft Academic Search

Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of\\u000a a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and\\u000a calculate their distribution as a function magnetic field strength at different redshifts. We find that by a redshift \\u000a z ~ <\\/font\\u000a>3z \\\\sim

Steven Furlanetto; Abraham Loeb

2002-01-01

245

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

246

High Field Magnets With HTS Conductors  

Microsoft Academic Search

Development of high-field magnets using high temperature superconductors (HTS) is a core activity at the NHMFL. Magnet technology based on both YBCO-coated tape conductors and Bi-2212 round wires is being pursued. Two specific projects are underway. The first is a user magnet with a 17 T YBCO coil set which, inside an LTS outsert, will generate a combined field of

H. W. Weijers; U. P. Trociewitz; W. D. Markiewicz; J. Jiang; D. Myers; E. E. Hellstrom; A. Xu; J. Jaroszynski; P. Noyes; Y. Viouchkov; D. C. Larbalestier

2010-01-01

247

Magnetic Instabilities in High Field Superconductors  

Microsoft Academic Search

In the process of magnetizing cylindrical specimens of a typical high field superconductor Nb-50 at.%Ti, flux jumps were induced by magnetic disturbances. The stability limit field Hfj increased steadily with increasing temperature, and no magnetic instability occurred for temperatures in excess of about 6.5 K. The calculation of Hfj was performed taking into account the cylindrical sample geometry and the

Tatsuo Akachi; Takeshi Ogasawara; Ko Yasukochi

1981-01-01

248

Orienting Paramecium with intense static magnetic fields  

NASA Astrophysics Data System (ADS)

Recent experiments on cell division suggest the application of intense static magnetic fields as a novel tool for the manipulation of biological systems [1]. The magnetic field appears to couple to the intrinsic anisotropies in the diamagnetic components of the cells. Here, we present measurements of the intrinsic average diamagnetic anisotropy of the whole single celled ciliate, Paramecium Caudatum. Magnetic fields, 2.5 T < B < 8 T were applied to immobilized (non-swimming) Paramecium Caudatum that were suspended in a density matched medium. The organisms align with their long axis parallel to the applied magnetic field. Their intrinsic diamagnetic anisotropy is 3x10-11 in cgs units. We will discuss the implications of these results for employing magnetic fields to probe the behavior of swimming Paramecium. [1] J. M. Valles, Jr. et al., Expt. Cell Res.274, 112-118 (2002).

Valles, James M., Jr.; Guevorkian, Karine; Quindel, Carl

2004-03-01

249

Materials Processing in Magnetic Fields  

NASA Astrophysics Data System (ADS)

The latest in lattice QCD -- Quark-gluon plasma physics -- String theory and exact results in quantum field theory -- The status of local supersymmetry.Supersymmetry in nuclei -- Inflation, dark matter, dark energy -- How many dimensions are really compactified? -- Horizons -- Neutrino oscillations physics -- Fundamental constants and their possible time dependence.Highlights from BNL. new phenomena at RHIC -- Highlights from BABAR -- Diffraction studied with a hard scale at HERA -- The large hadron collider: a status report -- Status of non-LHC experiments at CERN -- Highlights from Gran Sass.Fast automatic systems for nuclear emulsion scanning: technique and experiments -- Probing the QGP with charm at ALICE-LHC -- magnetic screening length in hot QCD -- Non-supersymmetric deformation of the Klebanov-Strassler model and the related plane wave theory -- Holographic renormalization made simple: an example -- The kamLAND impact on neutrino oscillations -- Particle identification with the ALIC TOF detector at very high multiplicity -- Superpotentials of N = 1 SUSY gauge theories -- Measurement of the proton structure function F2 in QED compton scattering at HERA -- Yang-Mills effective action at high temperature -- The time of flight (TOF) system of the ALICE experiment -- Almost product manifolds as the low energy geometry of Dirichlet Brane.

Schneider-Muntau, Hans J.; Wada, Hitoshi

250

Warm inflation in presence of magnetic fields  

NASA Astrophysics Data System (ADS)

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 de 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's proper time method.

Piccinelli, Gabriella; Sánchez, Ángel; Ayala, Alejandro; Mizher, Ana Julia

2013-07-01

251

An overview of the 45-T hybrid magnet system for the new National High Magnetic Field Laboratory  

Microsoft Academic Search

The new National High Magnetic Field Laboratory (NHMFL) at Tallahassee, Florida is committed to putting into operation in 1995 a 45-T Hybrid Magnet System to support research in steady, high magnetic fields. This facility will be accessible by qualified users world-wide on the basis of proposal and review. The more prominent components of this system will be a 24-MW resistive

J. R. Miller; M. D. Bird; S. Bole; A. Bonito-Oliva; Y. Eyssa; W. J. Kenney; T. A. Painter; H.-J. Schneider-Muntau; L. T. Summers; S. W. van Sciver; S. Welton; R. J. Wood; J. E. C. Williams; S. Bobrov; Y. Iwasa; M. Leupold; V. Stejskal; R. Weggel

1994-01-01

252

Ohm's law for mean magnetic fields  

SciTech Connect

Spatially complicated magnetic fields are frequently treated as the sum of a large, slowly varying, mean field and a small, rapidly varying, field. The primary effect of the small field is to modify the Ohm's law of the mean field. A set of plausible assumptions leads to a form of the mean field Ohm's law which is fundamentally different from the conventional alpha effect of dynamo theory.

Boozer, A.H.

1984-11-01

253

Magnetic field-assisted electrochemical discharge machining  

NASA Astrophysics Data System (ADS)

Electrochemical discharge machining (ECDM) is an effective unconventional method for micromachining in non-conducting materials, such as glass, quartz and some ceramics. However, since the spark discharge performance becomes unpredictable as the machining depth increases, it is hard to achieve precision geometry and efficient machining rate in ECDM drilling. One of the main factors for this is the lack of sufficient electrolyte flow in the narrow gap between the tool and the workpiece. In this study a magnetohydrodynamic (MHD) convection, which enhances electrolyte circulation has been applied to the ECDM process in order to upgrade the machining accuracy and efficiency. During electrolysis in the presence of a magnetic field, the Lorenz force induces the charged ions to form a MHD convection. The MHD convection then forces the electrolyte into movement, thus enhancing circulation of electrolyte. Experimental results show that the MHD convection induced by the magnetic field can effectively enhance electrolyte circulation in the micro-hole, which contributes to higher machining efficiency. Micro-holes in glass with a depth of 450 µm are drilled in less than 20 s. At the same time, better electrolyte circulation can prevent deterioration of gas film quality with increasing machining depth, while ensuring stable electrochemical discharge. The improvement in the entrance diameter thus achieved was 23.8% while that in machining time reached 57.4%. The magnetic field-assisted approach proposed in the research does not require changes in the machining setup or electrolyte but has proved to achieve significant enhancement in both accuracy and efficiency of ECDM.

Cheng, Chih-Ping; Wu, Kun-Ling; Mai, Chao-Chuang; Hsu, Yu-Shan; Yan, Biing-Hwa

2010-07-01

254

Probing Primordial Magnetic Fields Using Ly? Clouds  

NASA Astrophysics Data System (ADS)

From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h -1 Mpc) as compared to the usual ?CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly? clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly? clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly? opacity for this case and compare our theoretical estimates of Ly? opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n ~= -3.

Pandey, Kanhaiya L.; Sethi, Shiv K.

2013-01-01

255

Mercury's internal magnetic field: Constraints on fields of crustal origin  

NASA Astrophysics Data System (ADS)

Observations of Mercury's internal magnetic field during MESSENGER's first flyby (M1) and the first and third flybys of Mariner 10 (M10-I, M10-III) suggest that small-scale crustal magnetic fields, if they exist, are at the limit of resolution. Small-scale crustal fields are most easily identified near closest approach (CA) as features with wavelengths comparable to, or larger than, the spacecraft altitude. One small feature (< 4 nT in magnitude) encountered near CA during MESSENGER's first flyby may be either a crustal magnetic field or a plasma pressure effect. By means of Parker's constrained optimization approach, with no assumptions on the direction of magnetization, we can place constraints on the product of magnetization and magnetized layer thickness from such observations. The second flyby (M2) will allow additional constraints to be placed on the presence of small-scale fields, and correlations will be possible among topographic profiles measured by the Mercury Laser Altimeter (MLA), features seen on MESSENGER and Mariner 10 images, and any variations in the internal field. This flyby will acquire the first images of the CA region of M10-III, which has been pivotal in establishing the dipolar character of Mercury's magnetic field. Our ability to isolate small-scale crustal magnetic fields has been hindered by the limited coverage to date, as well as the difficulty in isolating the internal field. Across the terrestrial planets and the Moon, minimum magnetization contrast and iron abundance in the crust show a positive correlation. This correlation suggests that crustal iron content plays a determining role in the strength of crustal magnetization.

Purucker, M. E.; Sabaka, T. J.; Solomon, S. C.; Anderson, B. J.; Korth, H.; Zuber, M. T.; Neumann, G. A.; Head, J. W.; Johnson, C. L.; Uno, H.

2008-12-01

256

The Protogalactic Origin for Cosmic Magnetic Fields  

Microsoft Academic Search

It is demonstrated that strong magnetic fields are produced from a zero\\u000ainitial magnetic field during the pregalactic era, when galaxies are first\\u000aforming. Their development proceeds in three phases. In the first phase, weak\\u000amagnetic fields are created by the Biermann battery mechanism, acting in\\u000ashocked parts of the intergalactic medium where caustics form and intersect. In\\u000athe second

Russell M. Kulsrud; Renyue Cen; Jeremiah P. Ostriker; Dongsu Ryu

1996-01-01

257

Turbulence and Magnetic Fields in Astrophysical Plasmas  

Microsoft Academic Search

Magnetic fields permeate the Universe. They are found in planets, stars, accretion discs, galaxies, clusters of galaxies,\\u000a and the intergalactic medium. While there is often a component of the field that is spatially coherent at the scale of the\\u000a astrophysical object, the field lines are tangled chaotically and there are magnetic fluctuations at scales that range over\\u000a orders of magnitude.

Alexander A. Schekochihin; Steven C Cowley

2007-01-01

258

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

259

Emittance measurement in a magnetic field  

SciTech Connect

Emittance can be measured by intercepting an electron beam on a range thick plate and then observing the expansion of beamlets transmitted through small holes. The hole size is selected to minimize space charge effects. In the presence of a magnetic field the beamlets have a spiral trajectory and the usual field free formulation must be modified. To interpret emittance in the presence of a magnetic field an envelope equation is derived in the appropriate rotating frame. 1 ref.

Boyd, J.K.

1991-04-15

260

Manipulating Cells with Static Magnetic Fields  

NASA Astrophysics Data System (ADS)

We review our investigations of the use of static magnetic fields, B, for manipulating cells and cellular processes. We describe how B fields modify the cell division pattern of frog embryos and consequently can be used to probe the pattern determinants. We also observe that magnetic fields modify the swimming behavior of Paramecium Caudatum. We describe these modifications and their potential application to investigations of their swimming behavior.

Valles, J. M.; Guevorkian, K.

2005-07-01

261

Magnetic field effects on dielectrophoresis in manganites  

NASA Astrophysics Data System (ADS)

Perovskite-type manganese oxides (manganites) are of interest for many of the different properties they possess, including colossal magnetoresistance (CMR) and ferroelectric behavior. With the application of an electric field, large resistance decreases have been noted near the insulator-to-metal transition temperature in samples of (La1-yPry)1-xCaxMnO3 (LPCMO). Two proposed models have emerged to explain the behavior, dielectric breakdown and dielectrophoresis, with experimental evidence showing some aspects of the dielectrophoresis model to be correct. However, neither model accounts for magnetic interactions among the ferromagnetic metallic regions and the effects of a magnetic field applied in conjunction with an electric field. We have performed measurements on LPCMO samples by varying the strength and orientation of the magnetic field and the applied voltage. Cross-shaped microstructures have been made on LPCMO samples to allow us to investigate the effects of sample size on dielectrophoresis. We will present resistance and magnetization data obtained on LPCMO samples at various magnetic field strengths, magnetic field orientations, and sample sizes to elucidate the effect of magnetic interactions on dielectrophoresis induced transport and magnetic properties.

Grant, Daniel; Dragiev, Galin; Biswas, Amlan

2013-03-01

262

Vector Magnetic Field in Emerging Flux Regions  

NASA Astrophysics Data System (ADS)

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

Schmieder, B.; Pariat, E.

263

Magnetic field considerations in fusion power plant environs  

Microsoft Academic Search

A summary of magnetic field production mechanisms and effects is given. Discussions are included on the following areas: (1) stray magnetic and electric fields from tokamaks, (2) methods for reducing magnetic fields, (3) economics of magnetic field reductions, (4) forces on magnetizable objects near magnetic confinement fusion reactors, (5) electric field transients in tokamaks, (6) attenuation and decay of electromagnetic

H. B. Liemohn; D. L. Lessor; B. H. Duane

1976-01-01

264

Magnetic Field Extrapolations And Current Sheets  

NASA Astrophysics Data System (ADS)

Solar flares and coronal mass ejections (CMEs) --- phenomena which impact our society, but are scientifically interesting in themselves --- are driven by free magnetic energy in the coronal magnetic field. Since the coronal magnetic field cannot be directly measured, modelers often extrapolate the coronal field from the photospheric magnetograms --- the only field measurements routinely available. The best extrapolation techniques assume that the field is force free (coronal currents parallel the magnetic field), but that currents are not simply a linear function of the magnetic field. Recent tests, however, suggest that such non-linear force-free field (NLFFF) extrapolation techniques often underestimate free magnetic energy. We hypothesize that, since relaxation-based NLFFF techniques tend to smooth field discontinuities, such approaches will fail when current sheets are present. Here, we test this hypothesis by applying the Optimization NLFFF method to two configurations from an MHD simulation --- one with strong current concentrations, and one with weak concentrations. This work is supported by a NASA Sun-Earth Connections Theory grant to UC-Berkeley.

Welsch, Brian; De Moortel, I.; McTiernan, J. M.

2007-05-01

265

Neutron Star Crust in Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

We discuss the effects of strong magnetic fields through Landau quantization of electrons on the structure and stability of nuclei in neutron star crust. In strong magnetic fields, this leads to the enhancement of the electron number density with respect to the zero field case. We obtain the sequence of equilibrium nuclei of the outer crust in the presence of strong magnetic fields adopting most recent versions of the experimental and theoretical nuclear mass tables. For B ~ 1016G, it is found that some new nuclei appear in the sequence and some nuclei disappear from the sequence compared with the zero field case. Further we investigate the stability of nuclei in the inner crust in the presence of strong magnetic fields using the Thomas-Fermi model. The coexistence of two phases of nuclear matter - liquid and gas, is considered in this case. The proton number density is significantly enhanced in strong magnetic fields B ~ 1017G through the charge neutrality. We find nuclei with larger mass number in the presence of strong magnetic fields than those of the zero field. These results might have important implications for the transport properties of the crust in magnetars.

Nandi, Rana; Bandyopadhyay, Debades

2011-09-01

266

Global magnetic fields: variation of solar minima  

NASA Astrophysics Data System (ADS)

The topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using H ? charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle. The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed. We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the large-scale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

Tlatov, Andrey G.; Obridko, Vladimir N.

2012-07-01

267

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

268

Polarization Diagnostics of Solar Magnetic Fields  

NASA Astrophysics Data System (ADS)

The solar atmosphere is a highly ionized medium which is the playground of magnetic fields. In the deepest layer (the photosphere), magnetic fields disturb the 'normal' fluid motions forcing the plasma to behave incounterintuitive ways; in the outer layers (the chromosphere and the corona) magnetic fields rule, making the plasma levitate or even ejecting it out of the gravitational well of the Sun, with important consequences for us here on Earth. However, magnetic fields are elusive. The only quantitative evidence of their presence is through the polarization state of the light emitted by the plasma they are playing with. Remote sensing of magnetic fields from 150 million km away through spectropolarimetry is a challenge on applied physics as well as an art. It requires the application of quantum mechanics, radiative transfer theory, and advanced optics to the interpretation and analysis of spectropolarimetric observations. I will review standard diagnostic techniques and recent developments on this field. I will discuss their limitations and how to overcome them through the complementary aspects of different diagnostic techniques, spectral regions, and statistical analysis. Finally, I will review what are the main areas for progress in this regard: most notably, the 'measurement' of magnetic fields in the extremely dilute and weakly magnetized outer layers of the sun.

Manso Sainz, R.

2011-12-01

269

New Magnetic phases of holmium in a magnetic field  

SciTech Connect

We have examined the behavior of two well-characterized single crystals ofholmium in a magnetic field applied along the /ital c/ axis in a temperaturerange from 90 to 140 K, using magnetization and dilatometric measurements. Wehave found several new phases in this previously unexplored region of the phasediagram.

Steinitz, M. O.; Kahrizi, M.; Tindall, D. A.; Ali, N.

1989-07-01

270

Relationship between the magnetic hyperfine field and the magnetic moment  

Microsoft Academic Search

Based on experimental data it is shown, for some chosen alloys and compounds of iron, that there is no unique relationship between the 57Fe-site magnetic hyperfine field, Bhf, and the magnetic moment per Fe atom, ?. Instead, the Bhf–? plot consists of several branches, each of them being characteristic of a given alloy or compound. Consequently, the effective proportionality constant

S. M. Dubiel

2009-01-01

271

The Earth's Magnetic Field Lines And Earthquake Relations  

NASA Astrophysics Data System (ADS)

Earthquake is one of the natural disasters and very important for human life. A lot of people die every year all over the world due to earthquakes. It is very difficult to develop early warning method for earthquakes because of it has 3000 parameters. The earthquake scientists and other people involved are very hard working about this matter. Governments allocate a significant budget for earthquakes. In this study, the earth magnetic field has been researched for early warning. The questions are any tectonic plate movement is effect of the Earth magnetic field lines or changing of the Earth magnetic field lines are effect any tectonic plate. Greater than 7 M earthquakes have been chosen in this study. And 12 years period changing graphics of the earth magnetic field lines where the chosen earthquake locals have been taken.

Urusan, Ahmet Yucel

2011-12-01

272

How are static magnetic fields detected biologically?  

NASA Astrophysics Data System (ADS)

There is overwhelming evidence that life, from bacteria to birds to bats, detects magnetic fields, using the fields for orientation or navigation. Indeed there are recent reports (based on Google Earth imagery) that cattle and deer align themselves with the earth's magnetic field. [1]. The development of frog and insect eggs are changed by high magnetic fields, probably through known physical mechanisms. However, the mechanisms for eukaryotic navigation and alignment are not clear. Persuasive published models will be discussed. Evidence, that static magnetic fields might produce therapeutic effects, will be updated [2]. [4pt] [1] S. Begall, et al., Proc Natl Acad Sci USA, 105:13451 (2008). [0pt] [2] L. Finegold and B.L. Flamm, BMJ, 332:4 (2006).

Finegold, Leonard

2009-03-01

273

XUV harmonic enhancement by magnetic fields  

SciTech Connect

We examine three ways to enhance harmonic output of an XUV planar free-electron laser (FEL) operating in the Compton regime. The first method is to increase the rms static magnetic field, making it as large as possible. The second is by adding effective magnetic fields at the harmonics, thereby increasing the coupling to the harmonics. The third is by phase programming; i.e. programming the magnetic field to introduce jumps in the phase of the electrons as they move through phase space.

Elliott, C.J.; Schmitt, M.J.

1986-09-01

274

Magnetic field dependent tunneling in glasses  

PubMed

We report on experiments giving evidence for quantum effects of electromagnetic flux in barium alumosilicate glass. In contrast to expectation, below 100 mK the dielectric response becomes sensitive to magnetic fields. The experimental findings include both lifting of the dielectric saturation by weak magnetic fields and oscillations of the dielectric response in the low temperature resonant regime. As the origin of these effects we suggest that the magnetic induction field violates the time reversal invariance leading to a flux periodicity in the energy levels of tunneling systems. At low temperatures, this effect is strongly enhanced by the interaction between tunneling systems and thus becomes measurable. PMID:11017665

Strehlow; Wohlfahrt; Jansen; Haueisen; Weiss; Enss; Hunklinger

2000-02-28

275

Magnetic field structures in chemically peculiar stars  

NASA Astrophysics Data System (ADS)

We report the results of magnetic field modelling of around 50 CP stars, performed using the "magnetic charges" technique. The modelling shows that the sample reveals four main types of magnetic configurations: 1) a central dipole, 2) a dipole, shifted along the axis, 3) a dipole, shifted across the axis, and 4) complex structures. The vast majority of stars has the field structure of a dipole, shifted from the center of the star. This shift can have any direction, both along and across the axis. A small percentage of stars possess field structures, formed by two or more dipoles.

Glagolevskij, Yu. V.

2011-04-01

276

Magnetic field quality analysis using ANSYS  

SciTech Connect

The design of superconducting magnets for particles accelerators requires a high quality of the magnetic field. This paper presents an ANSYS 4.4A Post 1 macro that computes the field quality performing a Fourier analysis of the magnetic field. The results show that the ANSYS solution converges toward the analytical solution and that the error on the multipole coefficients depends linearly on the square of the mesh size. This shows the good accuracy of ANSYS in computing the multipole coefficients. 2 refs., 16 figs., 4 tabs.

Dell'Orco, D.; Chen, Y.

1991-03-01

277

Magnetic Field Dependent Tunneling in Glasses  

NASA Astrophysics Data System (ADS)

We report on experiments giving evidence for quantum effects of electromagnetic flux in barium alumosilicate glass. In contrast to expectation, below 100 mK the dielectric response becomes sensitive to magnetic fields. The experimental findings include both lifting of the dielectric saturation by weak magnetic fields and oscillations of the dielectric response in the low temperature resonant regime. As the origin of these effects we suggest that the magnetic induction field violates the time reversal invariance leading to a flux periodicity in the energy levels of tunneling systems. At low temperatures, this effect is strongly enhanced by the interaction between tunneling systems and thus becomes measurable.

Strehlow, P.; Wohlfahrt, M.; Jansen, A. G. M.; Haueisen, R.; Weiss, G.; Enss, C.; Hunklinger, S.

2000-02-01

278

[Weak magnetic fields and cognitive activity].  

PubMed

The influence of natural level of uniform magnetic field (to 200 microT) on Wistar rat cognition was studied in this work. It was found that influence of disturbed Earth magnetic field has caused a long depression of explorative activity only in the presence of information loading. Such depression was removed only after short external stimulation. After this stimulation rats were able to learn by themselves and it took them twice less time than in the control (nootropic effect). It is suggested that a weak magnetic field disturbances may be considered as a negative psychogenic factor which distorts normal conditions for cognitive activity. PMID:8962888

Nikol'skaia, K A; Shtemler, A V; Savonenko, A V; Osipov, A I; Nikol'ski?, S V

279

Environmental magnetic fields: Influences on early embryogenesis  

SciTech Connect

A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. (Univ. of Texas Health Science Center, San Antonio (United States))

1993-04-01

280

Plasma Dynamics in Pulsed Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

We describe recent studies of the interaction of fast-rising magnetic fields with multi-species plasmas of densities 10^13-10^15 cm-3. The configurations studied are planar or coaxial gaps, prefilled with plasmas that are driven by 80-400 ns current pulses. The diagnostics is based on time-dependent spectroscopic observations that are spatially resolved in 3D using plasma-doping techniques. The measurements include the magnetic-field structure (from Zeeman splitting), ion velocity distributions (from Doppler profiles), electric fields (from line shapes of allowed and forbidden transitions), and non-Maxwellian electron energy distribution (from line ratios). It is found that the magnetic field propagates in the plasma faster than expected from diffusion. Also, the field spatial distribution is inconsistent with diffusion. The observed broad current channel, as well as non-dependence of the magnetic field evolution on the current polarity, cannot be explained by the available Hall-field theories. Moreover, detailed observations reveal that magnetic field penetration and plasma reflection occur simultaneously, leading to ion-species separation [1, 2], which are also not predicted by Hall-field theories. Measurements of the reflected-proton velocities (twice the magnetic field velocity) show that the protons dissipate a significant fraction of the magnetic field energy. A possible mechanism previously formulated for astrophysical plasmas, based on the formation of small-scale density fluctuations (perhaps as a result of the Rayleigh-Taylor instability) that lead to field penetration via the Hall mechanism, has recently been suggested. The new phenomena observed require novel theoretical treatments. Applications include plasmas under high currents and space physics. 1. A. Weingarten et al., Phys. Rev. Lett. 87, 115004 (2001). 2. R. Arad, et al., Phys. Plasmas 10, 112 (2003).

Maron, Yitzhak

2003-10-01

281

Random errors in the magnetic field coefficients of superconducting magnets  

SciTech Connect

Random errors in the multipole magnetic coefficients of superconducting magnet have been of continuing interest in accelerator research. The Superconducting Super Collider (SSC) with its small magnetic aperture only emphasizes this aspect of magnet design, construction, and measurement. With this in mind, we present a magnet model which mirrors the structure of a typical superconducting magnet. By taking advantage of the basic symmetries of a dipole magnet, we use this model to fit the measured multipole rms widths. The fit parameters allow us then to predict the values of the rms multipole errors expected for the SSC dipole reference design D, SSC-C5. With the aid of first-order perturbation theory, we then give an estimate of the effect of these random errors on the emittance growth of a proton beam stored in an SSC. 10 refs., 6 figs., 2 tabs.

Herrera, J.; Hogue, R.; Prodell, A.; Wanderer, P.; Willen, E.

1985-01-01

282

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

283

Directed Plasma Flow across Magnetic Field  

NASA Astrophysics Data System (ADS)

The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.

Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.

2008-04-01

284

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

285

Magnetic field evolution of accreting neutron stars  

NASA Astrophysics Data System (ADS)

We discuss the effect of accretion on the evolution of the magnetic field of a neutron star and highlight the main unresolved issues. Charged, accreted matter is funneled towards the magnetic poles where it heats the stellar surface and alters its magnetic structure resulting in an overall reduction of the magnetic dipole moment. Mechanisms for accretion-induced field reduction include accelerated Ohmic decay, vortex-fluxoid interactions, and magnetic burial or screening. We discuss how these can be integrated into a global model and detail recent self-consistent, three-dimensional, magneto-hydrodynamic, calculations (using analytic Grad-Shafranov methods and the numerical solver ZEUS-MP) which incorporate global resistive instabilities. These models can explain why neutron stars in binaries have systematically lower magnetic dipole moments than isolated neutron stars. Finally we discuss applications including the evolution of accreting millisecond pulsars and type-I X-ray bursts, magnetars, and gravitational waves.

Payne, D. J. B.; Vigelius, M.; Melatos, A.

2008-10-01

286

Reconnection Rates of Magnetic Fields.  

National Technical Information Service (NTIS)

The Sweet-Parker and Petschek scalings of magnetic reconnection rate are modified to include the effect of the viscosity. The modified scalings show that the viscous effect can be important in high- beta plasmas. The theoretical reconnection scalings are ...

W. Park D. A. Monticello R. B. White

1983-01-01

287

CHARACTERISTIC LENGTHS OF MAGNETIC FIELD IN MAGNETOHYDRODYNAMIC TURBULENCE  

SciTech Connect

In the framework of turbulence dynamo, flow motions amplify a weak seed magnetic field through the stretching of field lines. Although the amplification process has been a topic of active research, less attention has been paid to the length scales of magnetic field. In this Letter, we describe a numerical study on characteristic lengths of magnetic field in magnetohydrodynamic turbulence. We considered the case of very weak or zero mean magnetic field, which is applicable to the turbulence in the intergalactic space. Our findings are as follows. (1) At saturation, the peak of magnetic field spectrum occurs at approxL{sub 0}/2, where L{sub 0} is the energy injection scale, while the most energy containing scale is approxL{sub 0}/5. The peak scale of spectrum of projected, two-dimensional field is approxL{sub 0}. (2) During the stage of magnetic field amplification, the energy equipartition scale shows a power law increase of approxt {sup 1.5}, while the integral and curvature scales show a linear increase. The equipartition, integral, and curvature scales saturate at approxL{sub 0}, approx0.3L{sub 0}, and approx0.15L{sub 0}, respectively. (3) The coherence length of magnetic field defined in the Faraday rotation measure (RM) due to the intergalactic magnetic field (IGMF) is related to the integral scale. We present a formula that expresses the standard deviation of RM, sigma{sub RM}, in terms of the integral scale and rms strength of the IGMF, and estimate that sigma{sub RM} would be approx100 and approx a few rad m{sup -2} for clusters and filaments, respectively.

Cho, Jungyeon [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of); Ryu, Dongsu, E-mail: cho@canopus.cnu.ac.k, E-mail: ryu@canopus.cnu.ac.k

2009-11-01

288

Magnetic Instabilities in High Field Superconductors  

NASA Astrophysics Data System (ADS)

In the process of magnetizing cylindrical specimens of a typical high field superconductor Nb-50 at.%Ti, flux jumps were induced by magnetic disturbances. The stability limit field Hfj increased steadily with increasing temperature, and no magnetic instability occurred for temperatures in excess of about 6.5 K. The calculation of Hfj was performed taking into account the cylindrical sample geometry and the critical state equation JcB1-?{=}?. According to the relative magnitudes of the magnetic diffusivity Dm and the thermal diffusivity Dt, the expression of Hfj was derived for two cases; (1) Dm>Dt, and (2) Dm?Dt. Good agreement between experiment and theory was obtained on the stability limit field Hfj and the temperature above which magnetic instabilities do not take place.

Akachi, Tatsuo; Ogasawara, Takeshi; Yasuk?chi, K?

1981-08-01

289

Magnetic field gradient effects on Rayleigh-Taylor instability with continuous magnetic field and density profiles  

SciTech Connect

In this paper, the effects of magnetic field gradient (i.e., the magnetic field transition layer effects) on the Rayleigh-Taylor instability (RTI) with continuous magnetic field and density profiles are investigated analytically. The transition layers of magnetic field and density with two different typical profiles are studied and the analytic expressions of the linear growth rate of the RTI are obtained. It is found that the magnetic field effects strongly reduce the linear growth rate of the RTI, especially when the perturbation wavelength is short. The linear growth rate of the RTI increases with the thickness of the magnetic field transition layer, especially for the case of small thickness of the magnetic field transition layer. When the magnetic field transition layer width is long enough, the linear growth rate of the RTI can be saturated. Thus when one increases the width of the magnetic field transition layer, the linear growth rate of the RTI increases only in a certain range, which depends on the magnetic field strength. The numerical results are compared with the analytic linear growth rates and they agree well with each other.

Yang, B. L. [Graduate School, China Academy of Engineering Physics, Beijing 100088 (China); Wang, L. F.; Ye, W. H. [HEDPS and CAPT, Peking University, Beijing 100871 (China); LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Xue, C. [LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2011-07-15

290

Magnetic field sensors and visualizers using magnetic photonic crystals  

NASA Astrophysics Data System (ADS)

Magneto-optical imaging is widely used to observe the domain patterns in magnetic materials, visualize defects in ferromagnetic objects, and measure the spatial distribution of stray magnetic fields. Optimized 1D magneto-photonic crystals enable a significant increase in the sensitivity of magneto-optical sensors. The properties of such devices based on the optimized reflection (doubled Faraday rotation) mode and the use of 1D magnetic photonic crystals as sensors are discussed. Experimental results of the fabrication and characterization of ferrite-garnet layers possessing uniaxial magnetic anisotropy are shown, and an optimized film structure suitable for magneto-optical imaging is proposed.

Vasiliev, Mikhail; Alameh, Kamal E.; Kotov, Viatcheslav

2008-06-01

291

Magnetic power inverter: AC voltage generation from DC magnetic fields  

NASA Astrophysics Data System (ADS)

We propose a method that allows power conversion from DC magnetic fields to AC electric voltages using domain wall (DW) motion in ferromagnetic nanowires. The device concept relies on spinmotive force, voltage generation due to magnetization dynamics. Sinusoidal modulation of the nanowire width introduces a periodic potential for a DW, the gradient of which exerts variable pressure on the traveling DW. This results in time variation of the DW precession frequency and the associated voltage. Using a one-dimensional model, we show that the frequency and amplitude of the AC outputs can be tuned by the DC magnetic fields and wire-design.

Ieda, Jun'ichi; Maekawa, Sadamichi

2012-12-01

292

50-Hertz magnetic field and calcium transients in Jurkat cells: results of a research and public information dissemination (RAPID) program study.  

PubMed Central

An effect on intracellular calcium continues to be proposed as a biochemical pathway for the mediation of biologic effects of electrical-power-frequency magnetic fields (MF). However, reproducible results among laboratories are difficult to attain and the characteristics of magnetic field effects on intracellular free calcium ([Ca(2+)](i)) are not well understood. We attempted to repeat the studies of Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line by a Weak 50 Hz Magnetic Field. J Cell Physiol 156:395-398 (1993)] by investigating the effect of a 1.5-G 50-Hz MF on [Ca(2+)](i) in the Jurkat lymphocyte T-cell line. Changes in [Ca(2+)](i) were determined using microscopic imaging of fura-2 loaded Jurkat cells on poly-l-lysine-coated glass coverslips. The MF was generated by a single coil constructed with bifilar wire and located in the same plane as the cells. Cells were randomly exposed for 8 min to MF, sham field (SF), or no field (NF) conditions. The exposure condition remained coded until data analysis was complete. Each exposure period was preceded by an 8-min data collection to establish a baseline for [Ca(2+)](i). After each exposure condition, cells were exposed to anti-CD3 antibody that induced a rapid increase in [Ca(2+)](i) in responsive cells; this provided a positive control. [Ca(2+)](i) was analyzed for individual cells as spatially-averaged background-corrected 340/380 nm ratios, and a [Ca(2+)](i) transient was considered significant for positive deviations from baseline of 3 [multiple] an estimate of noise in the baseline. Typically, 25-50 cells/field were viewed and approximately 50% had no [Ca(2+)](i) transients in the baseline period and also responded to positive control. Only cells responding to positive control and lacking changes in [Ca(2+)](i) during the baseline period were considered qualified for assessment during the exposure period. The incidences of [Ca(2+)](i) transients during the exposure period for two experiments (40 [multiple] objective) were 16.5, 14.6, and 14.2% for MF, SF, and NF, respectively, and were not statistically significantly different. Previous studies by Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line after Exposure to Extremely-Low-Frequency Magnetic Fields with Variable Frequencies and Flux Densities. Bioelectromagnetics 16:41-47 (1995)] showed a high response rate (92%) for exposure to 1. 5-G 50-Hz MF when individual cells were preselected for investigation. We found no such effect when examining many cells simultaneously in a random and blind fashion. These results do not preclude an effect of MF on [Ca(2+)](i), but suggest that responsive cells, if they exist, were not identified using the approaches that we used in this study. Images Figure 1 Figure 2 Figure 3

Wey, H E; Conover, D P; Mathias, P; Toraason, M; Lotz, W G

2000-01-01

293

Modulating the Magnetic Field to Improve Magnetic Sensors  

NASA Astrophysics Data System (ADS)

The sensitivity of most magnetic sensors is affected by 1/f noise. Modulating the magnetic field to be detected by magnetic sensors can improve their performance by minimizing the effect of this 1/f noise and, in some cases, also have them operate in a narrow frequency band where they have higher sensitivity. We present approaches for modulating the field. One approach is the MEMS flux concentrator can be used with small magnetic sensors and another, based on using a rotating disc containing flux concentrators that can be used with large magnetic sensors, such as magnetoelectric sensors, that have an increased sensitivity at their mechanical resonance frequency. Sidebands observed around the modulation frequency demonstrate the applicability of these approaches. The MEMS flux concentrator has improved the signal to noise ratio in the power spectrum by a factor of 15. The sensors have the potential to achieve sensitivities of a few pT/Hz^1/2 at 1 Hz.

Edelstein, Alan; Petrie, Jonathan; Fine, Jonathan; Fischer, Greg; Burnette, James; Srinivasan, Gopal; Mandal, Sanjay

2011-03-01

294

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)

1997-05-01

295

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

296

Magnetically insulated opening switch research  

Microsoft Academic Search

We examine the feasibility of an opening switch concept based on magnetic insulation in a coaxial thermionic diode. It is found that the impedance ratio between closed and open states of the diode is marginal for efficient energy transfer via this type of switch. The open, or insulated state of the diode is characterized by current leakage across the magnetic

M. W. McGeoch; R. Kraft

1987-01-01

297

Magnetic field evolution in interacting galaxies  

Microsoft Academic Search

Aims: Violent gravitational interactions can change the morphologies of galaxies and, by means of merging, transform them into elliptical galaxies. We aim to investigate how they affect the evolution of galactic magnetic fields. Methods: We selected 16 systems of interacting galaxies with available VLA archive radio data at 4.86 and 1.4 GHz and compared their radio emission and estimated magnetic

R. T. Drzazga; K. T. Chyzy; W. Jurusik; K. Wiórkiewicz

2011-01-01

298

Magnetic field sensors for the industrial automation  

Microsoft Academic Search

The simple noncontacting detection of position plays a major role in the automation technique. Especially for the application in production plants, a high level of quality, reliability and durability is an absolute necessity. In this environment, the use of magnetic field sensors for detecting the position of a permanent magnet is at first glance a very well known and solved

T. Reininger; C. Hanisch

1997-01-01

299

The origin of galactic magnetic fields  

Microsoft Academic Search

There are two suggested origins for the observed galactic magnetic fields: the primordial origin and the dynamo origin. In this paper the dynamo origin is discussed and criticized. It is pointed out that if the interstellar medium, in which the dynamo operates, is infinitely conducting, the dynamo will not behave properly but will amplify the chaotic part of the magnetic

R. M. Kulsrud

1990-01-01

300

Bioeffects issues of power frequency magnetic fields  

Microsoft Academic Search

The recent release of two Swedish epidemiological studies correlating residential and occupational magnetic field exposures with certain cancers has strengthened the hypothesis that high voltage power delivery can increase the incidence of cancer. The studies have received wide television, radio, and newsmedia attention, and can be expected to influence public and governmental attitudes regarding residential and occupational 60-Hertz (Hz) magnetic

W. W. Shelton; J. C. Toler

1993-01-01

301

The Creation of Cosmic Magnetic Fields  

Microsoft Academic Search

In 1983, on the basis of Scriptures implying the original created material of the earth was water, I proposed that God created the water with the spins of its hydrogen nuclei initially aligned in one direction (Humphreys, 1983). That would produce a strong magnetic field. After 6,000 years of decay, including energy losses from magnetic reversals during the Genesis Flood,

D. Russell Humphreys

2008-01-01

302

Magnetic field generation by baroclinic waves  

Microsoft Academic Search

The general theory of the linear instabilities created by density differences in a rotating magnetic system is considered, and is applied to a plane layer stably stratified but with a slight superimposed horizontal density gradient that can give rise to baroclinic waves, modified by the presence of a horizontal co-rotating magnetic field parallel to the thermal wind. It is shown

S. I. Braginskii; P. H. Roberts

1975-01-01

303

MRS photodiode in strong magnetic field  

SciTech Connect

The experimental results on the performance of the MRS (Metal/Resistor/Semiconductor) photodiode in the strong magnetic field of 4.4T, and the possible impact of the quench of the magnet at 4.5T on sensor's operation are reported.

Beznosko, D.; Blazey, G.; Dyshkant, A.; Francis, K.; Kubik, D.; Rykalin, V.; /Northern Illinois U.; Tartaglia, M.A.; /Fermilab; Zutshi, v.; /Northern Illinois U.

2004-12-01

304

Toroidal Plasma Containment with Rotating Magnetic Field.  

National Technical Information Service (NTIS)

Experimental investigations were conducted on a toroidal plasma with alternating pinch- and theta-pinch magnetic fields as well as with a theta-pinch and with a screw pinch. For the alternating pinch, the resultant magnetic vector is rotating, so that the...

D. E. Brown H. G. Loos

1966-01-01

305

Biological effects due to weak magnetic field on plants  

NASA Astrophysics Data System (ADS)

Throughout the evolution process, Earth’s magnetic field (MF, about 50 ?T) was a natural component of the environment for living organisms. Biological objects, flying on planned long-term interplanetary missions, would experience much weaker magnetic fields, since galactic MF is known to be 0.1 1 nT. However, the role of weak magnetic fields and their influence on functioning of biological organisms are still insufficiently understood, and is actively studied. Numerous experiments with seedlings of different plant species placed in weak magnetic field have shown that the growth of their primary roots is inhibited during early germination stages in comparison with control. The proliferative activity and cell reproduction in meristem of plant roots are reduced in weak magnetic field. Cell reproductive cycle slows down due to the expansion of G1 phase in many plant species (and of G2 phase in flax and lentil roots), while other phases of cell cycle remain relatively stabile. In plant cells exposed to weak magnetic field, the functional activity of genome at early pre-replicate period is shown to decrease. Weak magnetic field causes intensification of protein synthesis and disintegration in plant roots. At ultrastructural level, changes in distribution of condensed chromatin and nucleolus compactization in nuclei, noticeable accumulation of lipid bodies, development of a lytic compartment (vacuoles, cytosegresomes and paramural bodies), and reduction of phytoferritin in plastids in meristem cells were observed in pea roots exposed to weak magnetic field. Mitochondria were found to be very sensitive to weak magnetic field: their size and relative volume in cells increase, matrix becomes electron-transparent, and cristae reduce. Cytochemical studies indicate that cells of plant roots exposed to weak magnetic field show Ca2+ over-saturation in all organelles and in cytoplasm unlike the control ones. The data presented suggest that prolonged exposures of plants to weak magnetic field may cause different biological effects at the cellular, tissue and organ levels. They may be functionally related to systems that regulate plant metabolism including the intracellular Ca2+ homeostasis. However, our understanding of very complex fundamental mechanisms and sites of interactions between weak magnetic fields and biological systems is still incomplete and still deserve strong research efforts.

Belyavskaya, N. A.

2004-01-01

306

Effects of Magnetic Field on Biological Cells and Applications  

NASA Astrophysics Data System (ADS)

While there has been extensive research performed in the physics of magnetic fields and the physics and chemistry in life sciences, independent of each other, there has been a paucity of scientific research and development investigating the possible applications of magnetic fields in life sciences. The focus of this presentation is to present the stimulation mechanism by which magnetic fields affect (a) yeast cells (b) plant cells and (c) mammalian normal and cancer cells. Recently we have found that the Saccharomyces Cerevsa yeast growth increases by about 30to a 1 tesla field and the production of CO2 increases by about 30of yeast metabolism may be due to an increase in intercellular interaction and protein channel alignment, the introduction of an alteration in the DNA from the magnetic field exposure or a combination of these mechanisms. We also have found that the application of high magnetic fields (1 tesla and above) can have marked effects on the germination and growth of plants, especially corn, beans and peas. This finding has opened up the possibility of technology developments in botanical growth systems to accelerate seed germination and crop harvesting. Most recently we have investigated the application of high magnetic fields on leukemia, CaCoII and HEP G2 cancer cell lines. We found that when leukemia are exposed to a 12 tesla field for 2 hours has an increase in cell death by about 30that were not exposed to the magnetic field. Viability of CaCoII cells sandwiched between permanent magnets of maximum strength of 1.2 tesla was measured. A decrease in viable cells by 33unexposed cells. HSP 70 was measured for HEPG2 cells that were exposed to permanent magnetic field of 1.2 tesla for 40 minutes and for unexposed cells. It was found that the exposed cells produce 19 times more HSP70 compared to unexposed cells. Our results together with other investigators report suggest a strong evidence of a reduction in the cell growth rate for cancer cells when subjected to high magnetic field. Devices that utilize an applied steady magnetic filed in it operation such as devices for blood component separation and diagnostic sensors have been developed.

Chen, Ching-Jen

2001-03-01

307

Fractal structure of the interplanetary magnetic field  

SciTech Connect

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.

1985-05-01

308

Magnetic field calculation on CDF detector (I)  

SciTech Connect

Magnetic field and flux distribution for the CDF detector is calculated using a TRIM program. The flux distribution in the system is calculated at several different excitation levels with an expected B-H curve.

Yamada, R.

1983-01-20

309

Magnetic field dragging in accretion discs  

NASA Astrophysics Data System (ADS)

Accretion discs are composed of ionized gas in motion around a central object. Sometimes, the disc is the source of powerful bipolar jets along its rotation axis. Theoretical models invoke the existence of a bipolar magnetic field crossing the disc and require two conditions to produce powerful jets: field lines need to be bent enough at the disc surface and the magnetic field needs to be close to equipartition. The work of Petrucci et al (2008) on the variability of X-ray binaries supposes that transitions between pure accretion phases and accretion-ejection phases are due to some variations of the disc magnetization. This rises the problem of the magnetic field dragging in accretion discs. We revisit the method developed by Lubow et al (1994) by including momentum and mass conservation equations in a time-dependent 1D MHD code.

de Guiran, R.; Ferreira, J.

2010-12-01

310

Magnetic Fields in Solar Active Regions.  

National Technical Information Service (NTIS)

The report is a review and interpretation of solar active region observations obtained principally with magnetographs. Most of these instruments measure the line-of-sight component of the magnetic field. A few instruments can also measure the transverse c...

D. M. Rust

1970-01-01

311

Turbulent Diffusion in a Magnetic Field.  

National Technical Information Service (NTIS)

The turbulent diffusion in a magnetic field is studied. The special case where the turbulence is caused by non collisionnal drif instabilities is considered in some detail. (Atomindex citation 11:495636)

P. Rolland

1978-01-01

312

Faraday's Law Problem: Describing Magnetic Fields  

NSDL National Science Digital Library

A loop of wire travels from the right to the left through an inhomogeneous magnetic field. (The green line is at x=0 is for your reference.) The induced emf in the loop is shown in Volts in the animation.

Christian, Wolfgang; Belloni, Mario

2007-03-03

313

Homogeneous Viscous Universes with Magnetic Field.  

National Technical Information Service (NTIS)

In this thesis homogeneous universes are studied containing a large scale magnetic field. In the evolution three different phases are distinguished: the lepton, the plasma and the matter dominated eras. During the lepton and plasma eras, which form the ra...

G. A. Q. Salvati

1986-01-01

314

Earth's Magnetic Field in the past.  

National Technical Information Service (NTIS)

Variations of the Earth's magnetic field in the past are known because they were recorded in various ferrimagnetic minerals such as titanomagnetite and maghemite. This article describes the principal techniques and sample materials (volcanic lava, sedimen...

D. J. R. Nordemann

1982-01-01

315

Aging beryllium bronze in pulsed magnetic fields  

NASA Astrophysics Data System (ADS)

Methods of microhardness and X-ray diffraction were used to study the kinetics of changes in the microstructure of the beryllium bronze alloy BrB-2 in the process of decomposition of the supersaturated solid solution in a pulsed magnetic field with a frequency from 0 to 7 Hz at an amplitude of the pulse of 318.4 kA/m, a dc component of the magnetic field equal to 238.8 kA/m, at a temperature of 350°C and annealing duration of 1 h. Frequency dependences of the microhardness, lattice parameter, concentration of beryllium in the residual matrix, size of coherent domains, dislocation density, and relative microdeformations of mosaic blocks in the matrix have been measured upon aging with and without pulse magnetic field. The results of experiments show that the pulse magnetic field substantially affects the parameters of the fine structure and physicomechanical properties of the bronze.

Osinskaya, Yu. V.; Pokoev, A. V.

2008-04-01

316

Heat Capacity Measurements in Pulsed Magnetic Fields  

SciTech Connect

The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 45 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool.

Jaime, M.; Movshovich, R.; Sarrao, J.L.; Kim, J.; Stewart, G.; Beyermann, W.P.; Canfield, P.C.

1998-10-23

317

Electric and magnetic field reduction by alternative transmission line options  

SciTech Connect

Ground level electric, and more recently magnetic, fields from overhead power transmission lines are increasingly important considerations in right of way specification, with states setting or planning to set edge of right of way limits. Research has been conducted in high phase order power transmission wherein six of twelve phases are used to transmit power in less physical space and with reduced electrical environmental effects than conventional designs. The first magnetic field testing, as reported in this paper, has verified predictive methods for determination of magnetic fields from high phase order lines. Based on these analytical methods, field profiles have been determined for lines of different phase order of comparable power capacity. Potential advantages of high phase order as a means of field mitigation are discussed. 10 refs., 12 figs., 3 tabs.

Stewart, J.R. (Power Technologies, Inc., Schenectady, NY (United States)); Dale, S.J. (Oak Ridge National Lab., TN (United States)); Klein, K.W. (Energetics, Inc., Columbia, MD (United States))

1991-01-01

318

Study of weak solar magnetic fields  

NASA Astrophysics Data System (ADS)

There have been two major gains in this period: first, the completion and analysis of round-the-clock observations in cooperation with the Huairou Observatory in the People's Republic of China, which enabled us to obtained the first longterm observations of weak solar magnetic fields, and the application of the magneto-optic filter to the measurement of magnetic fields. The observations in collaboration with China have enabled us to make observations for as long as seven days of solar magnetic regions, with only short interruptions when the sun could not be seen from the U.S. and China. The stronger elements of the chromospheric network are rather long lived, lasting about 70 hours. In fact, it is possible that they last longer, because although the shape changes, it is often possible to still identify a magnetic entity. The second important result was that one could find definite evidence of magnetic field cancellation occurring after solar flares. The increased time coverage enabled us to check the evolution of the magnetic fields during this period. The other development, the use of the magneto-optic filter, is full of promise for the future. This filter is made by using a glass tube filled with potassium which is placed in a strong magnetic field.

Zirin, Harold

319

Magnetic tunnel junctions for low magnetic field sensing  

NASA Astrophysics Data System (ADS)

In this thesis, we did a comprehensive investigation on the relationship between spin-dependent tunneling and structural variation in junction devices. Magnetic, microstructural, and transport studies have shown a significant improvement in exchange-bias, a reduced barrier roughness, and an enhanced magnetoresistance for samples after magnetic annealing. We have examined different magnetic configurations required for sensing applications and presented some results of using MTJ sensors to detect AC magnetic fields created by electrical current flow and DC stray field distributions of patterned magnetic materials. We have studied the low frequency noise in MTJ sensors. We have found that the 1/f noise in MTJs has magnetic as well as electrical origins, and is strongly affected by the junction's internal structure. The magnetic noise comes from magnetization fluctuations in the free FM layer and can be understood using the fluctuation-dissipation theorem. While the field-independent electrical noise due to charge trapping in the barrier, is observed in the less optimized MTJs sensors, and has an amplitude at least one order of magnitude higher than the noise component due to magnetization fluctuations. In addition, we have studied the magnetization switching of Cobalt rings with varying anisotropy utilizing scanning magnetoresistive microscopy. We have for the first time observed a complicated multi-domain intermediate phase during the transition between onion states for samples with strong anisotropy. This is in contrast to as deposited samples, which reverse by simple domain wall motion and feature an intermediate vortex state. The result is further analyzed by micro magnetic simulations.

Liu, Xiaoyong

320

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. II. Armature-reaction field  

Microsoft Academic Search

For pt.I see ibid., vol.29, no.1, p.124-135 (1993). An analytical technique for predicting the open-circuit magnetic field distribution in the airgap\\/magnet region of a brushless permanent-magnet DC motor equipped with a surface mounted magnet rotor and a slotless stator was presented in Pt.I. In the present work, the analysis is extended to the prediction of the armature reaction field produced

Z. Q. Zhu; David Howe

1993-01-01

321

Mean-field quantum dynamics with magnetic fields  

NASA Astrophysics Data System (ADS)

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 Schrödinger equation converges to the projection onto the solution of the magnetic Hartree equation in trace norm and in energy as N --> ?. Estimates on the rate of convergence are provided.

Lührmann, Jonas

2012-02-01

322

An Intergalactic Magnetic Field from Quasar Outflows  

Microsoft Academic Search

Outflows from quasars inevitably pollute the intergalactic medium (IGM) with\\u000amagnetic fields. The short-lived activity of a quasar leaves behind an\\u000aexpanding magnetized bubble in the IGM. We model the expansion of the remnant\\u000aquasar bubbles and calculate their distribution as a function magnetic field\\u000astrength at different redshifts. We find that by a redshift z ~ 3, about 5-80%

Steven R. Furlanetto; Abraham Loeb

2001-01-01

323

Strain Sensors for High Field Pulse Magnets  

Microsoft Academic Search

\\u000a In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical\\u000a deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic\\u000a temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective\\u000a of this preliminary study

Christian Martinez; Yan Zheng; Daniel Easton; Kevin M Farinholt

2009-01-01

324

Effects of static magnetic fields on plants  

Microsoft Academic Search

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 (Delta ≊ < 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

O. Kuznetsov

2004-01-01

325

Magnetic fields and the nova outburst  

Microsoft Academic Search

Surface magnetic fields of approx.10⁶⁻⁻¹°sup 7\\/ gauss have been inferred from polarization observations of the old nova DQ Her. Such strong magnetic fields will probably lead to corotation of the core and envelope of the white dwarf. Assuming a rotation period of 142 s, this corotation will lead to centrifugal forces sufficient to counterbalance gravity as the star's envelope expands

W. K. Rose; E. H. Scott

1976-01-01

326

Growing Magnetic Fields in Central Compact Objects  

NASA Astrophysics Data System (ADS)

We study the effects of growth models of magnetic fields in Central Compact Objects (CCOs). Such a field evolution is not a new idea (Blandford, Applegate, & Hernquist 1983) but the evolutionary implications not have been followed up completely (Michel 1994). We discussed the new class of neutron stars which belong to five main types that have mainly been recognized in the last ten years. The possibility that a rapid weakly magnetized pulsar might have formed in SN1987A is commented.

Bernal, C. G.; Page, D.

2011-10-01

327

Parallel heat transport in integrable and chaotic magnetic fields  

SciTech Connect

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

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

2012-05-15

328

Parallel heat transport in integrable and chaotic magnetic fields  

SciTech Connect

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

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

2012-01-01

329

Magnetic Field Problem: Mesuring Current in Wire  

NSDL National Science Digital Library

A wire carrying an unknown current is shown above. An external magnetic field that has constant magnitude and direction is applied to the top half of the simulation (The gray rectangle is at the boundary for your reference). In addition, there is the magnetic field produced by the current in the wire. The direction arrows show the vector sum of these two fields. (The color of the direction arrows represents the magnitude of the field as before.) Observe the force vector and the force/length in the yellow message box in the lower left hand corner.

Christian, Wolfgang; Belloni, Mario

2007-03-03

330

Effects of Magnetic Field on Classical Ionization  

NASA Astrophysics Data System (ADS)

Classical equations of motion are solved numerically for one electron atoms in an intense laser pulse. The study investigates the influence of the laser magnetic field on ionization and rescattering. Many models of electron ionization have ignored the magnetic field of the laser pulse, but recent work has looked at the magnetic field's role in stabilization [1]. Work has been done to show that in the ultra-strong regime (intensities of ˜10^18 W/cm^2) the laser magnetic field has an influence on rescattering [2]. Specifically, drift of the ionized electron along the laser propagation direction. We use a classical model of the atom, atomic number Z, with one electron and numerically integrate two sets of equations of motion, those with and those without the laser magnetic field. Observable quantities, such as electron radius and energy, are calculated and compared. The data shows that the laser magnetic field does have some influence on ionization, specifically on electron dynamics before ionization and the time required for ionization.[4pt] [1] L. N. Gaier and C. H. Keitel, PRA 65, 023406 (2002).[0pt] [2] S. Palaniyappan, I. Ghebregziabher, A. Dichiara, J. MacDonald, and B. C. Walker, PRA 74, 033403 (2006).

Grugan, Patrick; Videtto, Michael; Mancuso, Christopher; Luo, Sui; Walker, Barry

2011-06-01

331

Characteristics of the magnetic field distribution on compact NMR magnets using cryocooled HTS bulks  

NASA Astrophysics Data System (ADS)

Recently, the performance of high temperature superconducting (HTS) bulks such as critical current density, size, and mechanical strength has been improved rapidly. So, various applications using HTS bulks such as motors, bearings and flywheels have been investigated by many research groups. A compact nuclear magnetic resonance (NMR) magnet is one of the new applications after a technique to enhance maximum trapped field of the HTS bulk more than 11.7 T (500 MHz 1H NMR frequency) has been developed. This new compact NMR magnet out of HTS bulks is cost-effective compared with conventional NMR magnets and then expected to be widely used in food and drug industry. In design and manufacture of the compact NMR magnets, spatial field homogeneity of the large trapped magnetic field in HTS bulk annuli is a crucial issue because the behavior of a trapped field is highly non-linear and, as a result, a technique to improve the field homogeneity such as active/passive shimming now becomes more challenging compared with that of the conventional counterparts. This paper presents the magnetic field distributions in single and three assembled HTS bulk annuli measured by a 3-axis and multi-arrayed Hall sensor under two different cryogenic environments: (1) in a bath of liquid nitrogen (LN2) and (2) dry cooling by a cryocooler. The spatial homogeneity changes with various operating temperatures were investigated and the effect of critical current density enhancement by lowering the operating temperature on the field homogeneity improvement was discussed in detail.

Kim, S. B.; Takano, R.; Nakano, T.; Imai, M.; Hahn, S. Y.

2009-10-01

332

In-plane magnetic field dependence of electric field-induced magnetization switching  

NASA Astrophysics Data System (ADS)

Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin equation, and possible factors determining the probability are discussed.

Kanai, S.; Nakatani, Y.; Yamanouchi, M.; Ikeda, S.; Matsukura, F.; Ohno, H.

2013-08-01

333

Measurement of magnetic field using collaborative AUVs  

Microsoft Academic Search

This paper describes an effort to adapt a fleet of autonomous underwater vehicles (AUVs) for the measurement of the magnetic signature of surface ships. Currently, two such vehicles have been upgraded with the necessary navigation and measurement hardware to perform magnetic measurements. Initial testing has been performed at the Naval Acoustic Research Detachment at Lake Pend Oreille, Idaho. Two vehicles

Jesse Pentzer; Brendan Crosbie; Thomas Bean; John Canning; James Frenzel; Michael Anderson; Dean Edwards

2010-01-01

334

Tracking a Jurassic reversal of the Earth's magnetic field  

NASA Astrophysics Data System (ADS)

Roughly 180 million years ago, during the height of the Jurassic period, the Earth's magnetic field flipped, bringing the magnetic north pole once again into the Northern Hemisphere. This so-called van Zijl reversal, named for the researcher who first described it, is the second-oldest well-documented geomagnetic reversal. Such perturbations of the Earth's magnetic field, which tend to take place over about 10,000 years but possibly much less, have been identified as occurring up to several billion years ago and as recently as 780,000 years ago. An open question exists about the effect of such reversals on the properties of the Earth's magnetic field, including the structure it takes, and the consequent effects on its shape, size, and strength.

Schultz, Colin

2012-04-01

335

Instantaneous magnetic field distribution in brushless permanent magnet DC motors. I. Open-circuit field  

Microsoft Academic Search

An analytical technique for predicting the instantaneous magnetic field distribution in the airgap region of radial-field topologies of brushless permanent-magnet DC motors, under any specified load condition and accounting implicitly for the stator winding current waveform and the effect of stator-slot-openings, has been developed. It is based on the superposition of the component fields due to the permanent magnet and

Z. Q. Zhu; David Howe; Ekkehard Bolte; Bemd Ackermann

1993-01-01

336

Earth magnetic field effects on Swarm electric field instrument  

NASA Astrophysics Data System (ADS)

Earth magnetic field effects on the particle sensors carried by the Swarm satellites are investigated using particle in cell (PIC) and test-particle modelling. In the reference frame of the spacecraft in which plasma flows at relative velocity v?, Earth magnetic field leads to an ambient electric field E?=-v?×B?, which affects the shape of particle distribution functions at the particle sensors. This in turn impacts the distribution of particle fluxes on the microchannel plate (MCP) in the ram face mounted thermal ion imagers (TIIs). Shifts in the centroid of these distributions depend on the direction and magnitude of the local magnetic field and, as such, are expected to vary periodically along the spacecraft orbit. The magnitude of these shifts is estimated quantitatively, and the effect of their variation on the calibration and interpretation of the electric field instrument (EFI) are also discussed.

Rehman, S.; Burchill, J.; Eriksson, A.; Marchand, R.

2012-12-01

337

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.

338

Critical Magnetic Field Determination of Superconducting Materials  

SciTech Connect

Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

2011-11-04

339

Ion pump using cylindrically symmetric spindle magnetic field  

NASA Astrophysics Data System (ADS)

For all accelerators and many research and industries, excellent vacuum conditions are required and the highest possible pumping rates are necessary. For most applications the standard ion sputtering pump (ISP) meets these requirements and is optimal for financial point of view also. The physical principle of the ISP is well known and many companies manufacture variety of ISP. Most of them use dipole magnetic field produced by permanent magnet and electric dipole field between the electrodes in which tenuous plasma is created because of interaction of between the relatively fast electrons slow residual gas atoms. Performance of an ISP depends basically on the electron cloud density in between the titanium electrodes but in the available present configurations no consideration has been given to electron confinement which needs a mirror magnetic field. If this is incorporated it will make a robust ISP surely; furthermore, the requirement of constant feeding of high voltage to electrodes for supplying sufficient number of electrons will be reduced too. A study has been performed to create sufficient rotationally symmetric spindle magnetic field (SMF) with inherent presence of magnetic mirror effect to electron motion to confine them for longer time for enhancing the density of electron cloud between the electrodes. It will lessen the electric power feeding the electrodes and lengthen their life-time. Construction of further compact and robust ISP is envisaged herein. The field simulation using the commercially available permanent magnet together with simulation of electron motion in such field will be presented and discussed in the paper.

Rashid, M. H.

2012-11-01

340

Instantons and Sphalerons in a Magnetic Field  

NASA Astrophysics Data System (ADS)

I study the properties of the Euclidean Dirac equation for a light fermion in the presence of both a constant abelian magnetic field and an SU(2) instanton. In particular, I analyze the zero modes analytically in various limits, in order to compare with recent lattice QCD results, and study the implications for the electric dipole moment of the instanton induced by the magnetic field. I also present a holographic computation of the sphaleron rate of a strongly coupled plasma in a the presence of a constant magnetic flux and discuss its physical implications on heavy ion collisions.

Ba?ar, Gökçe; Dunne, Gerald V.; Kharzeev, Dmitri E.

2013-05-01

341

Asymptotic freedom in strong magnetic fields.  

PubMed

Perturbative gluon exchange interaction between quark and antiquark, or in a 3q system, is enhanced in a magnetic field and may cause vanishing of the total qq[over ¯] or 3q mass, and even unlimited decrease of it-recently called the magnetic collapse of QCD. The analysis of the one-loop correction below shows a considerable softening of this phenomenon due to qq[over ¯] loop contribution, similar to the Coulomb case of QED, leading to approximately logarithmic damping of gluon exchange interaction (?O(1/ln|eB|)) at large magnetic field. PMID:23679595

Andreichikov, M A; Orlovsky, V D; Simonov, Yu A

2013-04-18

342

Superconducting Magnet Facility for Plasma Physics Research  

Microsoft Academic Search

A superconducting magnet facility has recently been built and operated as an adjunct to a plasma physics experiment. The facility consists of two superconducting coils in a variable-spacing, horizontal-axis, split-pair configuration. Both coils are enclosed in Dewars that allow a working magnetic field diameter of 17.8 cm at the necks of the magnetic bottle. Each coil is capable of producing

J. Reece Roth; Donald C. Freeman; David A. Haid

1965-01-01

343

Effects of Electric and Magnetic Field on Freezing and Possible Relevance in Freeze Drying  

Microsoft Academic Search

Application of an electric or magnetic field can significantly affect the freezing characteristics of water. A DC electric field will tend to induce ice nucleation at a lower degree of supercooling, and there is evidence to show that an AC electric field delays the onset of ice nucleation. Industrial research has shown that a magnetic field can be used to

M. W. Woo; A. S. Mujumdar

2010-01-01

344

Laminated Magnet Field Coil Sheath.  

National Technical Information Service (NTIS)

A method is disclosed 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...

J. R. Skaritka

1987-01-01

345

Reconnection rates of magnetic fields  

Microsoft Academic Search

The Sweet-Parker and Petschek scalings of magnetic reconnection rate are modified to include the effect of the viscosity. The modified scalings show that the viscous effect can be important in high-..beta.. plasmas. The theoretical reconnection scalings are compared with numerical simulation results in a tokamak geometry for three different cases: a forced reconnection driven by external coils, the nonlinear m

D. A. Monticello; R. B. White

1983-01-01

346

Magnetic Field Generation by Relativistic Shear Flows  

NASA Astrophysics Data System (ADS)

We report PIC simulation results of magnetic field generation by relativistic shear flows. We find that the shear flow boundary layer in initially non-magnetic shear flows is unstable to the growth of oblique 2-stream and Weibel instabilities near the boundary layer. Such instabilities generate current sheets and loops which eventually form nonlinear ordered structures resembling magnetic flux tubes with alternating polarity, orthogonal to the shear flow direction. Peak magnetic fields can reach almost equipartition values. The size and amplitude of such magnetic structures reach a steady state when the free energy input of the shear flow is balanced by turbulence dissipation. Nonthermal particles are efficiently accelerated, likely by the drift-kink instability, into a power-law energy distribution. These results have important implications for many astrophysical settings, including multi-component blazar jets and gamma-ray bursts. This work was supported by NSF AST0909167 and NASA Fermi grants.

Liang, Edison; Boettcher, Markus; Smith, Ian

2011-11-01

347

Functional Magnetic Resonance Imaging in Nursing Research  

Microsoft Academic Search

Functional magnetic resonance imaging (fMRI) is a powerful noninvasive neuroimaging technique nurse scientists can use to investigate the structure and cognitive capacities of the brain. A strong magnetic field and intermittent high-frequency pulses cause protons in body tissues to release energy, which can be recorded and processed into images that are sensitive to specific tissue characteristics. Although temporal and spatial

L. Clark Johnson; Todd L. Richards; Kristen H. Archbold; Carol A. Landis

2006-01-01

348

Validate Mapping of Internal Lunar Magnetic Field  

NASA Astrophysics Data System (ADS)

In this work we present a global mapping of vector lunar magnetic field based on new method of separation of internal and external fields using inversion. The magnetic measurements collected during the lifetime of Lunar Prospector (LP) extended mission during 1999 were strongly disturbed by the solar wind, a period which coincided with a maximum of the 23 cycle activity. The multi scale wavelength external fields were analyzed using spherical harmonic transform. The external field determined by inversion was then removed from each magnetic field component for each half orbit. To map the vector magnetic crustal anomalies, all LP magnetometer data collected at low altitudes in the three different lunar environments: (1) geomagnetic tail (2) solar wind (3) geomagnetic sheath, were processed using this new approach. The results obtained using these selection criteria allow us to get a global coverage of the lunar surface by the vector magnetic field at variable spacecraft low altitudes. To validate our mapping we have developed and applied a method based on properties of potential fields functions. This method can be used to determine both horizontal North and East components using only vertical component. The validate lunar internal magnetic measurements obtained at variable spacecraft altitudes was then continued to a common altitude of 30 km using non linear inverse methods. This mapping confirm firstly the nature of the crustal sources of lunar magnetic field and clearly shows that the strongest concentrations of anomalies are associated with of high albedo and/or located antipodal to large young basins (Orientale, Serenitatis, Imbrium, and Crisium) of age about 3.9 Ga.

Berguig, M. C.; Hamoudi, M.; LeMouël, J. L.; Cohen, Y.

2012-04-01

349

Effect of magnetic field cooling and magnetization anomaly in magnetic fluids near melting point  

Microsoft Academic Search

The magnetization process of ferrofluids with carrier fluids of water, paraffin, and alkylnaphtalene was investigated in a temperature range from 77 to 300 K as functions of the freezing rate and the intensity of cooling magnetic fields. A uniaxial magnetic anisotropy is induced by field cooling in frozen ferrofluids. This induced anisotropy which is caused by the formation of clustering

H. Miyajima; N. Inaba; S. Taketomi; M. Sakurai; S. Chikazumi

1988-01-01

350

Magnetic Field Analysis of a Permanent-Magnet Induction Generator  

NASA Astrophysics Data System (ADS)

The permanent-magnet induction generator (PMIG) is a new type of induction machine that has a permanent-magnet rotor inside a squirrel-cage rotor. In this paper, a new technique for the magnetic field analysis of the PMIG is proposed. The proposed technique is based on the PMIG's equivalent circuit and the two-dimensional finite-element analysis (2D-FEA). To execute the 2D-FEA, the phasors of primary and secondary currents are calculated from the equivalent circuit, and the input data for the 2D-FEA is found by converting these phasors into the space vectors. As a result, the internal magnetic fields of the PMIG can be easily analyzed without complicated calculations.

Tsuda, Toshihiro; Fukami, Tadashi; Kanamaru, Yasunori; Miyamoto, Toshio

351

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

352

Magnetic field effects on CRT computer monitors  

Microsoft Academic Search

Summary form only as given. 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

B. Banfai; G. G. Karady; C. J. Kim; K. Maracas

1999-01-01

353

Intergalactic magnetic fields and structure formation  

Microsoft Academic Search

The observational evidence for magnetic fields in clusters of galaxies will be briefly reviewed. It is possible such fields are stongly affected by gas dynamical processes driven by, e.g., cluster mergers. Numerical MHD investigations of such processes, as well as studies of the role of MHD processes affecting large scale structure formation, will be reviewed.

J. M. Stone

2000-01-01

354

The Magnetic Field of beta Coronae Borealis.  

National Technical Information Service (NTIS)

Measurements of resolved Zeeman patterns in the spectrum of Beta CrB show that /H(s)/, the mean surface magnetic field, varies approximately 180 degrees out of phase with the longitudinal component of the field H(e). The maximum observed /H(s)/ is about 5...

S. C. Wolff R. J. Wolff

1969-01-01

355

Magnetic Field Problem: Wires Carrying Current  

NSDL National Science Digital Library

A cross section of three wires carrying unknown currents is shown above. You can double-click anywhere inside the animation to draw a magnetic field line. You can also click-drag the wires but this will erase any field line that you have drawn.

Christian, Wolfgang; Belloni, Mario

2007-03-03

356

The production of Ganymede's magnetic field  

Microsoft Academic Search

One of the great discoveries of NASA's Galileo mission was the presence of an intrinsically produced magnetic field at Ganymede. Generation of the relatively strong (750 nT) field likely requires dynamo action in Ganymede's metallic core, but how such a dynamo has been maintained into the present epoch remains uncertain. Using a one-dimensional, three layer thermal model of Ganymede, we

Michael T. Bland; Adam P. Showman; Gabriel Tobie

2008-01-01

357

Relationship between the magnetic hyperfine field and the magnetic moment  

Microsoft Academic Search

Based on experimental data it is shown, for some chosen alloys and compounds of iron, that there is no one unique relationship between the 57Fe-site magnetic hyperfine field, Bhf, and the magnetic moment per Fe atom, m. Instead, the Bhf-m plot consists of several branches, each of them being characteristic of a given alloy or compound. Consequently, the effective proportionality

S. M. Dubiel

2008-01-01

358

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

359

Varying electromagnetic coupling and primordial magnetic fields  

SciTech Connect

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 can minimum seed fields 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.

Bertolami, O.; Monteiro, R. [Departamento de Fisica, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisbon (Portugal)

2005-06-15

360

Primordial magnetic fields and nonlinear electrodynamics  

SciTech Connect

The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by Lagrangians having a power-law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.

Kunze, Kerstin E. [Departamento de Fisica Fundamental, and Instituto Universitario de Fisica Fundamental y Matematicas (IUFFyM), Universidad de Salamanca, Plaza de la Merced s/n, E-37008 Salamanca (Spain)

2008-01-15

361

The United States National High Magnetic Field Laboratory: Facilities, science and technology  

Microsoft Academic Search

The United States National High Magnetic Field Laboratory (NHMFL) is operated by the University of Florida, Florida State University and the Los Alamos National Laboratory and has been charged to develop and maintain advanced magnet systems in response to the research needs of a diverse user community, to advance the development of magnet and magnet materials technology and to promote

J. E. Crow; D. M. Parkin; H. J. Schneider-Muntau; N. S. Sullivan

1996-01-01

362

Strong CP violation in external magnetic fields  

SciTech Connect

We study the response of the QCD vacuum to an external magnetic field, in the presence of strong CP violation. Using chiral perturbation theory and large N{sub c} expansion, we show that the external field would polarize quantum fluctuations and induce an electric dipole moment of the vacuum along the direction of the magnetic field. We estimate the magnitude of this effect in different physical scenarios. In particular, we find that the polarization induced by the magnetic field of a magnetar could accelerate electric charges up to energies of the order {approx}{theta}10{sup 3} TeV. We also suggest a connection with the possible existence of ''hot-spots'' on the surface of neutron stars.

Millo, R. [Dipartimento di Fisica, Universita degli Studi di Trento, Via Sommarive 15, Povo (Trento) 38050 (Italy); Faccioli, P. [Dipartimento di Fisica, Universita degli Studi di Trento, Via Sommarive 15, Povo (Trento) 38050 (Italy); I.N.F.N., Gruppo Collegato di Trento, Via Sommarive 15, Povo (Trento), 38050 (Italy)

2008-03-15

363

Compute Values of Earth's Magnetic Field  

NSDL National Science Digital Library

The program run from this form computes the values of the Earth's magnetic field parameters for a given location and date or date range. Input required is the date and location (in latitude and longitude) of interest. Links to the U.S. Census Bureau's U.S. Gazeteer and the Getty Thesaurus assists in determing the latitude and longitude for locations of interest. The magnetic parameters (D, I, H, X, Y, Z, and F) are computed based on the latest International Geomagnetic Reference Field (IGRF), a Schmidt quasinormalized spherical harmonic model of the magnetic field. Accuracies for the angular components (Declination, D and Inclination, I) are reported in degrees and minutes of arc and are generally within 30 minutes. Accuracies for the force components (Horizontal - H, North - X, East - Y, Vertical - Z, and Total force - F) are generally within 25 nanotesla. A link to frequently-asked questions about the geomagnetic field of Earth is provided as background material.

364

Intermittent character of interplanetary magnetic field fluctuations  

SciTech Connect

Interplanetary magnetic field magnitude fluctuations are notoriously more intermittent than velocity fluctuations in both fast and slow wind. This behavior has been interpreted in terms of the anomalous scaling observed in passive scalars in fully developed hydrodynamic turbulence. In this paper, the strong intermittent nature of the interplanetary magnetic field is briefly discussed comparing results performed during different phases of the solar cycle. The scaling properties of the interplanetary magnetic field magnitude show solar cycle variation that can be distinguished in the scaling exponents revealed by structure functions. The scaling exponents observed around the solar maximum coincide, within the errors, to those measured for passive scalars in hydrodynamic turbulence. However, it is also found that the values are not universal in the sense that the solar cycle variation may be reflected in dependence on the structure of the velocity field.

Bruno, Roberto; Carbone, Vincenzo; Chapman, Sandra; Hnat, Bogdan; Noullez, Alain; Sorriso-Valvo, Luca [IFSI/INAF, via Fosso del Cavaliere, I-00133 Rome (Italy); Dipartimento di Fisica, Universita della Calabria, and CNISM, Unita di Cosenza, Arcavacata di Rende I-87036 (Italy); Centre for Fusion, Space and Astrophysics, University of Warwick, Warwick CV4 7AL (United Kingdom); Observatoire de la Cote d'Azur, Boulevard de l'Observatoire, F-06304 Nice (France); LICRYL, INFM/CNR, I-87036 Arcavacata di Rende (Italy)

2007-03-15

365

Trajectories in Electric and Magnetic Fields Model  

NSDL National Science Digital Library

The Trajectories in Electric and Magnetic Fields model computes a family of trajectories of charges emitted from a point source isotropically and with the same energy. These trajectories create focal points and caustic surfaces meeting the symmetry line in conical cusps. The simulation enables users to study these trajectories in both crossed and parallel magnetic fields. The user can vary the initial particle velocity and the field strengths. The Trajectories in Electric and Magnetic Fields model was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item.

Christian, Wolfgang

2012-10-25

366

Field research, 1993-1994  

SciTech Connect

This article summarizes field research during the 1993-94 field season in the Antarctic. Among other studies were descriptions of the following: Effects of ultraviolet radiation on the photosynthesis of phytoplankton in the antarctic marginal ice zone; Long-term ecological research (LTER) on the Antarctic marine ecosystem: microbiology and carbon flux; Geologic record of late Wisconsinan/Holocene ice sheet advance and retreat from the Ross Sea; Late Quarernary paleoclimatic history of southern Chile: evidence from the marine record; Integrated biostratigraphy and high resolution seismic stratigraphy of the Ross Sea: Implications for Cenozoic eustatic and climate change; Oxygen-isotope record from McMurdo dome and its relation to the geological climate record of the McMurdo Dry Valleys; Evaluation of processes at polar glacier grounding lines to constrain glaciological and oceanographic models; Reconstruction of paleotemperatures from precision borehole temperature logging; Cenozoic glacial and climatic history of the antarctic region; Observation and modeling studies of episodic events in the south polar atmospheric boundary layer; biogeochemistry of carbon and silica on the antarctic shelf; Chlorine and bromine containing trace gases in Antarctica; South Pole monitoring for climatic change; Aerosol Sampling at Palmer Station; several Ozone depletion studies.

Not Available

1993-09-01

367

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

368

Magnetic clouds and force-free fields with constant alpha  

Microsoft Academic Search

Magnetic clouds observed at 1 AU are modeled as cylindrically symmetric, constant alpha force-free magnetic fields. The model satisfactorily explains the types of variations of the magnetic field direction that are observed as a magnetic cloud moves past a spacecraft in terms of the possible orientations of the axis of a magnetic cloud. The model also explains why the magnetic

L. F. Burlaga

1988-01-01

369

Tailoring magnetic field gradient design to magnet cryostat geometry.  

PubMed

Eddy currents induced within a magnetic resonance imaging (MRI) cryostat bore during pulsing of gradient coils can be applied constructively together with the gradient currents that generate them, to obtain good quality gradient uniformities within a specified imaging volume over time. This can be achieved by simultaneously optimizing the spatial distribution and temporal pre-emphasis of the gradient coil current, to account for the spatial and temporal variation of the secondary magnetic fields due to the induced eddy currents. This method allows the tailored design of gradient coil/magnet configurations and consequent engineering trade-offs. To compute the transient eddy currents within a realistic cryostat vessel, a low-frequency finite-difference time-domain (FDTD) method using total-field scattered-field (TFSF) scheme has been performed and validated. PMID:17945575

Trakic, A; Liu, F; Lopez, H S; Wang, H; Crozier, S

2006-01-01

370

Field induced vortex dynamics in magnetic Ni nanotriangles  

Microsoft Academic Search

The magnetization states in Ni triangular dots under an applied magnetic field have been studied using variable-field magnetic force microscopy (VF-MFM) imaging. In order to understand their dynamics we performed micromagnetic simulations which are in remarkable agreement with the experimental MFM results. The nanostructures present magnetic vortices as ground states which move under an external magnetic field. The combination of

M. Jaafar; R. Yanes; A. Asenjo; O. Chubykalo-Fesenko; M. Vázquez; E. M. González; J. L. Vicent

2008-01-01

371

Magnetic-field effects on vacuum insulator flashover  

Microsoft Academic Search

The effect of magnetic fields on dielectric surface breakdown in vacuum and simulated LEO conditions is investigated using pulsed test voltages. Predictions from the saturated secondary electron emission avalanche breakdown model and experimental results both show magnetic insulation effects at magnetic-field amplitudes as low as 0.1 T. The most favorable configuration for magnetic insulation is with the magnetic field oriented

M. Lehr; R. Korzekwa; H. Krompholz; M. Kristiansen

1992-01-01

372

Magnetic Field Maps of Quiescent BOK Globules  

NASA Astrophysics Data System (ADS)

We present magnetic field maps of 12 starless Bok Globules. Maps were constructed from polarimetric V-band images taken with a computer-controlled CCD camera with a fast shutter and a bidirectional charge-shifting capability. The linear polarization of stars in the globule field has been determined by repeated use of imaging through a polaroid filter, shifting the charge up by many times the stellar PSF, reimaging through an orthogonal polaroid filter, then shifting the charge back down to its starting point. Between one and five CCD fields-of-view were necessary to map each globule, and up to 50 stars in each FOV had detectable polarizations. This globule sample exhibits a variety of magnetic field patterns, including uniform fields with dispersion less than 10(deg) , overlapping fields with two distinct directions, and cometary extensions.

Kane, Brian D.; Clemens, Dan P.

1994-12-01

373

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, Å.

2006-05-01

374

Magnetically Insulated Opening Switch Research.  

National Technical Information Service (NTIS)

We examine the feasibility of an opening switch concept based on magnetic insulation in a coaxial thermionic diode. It is found that the impedance ratio between 'closed' and 'open' states of the diode is marginal for efficient energy transfer via this typ...

M. W. McGeoch R. Kraft

1987-01-01

375

High Field Magnet R&D in the USA  

SciTech Connect

Accelerator magnet technology is currently dominated by the use of NbTi superconductor. New and more demanding applications for superconducting accelerator magnets require the use of alternative materials. Several programs in the US are taking advantage of recent improvements in Nb{sub 3}Sn to develop high field magnets for new applications. Highlights and challenges of the US R&D program are presented along with the status of conductor development. In addition, a new R&D focus, the US LHC Accelerator Research Program, will be discussed.

Gourlay, Stephen A.

2003-06-24

376

High Field Magnet R&D in the USA  

SciTech Connect

Accelerator magnet technology is currently dominated by the use of NbTi superconductor. New and more demanding applications for superconducting accelerator magnets require the use of alternative materials. Several programs in the US are taking advantage of recent improvements in Nb{sub 3}Sn to develop high field magnets for new applications. Highlights and challenges of the US R and D program are presented along with the status of conductor development. In addition, a new R and D focus, the US LHC Accelerator Research Program, will be discussed.

Gourlay, S.A.

2003-10-01

377

Cosmic Magnetic Fields: Observations and Prospects  

Microsoft Academic Search

Synchrotron emission, its polarization and its Faraday rotation at radio frequencies of 0.2-10 GHz are powerful tools to study the strength and structure of cosmic magnetic fields. Unpolarized emission traces turbulent fields which are strongest in galactic spiral arms and bars (20-30 muG) and in central starburst regions (50-100 muG). Such fields are dynamically important, e.g. they can drive gas

Rainer Beck

2011-01-01

378

Magnetic Field Structure from Synchrotron Polarization  

Microsoft Academic Search

Total magnetic fields in spiral galaxies, as observed through their total synchrotron emission, are strongest (up to ~=30~muG) in the spiral arms. The degree of radio polarization is low; the field in the arms must be mostly turbulent or tangled. Polarized synchrotron emission shows that the resolved regular fields are generally strongest in the interarm regions (up to ~=15~muG), sometimes

Rainer Beck

2007-01-01

379

Electric/magnetic field sensor  

DOEpatents

A UNLV novel electric/magnetic dot sensor includes a loop of conductor having two ends to the loop, a first end and a second end; the first end of the conductor seamlessly secured to a first conductor within a first sheath; the second end of the conductor seamlessly secured to a second conductor within a second sheath; and the first sheath and the second sheath positioned adjacent each other. The UNLV novel sensor can be made by removing outer layers in a segment of coaxial cable, leaving a continuous link of essentially uncovered conductor between two coaxial cable legs.

Schill, Jr., Robert A. (Henderson, NV); Popek, Marc [Las Vegas, NV

2009-01-27

380

Measurement of Magnetic Fields in Stellar Jets  

NASA Astrophysics Data System (ADS)

This article reviews magnetic field measurements in jets from young stars, focusing on the physics and application of the three main techniques, Zeeman splitting and polarization, gyrosynchrotron radiation, and the analysis of shocked cooling zones. Estimates of field strengths in stellar jets are rare, and do not refer to the axis of the beam close to the source, where knowledge of the field and its geometry is most critical for constraining launching mechanisms of jets. Nevertheless, the existing measurements demonstrate that magnetic fields in YSO jets are strong enough to be important in the dynamics of the cooling zones behind internal shock waves, even though the ram pressure in the bulk flow dominates the magnetic pressure at large distances from the source. Models of pulsed magnetic flow show that velocity perturbations sweep up the field into dense working surfaces within the jet, increasing the relative importance of magnetic pressure to the dynamics in these regions and reducing its importance in the rarefaction regions that lie between the dense knots.

Hartigan, Patrick

381

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

382

Magnetic field stabilization by temperature control of an azimuthally varying field cyclotron magnet  

NASA Astrophysics Data System (ADS)

A magnetic field drift, gradual decrease of the order of 10-4 in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally varying field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of +/-5×10-6 and the beam intensity stability of +/-2% have been achieved by this temperature control.

Okumura, S.; Arakawa, K.; Fukuda, M.; Nakamura, Y.; Yokota, W.; Ishimoto, T.; Kurashima, S.; Ishibori, I.; Nara, T.; Agematsu, T.; Sano, M.; Tachikawa, T.

2005-03-01

383

Magnetic field stabilization by temperature control of an azimuthally varying field cyclotron magnet  

SciTech Connect

A magnetic field drift, gradual decrease of the order of 10{sup -4} in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally varying field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of {+-}5x10{sup -6} and the beam intensity stability of {+-}2% have been achieved by this temperature control.

Okumura, S.; Arakawa, K.; Fukuda, M.; Nakamura, Y.; Yokota, W.; Ishimoto, T.; Kurashima, S.; Ishibori, I.; Nara, T.; Agematsu, T.; Sano, M.; Tachikawa, T. [Japan Atomic Energy Research Institute (JAERI), 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Sumitomo Heavy Industries, Ltd. (SHI), 5-2 Soubiraki, Niihama, Ehime 792-8588 (Japan)

2005-03-01

384

Probing Magnetic Fields with GALFACTS  

NASA Astrophysics Data System (ADS)

GALFACTS is a large-area spectro-polarimetric survey on the Arecibo Radio telescope. It uses the seven-beam focal plane feed array receiver system (ALFA) to carry out an imaging survey project of the 12,700 square degrees of sky visible from Arecibo at 1.4 GHz with 8192 spectral channels over a bandwidth of 300 MHz sampled at 1 millisecond. The aggregate data rate is 875 MB/s. GALFACTS observations will create full-Stokes image cubes at an angular resolution of 3.5' with a band-averaged sensitivity of 90 ?Jy, allowing sensitive imaging of polarized radiation and Faraday Rotation Measure from both diffuse emission and extragalactic sources. GALFACTS is a scientific pathfinder to the SKA in the area of cosmic magnetism. Key to magnetism science with the SKA is the technique of RM synthesis. The technique of RM synthesis is introduced and we discuss practical aspects of RM synthesis including efficient computational techniques and detection thresholds in the resulting Faraday spectrum. We illustrate the use of the technique by presenting the current development of the RM synthesis pipeline for GALFACTS and present early results.

George, S. J.; Stil, J. M.; Andrecut, M.; Taylor, A. R.

2012-09-01

385

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

386

Magnetic fields in merging spirals - the Antennae  

NASA Astrophysics Data System (ADS)

We present an extensive study of magnetic fields in a system of merging galaxies. We obtained for NGC 4038/39 (the Antennae) radio total intensity and polarization maps at 8.44 GHz, 4.86 GHz and 1.49 GHz using the VLA in the C and D configurations. The galaxy pair possesses bright, extended radio emission filling the body of the whole system, with no dominant nuclear sources. The radio thermal fraction of NGC 4038/39 was found to be about 50% at 10.45 GHz, higher than in normal spirals. Most of the thermal emission is associated with star-forming regions, but only a part of these are weakly visible in the optical domain because of strong obscuration. The mean total magnetic fields in both galaxies are about two times stronger (?20 ?G) than in normal spirals. However, the degree of field regularity is rather low, implying tangling of the regular component in regions with interaction-enhanced star formation. Our data combined with those in H I, H?, X-rays and in far infrared allow us to study local interrelations between different gas phases and magnetic fields. We distinguish several radio-emitting regions with different physical properties and at various evolutionary stages: the rudimentary magnetic spiral, the northern cool part of the dark cloud complex extending between the galaxies, its warm southern region, its southernmost star-forming region deficient in radio emission, and the highly polarized northeastern ridge associated with the base of an unfolding tidal tail. The whole region of the dark cloud complex shows a coherent magnetic field structure, probably tracing the line of collision between the arms of merging spirals while the total radio emission reveals hidden star formation nests. The southern region is a particularly intense merger-triggered starburst. Highly tangled magnetic fields reach there strengths of ?30 ?G, even larger than in both individual galaxies, possibly due to compression of the original fields pulled out from the parent disks. In the northeastern ridge, away from star-forming regions, the magnetic field is highly coherent with a strong regular component of 10 ?G tracing gas shearing motions along the tidal tail. We find no signs of field compression by infalling gas there. The radio spectrum is much steeper in this region indicating aging of the CR electron population as they move away from their sources in star-forming regions. Modelling Faraday rotation data shows that we deal with a three-dimensionally curved structure of magnetic fields, becoming almost parallel to the sky plane in the southeastern part of the ridge.

Chy?y, K. T.; Beck, R.

2004-04-01

387

Diquark condensates and the magnetic field of pulsars  

NASA Astrophysics Data System (ADS)

We study the consequences of superconducting quark cores in neutron stars for the magnetic fields of pulsars. We find that within recent nonperturbative approaches to the effective quark interaction the diquark condensate forms a superconductor of second kind whereas previously quark matter was considered as a first kind superconductor. In both cases the magnetic field which is generated in the surrounding hadronic shell of superfluid neutrons and superconducting protons can penetrate into the quark matter core since it is concentrated in proton vortex clusters where the field strength exceeds the critical value. Therefore the magnetic field will not be expelled from the superconducting quark core with the consequence that there is no decay of the magnetic fields of pulsars. Thus we conclude that the occurence of a superconducting quark matter core in pulsars does not contradict the observational data which indicate that magnetic fields of pulsars have life times larger than 10(7) years. Research supported in part by the Volkswagen Stiftung under grant no. I/71 226

Blaschke, D.; Sedrakian, D. M.; Shahabasyan, K. M.

1999-10-01

388

High-field magnetization in transuranium compound  

NASA Astrophysics Data System (ADS)

We measured the high-field magnetization up to 55 T and constructed a magnetic phase diagram for a transuranium antiferromagnet NpRhGa5 with the tetragonal structure. The magnetization at 4.2 K for H?[100] indicates a sharp metamagnetic transition with a step at H=26T and saturates above H=38T, reaching 0.43?/Np. An ordered moment of 0.96?/Np at zero field, which was determined from the neutron scattering experiment, is found to be reduced to 0.43?/Np at H, together with an orientation of the magnetic moment from the (0 0 1) plane to the (1 0 0) plane.

Sugiyama, K.; Nakashima, H.; Aoki, D.; Ikeda, S.; Haga, Y.; Yamamoto, E.; Nakamura, A.; Homma, Y.; Shiokawa, Y.; Kindo, K.; Hagiwara, M.; ?nuki, Y.

2007-03-01

389

Thermal modeling of resistive magnets for field-cycled MRI  

Microsoft Academic Search

In conventional magnetic resonance imaging (MRI), a single superconduct- ing magnet is used during the polarization and signal acquisition phases of imaging. In field-cycled MRI, the superconducting magnet is replaced by two actively controlled resistive magnets: a high-field magnet to polarize the sample and a low-field magnet for signal acquisition. Both resistive magnets generate heat during operation and must be

K. M. Gilbert; W. B. Handler; B. A. Chronik

2005-01-01

390

Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy  

NASA Astrophysics Data System (ADS)

The application of superparamagnetic nanoparticles for in vivo magnetic resonance imaging (MRI) under external ac magnetic field has attracted considerable research efforts in recent years. However, it is unclear how superparamagnetic nanostructures arrange themselves in fluidic environment under external magnetic field. Here, we report direct visualization of the effect of applied magnetic field to the ferrofluids (about 6 nm superparamagnetic magnetite (Fe3O4) nanoparticle ``colloidal'' suspension) using the cryogenic transmission electron microscopy (cryo-TEM). While long dipole chains (up to millimeter range) of the magnetite along the magnetic lines are found in samples dried inside the magnetic field, only short dipole chains (within tens of nanometer scale) with random orientations are observed in the wet sample observed by cryo-TEM. In the wet sample, aggregations of medium-length dipole chains (up to hundreds of nanometer) can be observed at the areas where the nanoparticles are ``solidified'' when phase separation occurs. In situ formation of flux-closure rings is observed at the edge where vitreous ice sublimes due to high-energy electron radiation that leaves magnetite nanoparticles isolated in the vacuum. Such observations may help elucidate the nature of magnetic field-induced assembly in fluidic environment as in the physiological aqueous conditions in MRI and related applications.

Wu, Jinsong; Aslam, M.; Dravid, Vinayak P.

2008-08-01

391

Milestones in the Observations of Cosmic Magnetic Fields  

Microsoft Academic Search

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs, hereafter) of

Jin-Lin Han; Richard Wielebinski

2002-01-01

392

Generation of Density Perturbations by Primordial Magnetic Fields  

Microsoft Academic Search

We study the generation and evolution of density perturbations and peculiar velocities due to primordial magnetic fields. We assume that a random magnetic field was present before recombination and follow the field's effect on the baryon fluid starting at recombination. We find that magnetic fields generate growing density perturbations on length scales larger than the magnetic Jeans length, lambda_B_ and

Eun-Jin Kim; Angela V. Olinto; Robert Rosner

1996-01-01

393

Milestones in the Observations of Cosmic Magnetic Fields  

Microsoft Academic Search

Magnetic fields are observed everywhere in the universe. In this review, we concentrate on the observational aspects of the magnetic fields of Galactic and extragalactic objects. Readers can follow the milestones in the observations of cosmic magnetic fields obtained from the most important tracers of magnetic fields, namely, the star-light polarization, the Zeeman effect, the rotation measures (RMs,hereafter) of extragalactic

Jin-Lin Han; Richard Wielebinski

2002-01-01

394

Magnetic Fields from QCD Phase Transitions  

NASA Astrophysics Data System (ADS)

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 ?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.; Kisslinger, Leonard; Brandenburg, Axel; Kahniashvili, Tina

2012-11-01

395

On quantizing magnetic field effects in low carrier concentration superconductors  

NASA Astrophysics Data System (ADS)

Temperature dependence of the multichannel gap functions within n - th Landau level in s-wave and p-wave superconductors has been calculated. Oscillational magnetic field dependence of the transition temperature and anomalous temperature dependence of gap parameters at critical fields have been obtained. This work is supported by the Committee for Scientific Research (Poland) under grant No. KBN 2 P302 089 04.

Kowalewski, L.; Nogala, M. M.; Thomas, M.; Wojciechowski, R. J.

1994-12-01

396

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

397

Equilibrium magnetization states in magnetic nanotubes and their evolution in external magnetic field  

NASA Astrophysics Data System (ADS)

The equilibrium magnetization states existing in soft magnetic nanotubes and their behavior in external magnetic field are investigated by means of micromagnetic simulation. In the ground state the middle part of a sufficiently long tube is uniformly magnetized along the tube axis, however there are curling states of various circular polarities near the tube ends. The characteristic length of ending curling states, as well as switching field Hs in the external magnetic field parallel to the tube axis, have been calculated as a function of outer tube radius and tube thickness.

Chen, A. P.; Usov, N. A.; Blanco, J. M.; Gonzalez, J.

2007-09-01

398

Diffusive processes in a stochastic magnetic field  

SciTech Connect

The statistical representation of a fluctuating (stochastic) magnetic field configuration is studied in detail. The Eulerian correlation functions of the magnetic field are determined, taking into account all geometrical constraints: these objects form a nondiagonal matrix. The Lagrangian correlations, within the reasonable Corrsin approximation, are reduced to a single scalar function, determined by an integral equation. The mean square perpendicular deviation of a geometrical point moving along a perturbed field line is determined by a nonlinear second-order differential equation. The separation of neighboring field lines in a stochastic magnetic field is studied. We find exponentiation lengths of both signs describing, in particular, a decay (on the average) of any initial anisotropy. The vanishing sum of these exponentiation lengths ensures the existence of an invariant which was overlooked in previous works. Next, the separation of a particle`s trajectory from the magnetic field line to which it was initially attached is studied by a similar method. Here too an initial phase of exponential separation appears. Assuming the existence of a final diffusive phase, anomalous diffusion coefficients are found for both weakly and strongly collisional limits. The latter is identical to the well known Rechester-Rosenbluth coefficient, which is obtained here by a more quantitative (though not entirely deductive) treatment than in earlier works.

Wang, H.; Vlad, M.; Vanden Eijnden, E.; Spineanu, F.; Misguich, J.H.; Balescu, R. [Association Euratom-Etat Belge sur la Fusion, Physique Statistique et Plasmas, Code Postal 231, Universite Libre de Bruxelles, Campus Plaine, Boulevard du Triomphe, 1050 Bruxelles (Belgium)]|[Association Euratom-Commissariat a l`Energie Atomique sur la Fusion, Departement de Recherches sur la Fusion Controle, Centre d`Etudes de Cadarache, 13108 Saint-Paul-lez-Durance Cedex (France)

1995-05-01

399

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

400

Magnetic field measurements of the BLAST spectrometer  

NASA Astrophysics Data System (ADS)

The Bates Large Acceptance Spectrometer Toroid has been built to study nuclear physics reactions using a stored, polarized electron beam and a variety of polarized targets internal to the storage ring. The spectrometer consists of eight coils surrounding the target cell. There is a requirement of nominally zero field along the centerline of the spectrometer for proper electron beam storage. In addition, the polarized internal targets require a low field gradient in the target region. Magnetic field measurements were made near the beam centerline to guide the alignment of the coils and satisfy the field magnitude and gradient requirements. After the coils were aligned, the magnetic field was measured in the detector regions to provide information for particle tracking.

Dow, Karen A.; Botto, Tancredi; Goodhue, Abigail; Hasell, Douglas; Loughnan, Dylan; Murphy, Kilian; Smith, Timothy Paul; Ziskin, Vitaliy

2009-02-01

401

High-field superconducting accelerator magnets  

SciTech Connect

The next generation of accelerators for high-energy physics will require high-field, small-bore dipole magnets: in the region of 10 T and 40-mm diam. For such magnets, there is a great incentive to attain high overall current density through increasing the current density within the superconductor and minimizing the copper stabilizer. Both Nb-Ti operating at 1.8 K and Nb/sub 3/sn at 4.2 are candidate superconductors. Two programs in the US and one in Japan are directed toward the development of such magnets. The program at LBL is described below.

Taylor, C.; Meuser, R.; Caspi, S.; Gilbert, W.; Hassenzahl, W.; Peters, C.; Wolgast, R.

1982-05-01

402

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

403

Fabrication of multipolar magnetic field sources  

NASA Astrophysics Data System (ADS)

The emergence of high-energy-product permanent magnets has made possible the generation of extraordinarily high magnetic fields in the internal working spaces of relatively small structures. The widespread use of such structures has been hampered by the variety and complexity of their magnetic components and the concomitant difficulty and expense of manufacture. This paper describes approaches to fabrication and assembly that should significantly ease both fabricational and economic problems. Examples of these approaches are given for the production of cylindrical multipolar sources (magic rings, quadrupolar electron beam guides) and spherical dipolar sources (magic spheres).

Leupold, H. A.; McLane, G. F.

1994-11-01

404

Magnetic monopoles in field theory and cosmology  

NASA Astrophysics Data System (ADS)

The existence of magnetic monopoles is predicted by many theories of particle physics beyond the Standard Model. However, in spite of extensive searches, there is no experimental or observational sign of them. I review the role of magnetic monopoles in quantum field theory and discuss their implications for particle physics and cosmology. I also highlight their differences and similarities with monopoles found in frustrated magnetic systems, and discuss how experiments carried out in these systems could help us understand the physics of fundamental monopoles.

Rajantie, A.

2012-12-01

405

Firefly flashing under strong static magnetic field.  

PubMed

Firefly flashing has been the subject of numerous scientific investigations. Here we present in vivo flashes from male specimens of three species of fireflies-two Japanese species Luciola cruciata, Luciola lateralis and one Indian species Luciola praeusta-positioned under a superconducting magnet. When the OFF state of the firefly becomes long after flashing in an immobile state under the strong static magnetic field of strength 10 Tesla for a long time, which varies widely from species to species as well as from specimen to specimen, the effect of the field becomes noticeable. The flashes in general are more rapid, and occasionally overlap to produce broad compound flashes. We present the broadest flashes recorded to date, and propose that the strong static magnetic field affects the neural activities of fireflies, especially those in the spent up or 'exhausted' condition. PMID:22131061

Barua, Anurup Gohain; Iwasaka, Masakazu; Miyashita, Yuito; Kurita, Satoru; Owada, Norio

2011-12-01

406

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

407

Consistency relation for cosmic magnetic fields  

NASA Astrophysics Data System (ADS)

If cosmic magnetic fields are indeed produced during inflation, they are likely to be correlated with the scalar metric perturbations that are responsible for the cosmic microwave background anisotropies and large scale structure. Within an archetypical model of inflationary magnetogenesis, we show that there exists a new simple consistency relation for the non-Gaussian cross correlation function of the scalar metric perturbation with two powers of the magnetic field in the squeezed limit where the momentum of the metric perturbation vanishes. We emphasize that such a consistency relation turns out to be extremely useful to test some recent calculations in the literature. Apart from primordial non-Gaussianity induced by the curvature perturbations, such a cross correlation might provide a new observational probe of inflation and can in principle reveal the primordial nature of cosmic magnetic fields.

Jain, Rajeev Kumar; Sloth, Martin S.

2012-12-01

408

Diffusive Shock Acceleration and Magnetic Field Amplification  

NASA Astrophysics Data System (ADS)

Diffusive shock acceleration is the theory of particle acceleration through multiple shock crossings. In order for this process to proceed at a rate that can be reconciled with observations of high-energy electrons in the vicinity of the shock, and for cosmic rays protons to be accelerated to energies up to observed galactic values, significant magnetic field amplification is required. In this review we will discuss various theories on how magnetic field amplification can proceed in the presence of a cosmic ray population. On both short and long length scales, cosmic ray streaming can induce instabilities that act to amplify the magnetic field. Developments in this area that have occurred over the past decade are the main focus of this paper.

Schure, K. M.; Bell, A. R.; O'C Drury, L.; Bykov, A. M.

2012-11-01

409

Euclidean resonance in a magnetic field  

NASA Astrophysics Data System (ADS)

An analogy is found between Wigner resonant tunneling and tunneling across a static potential barrier in a static magnetic field. Whereas in the process of Wigner tunneling an electron encounters a classically allowed region where a discrete energy level coincides with its energy, in the magnetic field the potential barrier is constant in the direction of tunneling. Along the tunneling path, certain regions are formed where, in the classical language, the kinetic energy of the motion perpendicular to tunneling is negative. These regions play the role of potential wells, where a discrete energy level can coincide with the electron energy. This phenomenon, which occurs at a certain magnetic field, is called Euclidean resonance and substantially depends on the shape of the potential forces in the direction perpendicular to tunneling. Under conditions of Euclidean resonance, a long-distance underbarrier motion is possible, which can be observed in experiments.

Ivlev, B.

2007-08-01

410

Magnetic field propagation in a stellar dynamo  

NASA Astrophysics Data System (ADS)

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from the solar butterfly diagram. When simulated at the base of the convection zone, the fields propagate in the right direction at roughly the right speed. However, owing to the numerical difficulty, a full magnetic cycle has not been simulated in this region. As a result, it is still uncertain where and how the solar dynamo operates.

Glatzmaier, Gary A.

1985-06-01

411

Magnetic Fields of the Outer Planets  

NASA Astrophysics Data System (ADS)

The rapidly rotating giant planets of the outer solar system all possess strong dynamo-driven magnetic fields that carve a large cavity in the flowing magnetized solar wind. Each planet brings a unique facet to the study of planetary magnetism. Jupiter possesses the largest planetary magnetic moment, 1.55×1020 Tm3, 2×104 times larger than the terrestrial magnetic moment whose axis of symmetry is offset about 10° from the rotation axis, a tilt angle very similar to that of the Earth. Saturn has a dipole magnetic moment of 4.6×1018 Tm3 or 600 times that of the Earth, but unlike the Earth and Jupiter, the tilt of this magnetic moment is less than 1° to the rotation axis. The other two gas giants, Uranus and Neptune, have unusual magnetic fields as well, not only because of their tilts but also because of the harmonic content of their internal fields. Uranus has two anomalous tilts, of its rotation axis and of its dipole axis. Unlike the other planets, the rotation axis of Uranus is tilted 97.5° to the normal to its orbital plane. Its magnetic dipole moment of 3.9×1017 Tm3 is about 50 times the terrestrial moment with a tilt angle of close to 60° to the rotation axis of the planet. In contrast, Neptune with a more normal obliquity has a magnetic moment of 2.2×1017 Tm3 or slightly over 25 times the terrestrial moment. The tilt angle of this moment is 47°, smaller than that of Uranus but much larger than those of the Earth, Jupiter and Saturn. These two planets have such high harmonic content in their fields that the single flyby of Voyager was unable to resolve the higher degree coefficients accurately. The four gas giants have no apparent surface features that reflect the motion of the deep interior, so the magnetic field has been used to attempt to provide this information. This approach works very well at Jupiter where there is a significant tilt of the dipole and a long baseline of magnetic field measurements (Pioneer 10 to Galileo). The rotation rate is 870.536° per day corresponding to a (System III) period of 9 h 55 min 26.704 s. At Saturn, it has been much more difficult to determine the equivalent rotation period. The most probable rotation period of the interior is close to 10 h 33 min, but at this writing, the number is still uncertain. For Uranus and Neptune, the magnetic field is better suited for the determination of the planetary rotation period but the baseline is too short. While it is possible that the smaller planetary bodies of the outer solar system, too, have magnetic fields or once had, but the current missions to Vesta, Ceres and Pluto do not include magnetic measurements.

Russell, C. T.; Dougherty, M. K.

2010-05-01

412

Fabrication of cables for the background-field magnet system of SSTF  

Microsoft Academic Search

The Korea Superconducting Tokamak Advanced Research (KSTAR) device has a fully superconducting magnet system consisting of 16 Toroidal Field (TF) and 14 Poloidal Field (PF) coils. For the test of the KSTAR cable-in-conduit conductor (CICC), an ambient magnetic field of ±8 T with a maximum change rate of 20 T\\/s is required and a background-field magnet system is being developed

S. Lee; B. Lim; S. Baang; M. Kim; J. Kim; I. Han; B. Lee; K. Kim

2002-01-01

413

Electric Field Measurement for HPM Research.  

National Technical Information Service (NTIS)

In this report, a description is given of the electric field measurement system at FOI Grids Jon Research Centre for HPM research. The system is intended for measurement of the electric field components in electromagnetic waves in the gigahertz region.

P. Appelgren T. Hultman A. Larsson

2003-01-01

414

The symmetry properties of planetary magnetic fields  

SciTech Connect

This paper provides a comparative study of the geometrical structures of the magnetic fields of Earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For Earth, Jupiter, and Saturn the centered dipole, quadrupole, and octupole contributions are included, while at Uranus, only the dipole and quadrupole contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. It is found that there are a number of common features of the magnetic fields of Earth and Jupiter. Compared to Earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis, by now rather well known, but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

Raedler, K.H. (Zentral Inst. fuer Astrophysik, Potsdam-Babelsberg (East Germany)); Ness, N.F. (Univ. of Delaware, Newark (United States))

1990-03-01

415

Steady State Chaotic Magnetic Fields and Particle Dynamics Cross-field Transport of Particles in Chaotic Magnetic Fields  

Microsoft Academic Search

The observed propagation of cosmic rays in the interplanetary space cannot be explained unless there is diffusion of the energetic particles across the interplanetary magnetic field. The cross-field diffusion of cosmic rays is assumed to be due to the chaotic nature of the interplanetary\\/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and

B. Dasgupta; A. Ram

2009-01-01

416

Solar atmospheric rotation and the magnetic field  

NASA Astrophysics Data System (ADS)

Solar rotation is known for more than four centuries, yet it is still an unresolved issue of solar physics. The rotation has been measured by three methods e.g. Feature tracing, Spectroscopic and flux modulation. We have used the last quite extensively for the estimation of rotation of the solar outer atmosphere, namely chromosphere and corona. These studies used Radio, X-ray and EUV images of the Sun. These investigations have provided quite detailed and systematic information of the solar rotation and its variability. This has established that solar atmosphere has differential rotation and the differentiality has a significant temporal and spatial variability. The spatial variability show that there is North-South asymmetry in the rotation of solar atmosphere. This asymmetry changes sign every solar cycle. This may be related to "Hale cycle". In this paper we tried to combine the Radio, X-ray and EUV estimates of rotation by comparative interpolation. The combined rotation profiles are drawn in the space-time coordinate in the same format as the longitudinal averaged magnetic field. The average magnetic field shows beautiful butterfly structures and poleward flow of the magnetic fields of opposite polarity. Preliminary comparison show that asymmetric differential rotation of the solar atmosphere peaks when the magnetic filed structure is more complex. In this paper a detail comparison of the magnetic field and solar atmospheric rotation will presented.

Chandra, Satish; Vats, Hari

2012-07-01

417

Galactic dynamics and magnetic fields. 2: Magnetic fields in barred galaxies  

NASA Astrophysics Data System (ADS)

We present a magnetic-field amplification process in galaxies in conjunction with bar dynamics. Our model considers especially the observed non-circular gas velocities in barred spiral galaxies. The bar drives the spirally-falling gas flow toward the center, which consists of a net radial flow (referred to as flow b) and an elliptically elongated flow rotating in the azimuth (flow a). The induced radial flow by a bar (flow b) produces a magnetic field, whose exponential growth is closely related with the angular-momentum transport by the non-axisymmetric bar perturbation. Furthermore, the non-axisymmetric gas flow (flow a) also leads to the exponential and oscillatory growth of magnetic fields by driving a growing magnetic wave. The interplay of both flows in a bar hence induces an oscillatory amplification of magnetic fields, and the resulting magnetic field pattern rotates with a bar and holds the azimuthal wavenumber m = 1 or 2, depending on the strength of velocity disturbances. This model naturally explains the characteristic radio features observed in M83, where the m = 1 magnetic field is aligned with the bar, and the bar ends are dominated by the vertical component Bz, giving the holes in polarized intensity map. It is emphasized that the evolution of galactic magnetic fields is closely related with galactic dynamics and evolution.

Chiba, M.; Lesch, H.

1994-04-01

418

Permanent Magnet Spiral Motor for Magnetic Gradient Energy Utilization: Axial Magnetic Field  

NASA Astrophysics Data System (ADS)

The Spiral Magnetic Motor, which can accelerate a magnetized rotor through 90% of its cycle with only permanent magnets, was an energy milestone for the 20th century patents by Kure Tekkosho in the 1970's. However, the Japanese company used old ferrite magnets which are relatively weak and an electrically-powered coil to jump start every cycle, which defeated the primary benefit of the permanent magnet motor design. The principle of applying an inhomogeneous, anisotropic magnetic field gradient force Fz = ? cos J dB/dz, with permanent magnets is well-known in physics, e.g., Stern-Gerlach experiment, which exploits the interaction of a magnetic moment with the aligned electron spins of magnetic domains. In this case, it is applied to dB/d? in polar coordinates, where the force F? depends equally on the magnetic moment, the cosine of the angle between the magnetic moment and the field gradient. The radial magnetic field increases in strength (in the attractive mode) or decreases in strength (in the repulsive mode) as the rotor turns through one complete cycle. An electromagnetic pulsed switching has been historically used to help the rotor traverse the gap (detent) between the end of the magnetic stator arc and the beginning (Kure Tekko, 1980). However, alternative magnetic pulse and switching designs have been developed, as well as strategic eddy current creation. This work focuses on the switching mechanism, novel magnetic pulse methods and advantageous angular momentum improvements. For example, a collaborative effort has begun with Toshiyuki Ueno (University of Tokyo) who has invented an extremely low power, combination magnetostrictive-piezoelectric (MS-PZT) device for generating low frequency magnetic fields and consumes ``zero power'' for static magnetic field production (Ueno, 2004 and 2007a). Utilizing a pickup coil such as an ultra-miniature millihenry inductor with a piezoelectric actuator or simply Wiegand wire geometry, it is shown that the necessary power for magnetic field switching device can be achieved in order to deflect the rotor magnet in transit. The Wiegand effect itself (bistable FeCoV wire called ``Vicalloy'') invented by John Wiegand (Switchable Magnetic Device, US Patent No.4,247,601), utilizing Barkhausen jumps of magnetic domains, is also applied for a similar achievement (Dilatush, 1977). Conventional approaches for spiral magnetic gradient force production have not been adequate for magnetostatic motors to perform useful work. It is proposed that integrating a magnetic force control device with a spiral stator inhomogeneous axial magnetic field motor is a viable approach to add a sufficient nonlinear boundary shift to apply the angular momentum and potential energy gained in 315 degrees of the motor cycle.

Valone, Thomas F.

2010-01-01

419

Field-line transport in stochastic magnetic fields: Percolation, Lévy flights, and non-Gaussian dynamics  

Microsoft Academic Search

The transport of magnetic field lines is studied numerically in the case where strong three-dimensional magnetic fluctuations are superimposed to a uniform average magnetic field. The magnetic percolation of field lines between magnetic islands is found, as well as a non-Gaussian regime where the field lines exhibit Lévy random walks, changing from Lévy flights to trapped motion. Anomalous diffusion laws

G. Zimbardo; P. Veltri

1995-01-01

420

Magnetism of filled skutterudites under high magnetic fields  

NASA Astrophysics Data System (ADS)

We measured the high-field magnetization M for skutterudite compounds of a paramagnet PrFe4Sb12 and a ferromagnet SmOs4Sb12 to investigate the characteristic magnetic properties. In PrFe4Sb12, we observed a peak structure in the dM/dH curve, which might be a level crossing effect between the singlet ground state and the excited state with a splitting energy of about 20 K in the crystalline electric field (CEF) scheme. In SmOs4Sb12, the anisotropy of magnetization for H?[100] and [1 1 0] was not observed, which is inconsistent with the quartet ground state in the CEF scheme.

Yamada, T.; Nakashima, H.; Sugiyama, K.; Hagiwara, M.; Kindo, K.; Tanaka, K.; Kikuchi, D.; Aoki, Y.; Sugawara, H.; Sato, H.; Settai, R.; ?nuki, Y.; Harima, H.

2007-03-01

421

Regional And Global Evolution Of Mars: Insights From Geologic, Topographic, and Magnetic Field Observations  

NASA Astrophysics Data System (ADS)

Johnson and Phillips (2005) used magnetic field observations from Mars Global Surveyor (MGS), the ages of geologic units, and topographic data to provide constraints on the thermal and magmatic evolution of the Tharsis volcanic province on Mars. They conclude that Tharsis is underlain by a Noachian crust that was previously more magnetic than at present. Here, we extend these analyses to other regions and to the entire planet. We investigate the distributions of magnetic field intensities and directions (or the inferred magnetizations) as a function of geological age, where the latter is assessed via global maps of surface unit ages. Available global geological maps have higher spatial resolution (0.125°) compared with global magnetic field models ( 2° at best). The geologic data are grouped into bins of the same size as the magnetic field data and a modal age is assigned to the bin. The number of magnetic observations (magnetic field or magnetization), the mean value, standard deviation, and maximum values are computed for each bin. We test whether magnetic anomaly and/or inferred magnetization distributions are consistent with an ancient global dipolar magnetizing field. Geologic age data provide constraints on the timing of events that may have magnetized or subsequently modified the crust. Topographic data provide information related to processes that affect topography, such as uplifting. Analyses of the combined magnetic field, geologic age, and topographic data, will help to constrain regional and global models of Martian evolution. This research is supported in part by a NASA Graduate Student Research Program fellowship.

Milbury, Colleen A.; Johnson, C. L.; Schubert, G.

2006-09-01

422

Vortex-like magnetization of multilayer magnetic nanoisland systems in weak magnetic fields  

NASA Astrophysics Data System (ADS)

The results of studies of magnetization processes of multilayer structures, consisting of periodically alternating island layers of various magnetic materials, are presented. The unidirectional axis of magnetization, which does not lead to exchange bias of hysteresis loops, is found in these structures. A vortex-like type of magnetization of island structures, when the vortex magnetization is distributed on set of nanoislands, is proposed. Preliminary simulations and experiments on the effects of vortex magnetic field on island systems have shown that proposed vortex-like state can be implemented in multilayer island systems and can influence their magnetic structure.

Boltaev, A. P.; Pudonin, F. A.; Sherstnev, I. A.

2013-04-01

423

Simplified evaluation of magnetic field fluctuation thermometry  

NASA Astrophysics Data System (ADS)

Recently, a Bayesian approach has been proposed for evaluating magnetic field fluctuation thermometry measurements. The approach provides a coherent use of calibration results in the inference of the temperature from subsequent magnetic field fluctuation thermometry measurements. It does, however, rely on an extensive numerical effort. In this paper, we develop simplified parametric and non-parametric analysis schemes. For all approaches we derive analytic expressions for the resulting temperature estimates and their uncertainties. We assess the new approaches and show in particular that an easy to apply non-parametric analysis yields results which are in good agreement with those obtained by the Bayesian inference.

Wübbeler, G.; Elster, C.

2013-11-01

424

Far field subwavelength imaging of magnetic patterns  

NASA Astrophysics Data System (ADS)

Far field imaging of subwavelength magnetic objects in real time is a very challenging issue. We propose an original solution based on a planar array of closely spaced split ring resonators. Hybridization between the resonators of such metalens induces subwavelength modes with different frequencies. Thanks to these high Q resonating modes, Purcell like effect allows an evanescent source, close to the metalens, to emit waves that can be collected efficiently in the far field. We present the first microwave experimental demonstration of such metalens to image of a subwavelength magnetic pattern. Numerical simulation shows that this approach is still valid at THz frequencies.

Ourir, Abdelwaheb; Lerosey, Geoffroy; Lemoult, Fabrice; Fink, Mathias; de Rosny, Julien

2012-09-01

425

Neutrino conversions in solar random magnetic fields  

NASA Astrophysics Data System (ADS)

We consider the effect of a random magnetic field in the convective zone of the Sun superimposed to a regular magnetic field on resonant neutrino spin-flavor oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ a model motivated regular magnetic field profile: it is a static field solution to the solar equilibrium hydro-magnetic equations. These solutions have been known for a long time in the literature. We show for the first time that in addition they are twisting solutions. In this scenario electron antineutrinos are produced through cascades like ?eL-->??L-- >?~eR, The detection of ?~eR at Earth would be a long-awaited signature of the Majorana nature of the neutrino. The expected signals in the different experiments (SK, GALLEX-SAGE, Homestake) are obtained as a function of the level of noise, regular magnetic field and neutrino mixing parameters. Previous results obtained for small mixing and ad-hoc regular magnetic profiles are reobtained. We confirm the strong suppression for a large part of the parameter space of the ?~eR-flux for high energy boron neutrinos in agreement with present data of the SK experiment. We find that MSW (Mikheyev-Smirnov-Wolfenstein) regions (?m2~=10-5 eV2, both small and large mixing solutions) are stable up to very large levels of noise (P=0.7-0.8) but they are acceptable from the point of view of antineutrino production only for moderate levels of noise (P~=0.95). For strong noise and a reasonable regular magnetic field, any parameter region (?m2, sin 2 2?) is excluded. As a consequence, we are allowed to reverse the problem and to put limits on the r.m.s. field strength and transition magnetic moments by demanding a particle physics solution to the SNP in this scenario.

Semikoz, V. B.; Torrente-Lujan, E.

1999-09-01

426

Reconnection rates of magnetic fields  

SciTech Connect

The Sweet-Parker and Petschek scalings of magnetic reconnection rate are modified to include the effect of the viscosity. The modified scalings show that the viscous effect can be important in high-..beta.. plasmas. The theoretical reconnection scalings are compared with numerical simulation results in a tokamak geometry for three different cases: a forced reconnection driven by external coils, the nonlinear m = 1 resistive internal kink, and the nonlinear m = 2 tearing mode. In the first two cases, the numerical reconnection rate agrees well with the modified Sweet-Parker scaling, when the viscosity is sufficiently large. When the viscosity is negligible, a steady state which was assumed in the derivation of the reconnection scalings is not reached and the current sheet in the reconnection layer either remains stable through sloshing motions of the plasma or breaks up to higher m modes. When the current sheet remains stable, a rough comparison with the Sweet-Parker scaling is obtained. In the nonlinear m = 2 tearing mode case where the instability is purely resistive, the reconnection occurs on the slower dissipation time scale (Psi/sub s/ approx. eta). In addition, experimental data of the nonlinear m = 1 resistive internal kink in tokamak discharges are analyzed and are found to give reasonable agreement with the modified Sweet-Parker scaling.

Park, W.; Monticello, D.A.; White, R.B.

1983-05-01

427

Induced Magnetic Fields in Solar System Bodies  

NASA Astrophysics Data System (ADS)

Electromagnetic induction is a powerful technique to study the electrical conductivity of the interior of the Earth and other solar system bodies. Information about the electrical conductivity structure can provide strong constraints on the associated internal composition of planetary bodies. Here we give a review of the basic principles of the electromagnetic induction technique and discuss its application to various bodies of our solar system. We also show that the plasma environment, in which the bodies are embedded, generates in addition to the induced magnetic fields competing plasma magnetic fields. These fields need to be treated appropriately to reliably interpret magnetic field measurements in the vicinity of solar system bodies. Induction measurements are particularly important in the search for liquid water outside of Earth. Magnetic field measurements by the Galileo spacecraft provide strong evidence for a subsurface ocean on Europa and Callisto. The induction technique will provide additional important constraints on the possible subsurface water, when used on future Europa and Ganymede orbiters. It can also be applied to probe Enceladus and Titan with Cassini and future spacecraft.

Saur, Joachim; Neubauer, Fritz M.; Glassmeier, Karl-Heinz

2010-05-01

428

New electric field in asymmetric magnetic reconnection.  

PubMed

We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site. PMID:24116786

Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

2013-09-23

429

Three-dimensional coupled-fields analysis of high-current vacuum arcs with an axial magnetic field  

Microsoft Academic Search

The capabilities and advantages of vacuum interrupters have been widely recognized on switching and controlling the fault currents in medium voltage level, and there have been doing various research and developments for using vacuum interrupters in transmission and distribution lines due to its environmental friendliness. Axial magnetic field electrodes are widely used in vacuum interrupters because the axial magnetic field

J. C. Lee; Y. J. Kim

2010-01-01

430

Complex magnetic fields in an active region  

NASA Astrophysics Data System (ADS)

High-resolution observations of the full Stokes vector in Fe\\sc i spectral lines around 5250 Angstroms obtained at the Swedish Vacuum Solar Telescope on La Palma with the ZIMPOL I Stokes polarimeter in a complex active region reveal the presence of anomalously shaped Stokes profiles indicating the coexistence of at least two magnetic components within the same spatial resolution element. These Stokes profiles have been analyzed with an inversion code based on a 3-component atmospheric model with two magnetic and one field-free component. The fits to the observations in a magnetic region that resembles a small penumbra reveal the presence of a horizontal magnetic field component with an average field strength of /line{B}=840 G, a mean filling factor of /line?=0.12, and an average temperature /line{T}=5400 K at log {tau_ {5000}}=-1.5 embedded in the main ``penumbral'' magnetic field that has /line{B}=1500 G, /line?=0.56, and /line{T}=4900 K. The horizontal component exhibits a mean outflow of 2.7 km s(-1) which is mainly due to the Evershed flow. In a region where there are strong downflows up to 7 km s(-1) , we infer the possible presence of a shock front whose height changes along the slit. The height variation can be explained by a change of the gas pressure at the base of the photosphere below the shock front as proposed by Thomas & Montesinos (1991). Small plages with field strengths below 900 G have been observed in the vicinity of some pores. Finally, we present a puzzling field structure at the boundary between two adjacent pores. Ambiguous results suggest that although the inversion code is able to successfully invert even very complex Stokes profiles, we are far from a complete description of the field structure in complex magnetic regions. We warn that magnetograms and fits to data involving only a single magnetic component may hide the true complexity of the magnetic structure in at least some parts of active regions.

Bernasconi, P. N.; Keller, C. U.; Solanki, S. K.; Stenflo, J. O.

1998-01-01

431

Variable field magnetic extraction channel for ORIC  

SciTech Connect

An improved magnetic beam extraction channel for the Oak Ridge Isochronous Cyclotron (ORIC) has been designed to significantly reduce the external field disturbance and provide uniform in-channel field. This will make beam extraction near nu/sub r/ = 1 more predictable. The new channel consists of an iron tube of constant cross section with independently adjustable windings, both inside and outside the iron. The windings have a cos theta current density distribution. The iron tube is 1 meter long with a bore of 6 cm; aperture for beam is 4 cm. The external field is negligible except for small perturbations in the field arising from the geometry modifications required at the ends so that the beam can enter and leave. The field reduction inside the channel is variable from 0.4 to 0.6 Tesla without significant change in either the internal field uniformity or the external field level. 4 refs., 8 figs., 1 tab.

Hudson, E.D.; Martin, J.A.; Lord, R.S.

1985-01-01

432

The French High Magnetic Field Facility  

NASA Astrophysics Data System (ADS)

The Laboratoire National des Champs Magnétiques Intenses (LNCMI) is a host laboratory for experiments in high magnetic fields. It was created on the 1st of January 2009 through the merger of the Laboratoire des Champs Magnetiques Intenses (Grenoble, specialized in DC fields) and the Laboratoire National des Champs Magnétiques Pulsés (Toulouse, specialized in pulsed fields). The facility is open to a large community of users from all over Europe and the rest of the world. In this paper we report our efforts to offer the highest magnetic fields, ranging from 35 T DC, through 80 T non-destructive, up to 170 T semi-destructive, in the best conditions for our in-house and visiting scientists. We describe the installations and coils improvements. As an example of our activity we present some recent scientific results.

Béard, J.; Debray, F.

2013-03-01

433

Magnetism  

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.

Team, University C.

2007-12-12

434

Terrestrial magnetic field effects on large photomultipliers  

NASA Astrophysics Data System (ADS)

The effects of the Earth's magnetic field on the performance of large PMTs for a cubic-kilometer-scale neutrino telescope has been studied. Measurements were performed for three Hamamatsu PMTs: two 8? R5912 types; one with a standard and the other with a super bialkali photocathode, and a 10? R7081 type with a standard bialkali photocathode. The main characteristics of the PMTs, such as detection efficiency, transit time, transit time spread, gain, peak-to-valley ratio, charge resolution and fractions of spurious pulses were measured while varying the PMT orientations with respect to the Earth's magnetic field. The measurements were performed both with and without a mu-metal cage magnetic shielding. For the 8? PMTs the impact of the magnetic field was found to be smaller than for the 10? PMT. The magnetic shielding strongly reduced the orientation-dependent variations measured for the 10? PMT and even improved the performance. Although less pronounced, improvements were also measured for the 8? PMTs.

on behalf of the KM3NeT Consortium; Leonora, E.

2013-10-01

435

Development of an Alterable and Rotary Permanent Magnetic Field  

Microsoft Academic Search

In this paper, a system that can produce alterable and rotary permanent magnetic field is developed. It can be used for crystal growth, chemical crystal and biologic cell, etc. A homogeneous magnetic field can be produced in the central region by two annular permanent magnets, and the density of magnetic flux is controlled by changing the angle of the magnetic

Qingxin Yang; Fugui Liu; Zhigang Zhao; Duyan Geng; Shunxin Zhang; Weili Yan

2010-01-01

436

Correlated electrons in an external magnetic field  

NASA Astrophysics Data System (ADS)

Increasing external magnetic field B gradually forces the electron spins to align in the direction of the applied field. The Hartree solution becomes exact for B>=Bs(U). A new small parameter ?B=Bs-B enables one to control the transition between weak- and strong-coupling regimes and the metal-insulator transition. Necessity for dynamical vertex corrections at intermediate and strong coupling is demonstrated.

Janiš , V.

1999-01-01

437

Magnetic field influence on paramecium motility  

SciTech Connect

The influence of a moderately intense static magnetic field on movement patterns of free swimming Paramecium was studied. When exposed to fields of 0.126 T, these ciliated protozoa exhibited significant reduction in velocity as well as a disorganization of movement pattern. It is suggested that these findings may be explained on the basis of alteration in function of ion specific channels within the cell membrane.

Rosen, M.F.; Rosen, A.D. (State Univ. of New York, Stony Brook (USA))

1990-01-01

438

Synthetic magnetic fields for ultracold neutral atoms.  

PubMed

Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation-a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall effect in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, which is evident from the appearance of vortices in our Bose-Einstein condensate. Our approach uses a spatially dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems. With a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation. PMID:19956256

Lin, Y-J; Compton, R L; Jiménez-García, K; Porto, J V; Spielman, I B

2009-12-01

439

Three-Dimensional Magnetic Field Line Reconnection involving Magnetic Flux Ropes (Invited)  

Microsoft Academic Search

We report on two experiments in which three dimensional magnetic field line reconnection plays a role. Magnetic field line reconnection is a processes in which the magnetic field energy is converted to particle energy and heating accompanied by changes in the magnetic topology. In the first experiment two magnetic flux ropes are generated from initially adjacent pulsed current channels in

W. N. Gekelman; B. van Compernolle; E. Lawrence; S. T. Vincena

2010-01-01

440

Magnetic Marker Monitoring Using a Permanent Magnetic Sphere Oriented by a Rotating Magnetic Field  

Microsoft Academic Search

Magnetic marker monitoring (MMM) is a diagnostic technique known since about 1990 and mainly applied for motility assessment in the digestive tract. A particularly favorable MMM method uses a rotating marker, which can be aligned along an externally applied magnetic field HP. This novel method of rotating magnetic marker monitoring (RMMM) provides the starting point for the construction of small

W. Andrä; M. E. Bellemann; M. Brand; J. Haueisen; H. Lausch; P. Saupe; C. Werner

441

Laboratory Measurements of Astrophysical Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

442

Magnetic fields and density functional theory  

SciTech Connect

A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

Salsbury Jr., Freddie

1999-02-01

443

Center for Magnetic Recording Research (CMRR)  

NSDL National Science Digital Library

The Center for Magnetic Recording Research (CMRR) was established to advance the state-of-the-art in magnetic storage, and to produce highly trained graduate students and postdoctoral professionals. CMRR also serves as a catalyst for joint investigations amongst its industrial sponsors, government agencies, and the university. The Center is on the campus of the University of California, San Diego and includes an onsite library.

444

Magnetic isotope and magnetic field effects on the silicon oxidation  

NASA Astrophysics Data System (ADS)

Silicon oxidation by oxygen depends on the magnetic field and exhibits isotope effect: silicon atoms 29Si with magnetic nuclei are oxidized twice as fast as atoms 28Si and 30Si with nonmagnetic nuclei. Both effects certify that the oxidation is a spin selective reaction in which radical pairs participate. The dominating oxidizing species are oxygen molecules in triplet spin state which generate triplet radical pairs. Zeeman interaction and hyperfine coupling with 29Si nuclei in these pairs stimulate triplet-singlet spin conversion and transform triplet pairs into the reactive singlet ones. The subsequent spin allowed reactions in the latter result in the oxidation products.

Koplak, Oksana; Morgunov, Roman; Buchachenko, Anatoly

2013-02-01