Magnetic vector field tag and seal
Johnston, Roger G.; Garcia, Anthony R.
2004-08-31
One or more magnets are placed in a container (preferably on objects inside the container) and the magnetic field strength and vector direction are measured with a magnetometer from at least one location near the container to provide the container with a magnetic vector field tag and seal. The location(s) of the magnetometer relative to the container are also noted. If the position of any magnet inside the container changes, then the measured vector fields at the these locations also change, indicating that the tag has been removed, the seal has broken, and therefore that the container and objects inside may have been tampered with. A hollow wheel with magnets inside may also provide a similar magnetic vector field tag and seal. As the wheel turns, the magnets tumble randomly inside, removing the tag and breaking the seal.
Inclination angle of vector magnetic fields.
NASA Astrophysics Data System (ADS)
Yanping, Lü; Wang, Jingxiu
1994-11-01
The authors further elaborate on an empirical method to improve the consistency of the line-of-sight and transverse field calibration. The method can also be used to check the transverse field calibration. Furthermore, based on the correction, the authors calculate the inclination angle of the vector magnetic field related to the solar surface, which can give some information on how the vector magnetic field is distributed in space.
Mapping the magnetic field vector in a fountain clock
Gertsvolf, Marina; Marmet, Louis [National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)
2011-12-15
We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.
Vector magnetic field camera for permanent magnets inspection
NASA Astrophysics Data System (ADS)
Chady, T.; Psuj, G.; Todaka, T.; Enokizono, M.
2013-01-01
Permanent magnets are widely used in many applications. A fast and reliable system for online evaluation of permanent magnets is required for their quality assurance. Therefore, a new measurement system has been developed to measure the spatial distribution of the vector magnetic field. The system consists of a complex Hall transducer, an analog multiplexer, a mechanical XYZ scanner and a control computer. The matrix of Hall sensors is designed in this way that all 3 components can be measured at once in multiple points. Such kind of transducer enables to reduce the time needed for inspection. The similar matrix transducer was also utilized to evaluate state of magnetized ferromagnetic materials.
Several problems in measuring solar vector magnetic fields
NASA Astrophysics Data System (ADS)
Su, J. T.; Zhang, H. Q.; Ruan, G. P.; Sun, Y. Z.
Observations of solar photosphere vector magnetic fields with a magnetograph are subjected to many difficulties, such as azimuth ambiguity, magnetic saturation, Faraday rotation, scattered light, polarization crosstalk, and wavelength shift, and so on. Among these issues, Faraday rotation and scattered light are obvious in local-region vector magnetic field measurements with the 35 cm Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observing Station (HSOS), while polarization crosstalk and wavelength shift are obvious in full-disk vector magnetic field measurements made with a new-developed telescope named Solar Magnetism and Activity Telescope (SMAT). In this paper we put emphasis on these four issues to show how they could affect the measurement accuracy of solar vector magnetic fields. Some preliminary attempts are also made to overcome them.
Inferring Lower Boundary Driving Conditions Using Vector Magnetic Field Observations
NASA Technical Reports Server (NTRS)
Schuck, Peter W.; Linton, Mark; Leake, James; MacNeice, Peter; Allred, Joel
2012-01-01
Low-beta coronal MHD simulations of realistic CME events require the detailed specification of the magnetic fields, velocities, densities, temperatures, etc., in the low corona. Presently, the most accurate estimates of solar vector magnetic fields are made in the high-beta photosphere. Several techniques have been developed that provide accurate estimates of the associated photospheric plasma velocities such as the Differential Affine Velocity Estimator for Vector Magnetograms and the Poloidal/Toroidal Decomposition. Nominally, these velocities are consistent with the evolution of the radial magnetic field. To evolve the tangential magnetic field radial gradients must be specified. In addition to estimating the photospheric vector magnetic and velocity fields, a further challenge involves incorporating these fields into an MHD simulation. The simulation boundary must be driven, consistent with the numerical boundary equations, with the goal of accurately reproducing the observed magnetic fields and estimated velocities at some height within the simulation. Even if this goal is achieved, many unanswered questions remain. How can the photospheric magnetic fields and velocities be propagated to the low corona through the transition region? At what cadence must we observe the photosphere to realistically simulate the corona? How do we model the magnetic fields and plasma velocities in the quiet Sun? How sensitive are the solutions to other unknowns that must be specified, such as the global solar magnetic field, and the photospheric temperature and density?
Deriving Potential Coronal Magnetic Fields from Vector Magnetograms
Welsch, Brian T
2015-01-01
The minimum-energy configuration for the magnetic field above the solar photosphere is curl-free (hence, by Ampere's law, also current-free), so can be represented as the gradient of a scalar potential. Since magnetic fields are divergence free, this scalar potential obeys Laplace's equation, given an appropriate boundary condition (BC). With measurements of the full magnetic vector at the photosphere, it is possible to employ either Neumann or Dirichlet BCs there. Historically, the Neumann BC was used, since available line-of-sight magnetic field measurements approximated the radial field needed for the Neumann BC. Since each BC fully determines the 3D vector magnetic field, either choice will, in general, be inconsistent with some aspect of the observed field on the boundary, due to the presence of both currents and noise in the observed field. We present a method to combine solutions from both Dirichlet and Neumann BCs to determine a hybrid potential field that minimizes the integrated square of the residu...
Determination of Coronal Magnetic Fields from Vector Magnetograms
NASA Technical Reports Server (NTRS)
Mikic, Zoran
1997-01-01
During the course of the present contract we developed an 'evolutionary technique' for the determination of force-free coronal magnetic fields from vector magnetograph observations. The method can successfully generate nonlinear force- free fields (with non-constant-a) that match vector magnetograms. We demonstrated that it is possible to determine coronal magnetic fields from photospheric measurements, and we applied it to vector magnetograms of active regions. We have also studied theoretical models of coronal fields that lead to disruptions. Specifically, we have demonstrated that the determination of force-free fields from exact boundary data is a well-posed mathematical problem, by verifying that the computed coronal field agrees with an analytic force-free field when boundary data for the analytic field are used; demonstrated that it is possible to determine active-region coronal magnetic fields from photospheric measurements, by computing the coronal field above active region 5747 on 20 October 1989, AR6919 on 15 November 1991, and AR7260 on 18 August 1992, from data taken with the Stokes Polarimeter at Mees Solar Observatory, University of Hawaii; started to analyze active region 7201 on 19 June 1992 using measurements made with the Advanced Stokes Polarimeter at NSO/Sac Peak; investigated the effects of imperfections in the photospheric data on the computed coronal magnetic field; documented the coronal field structure of AR5747 and compared it to the morphology of footpoint emission in a flare, showing that the 'high- pressure' H-alpha footpoints are connected by coronal field lines; shown that the variation of magnetic field strength along current-carrying field lines is significantly different from the variation in a potential field, and that the resulting near-constant area of elementary flux tubes is consistent with observations; begun to develop realistic models of coronal fields which can be used to study flare trigger mechanisms; demonstrated that magnetic nonequilibrium can disrupt sheared coronal arcades, and that helmet streamers can disrupt, leading to coronal mass ejections. Our model has significantly extended the realism with which the coronal magnetic field can be inferred from actual observations. In a subsequent contract awarded by NASA, we have continued to apply and improve the evolutionary technique, to study the physical properties of active regions, and to develop theoretical models of magnetic fields.
Determination of the coronal magnetic field from vector magnetograph data
NASA Technical Reports Server (NTRS)
Mikic, Zoran
1991-01-01
A new algorithm was developed, tested, and applied to determine coronal magnetic fields above solar active regions. The coronal field above NOAA active region AR5747 was successfully estimated on 20 Oct. 1989 from data taken at the Mees Solar Observatory of the Univ. of Hawaii. It was shown that observational data can be used to obtain realistic estimates of coronal magnetic fields. The model has significantly extended the realism with which the coronal magnetic field can be inferred from observations. The understanding of coronal phenomena will be greatly advanced by a reliable technique, such as the one presented, for deducing the detailed spatial structure of the coronal field. The payoff from major current and proposed NASA observational efforts is heavily dependent on the success with which the coronal field can be inferred from vector magnetograms. In particular, the present inability to reliably obtain the coronal field has been a major obstacle to the theoretical advancement of solar flare theory and prediction. The results have shown that the evolutional algorithm can be used to estimate coronal magnetic fields.
VECTOR MAGNETIC FIELDS OF A SOLAR POLAR REGION
Jin Chunlan; Wang Jingxiu, E-mail: cljin@nao.cas.cn, E-mail: wangjx@nao.cas.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
2011-05-01
We study the vector magnetic fields of a solar polar region (PR) based on Solar Optical Telescope/Spectro-Polarimeter measurements. To better understand the polar magnetic properties, we compare the observed polar field with that in two solar quiet regions at the limb (QRL) and the disk center (QRD), and with that in a region of a low-latitude coronal hole (CHR). The following results are discussed: (1) The average vertical flux density of PR is 16 G, while the average horizontal flux density is 91 G. If we assume that the observed polar field suffers the same amount of limb weakening in polarization measurements as the Sun's quiet region, the average unsigned flux density in the pole would be 54 G, 60% stronger than that in the CHR. (2) The kG field in the PR occupies 6.7% of the region. The magnetic filling factor in the PR is characterized by a two-peak distribution, which appears at a field strength close to 100 G and 1000 G, respectively. (3) For the network elements, a correlation holds between the vertical and horizontal flux densities, suggesting the same physical entity is manifested by the observed stronger vertical and horizontal components. (4) The ratio of the magnetic flux in the minority polarity to that in the dominant polarity is approximately 0.5, implying that only 1/3 of the magnetic flux in the PR opens to the interplanetary space. Exemplified with CHR by a quasi-linear force-free extrapolation of the observed magnetic field, we find that the photospheric open flux is not always associated with strong vertical magnetic elements.
Josephson junction interferometer device for detection of curl-free magnetic vector potential fields
Gelinas, R.C.
1985-01-01
A device for detecting and/or measuring the presence of a magnetic vector potential ''field'' including two Josephson devices in a Josephson interferometer configuration, a magnetic shielding envelope with apertures arranged so that the magnetic vector potential is confined to the vicinity of one of the two Josephson devices (but not the interferometer loop region) and a means for detecting magnetic flux induced by the interaction of the Josephson device and the magnetic vector potential ''field''. The detection of the magnetic vector potential offers a more advantageous range of dependence than the magnetic flux density.
Vector Magnetic Fields and Electric Currents from the Imaging Vector Magnetograph
Jing Li; A. A. van Ballegooijen; Don Mickey
2008-11-01
First, we describe a general procedure to produce high quality vector magnetograms using the Imaging Vector Magnetograph (IVM) at Mees Solar Observatory. At the spatial resolution 2"x2", the Stokes Q,U,V uncertainty reaches 0.001-0.0005 in time-averaged data over 1-hour in the quiet Sun. When vector magnetic fields are inferred from the time-averaged Stokes spectral images of FeI 6302.5A, the resulting uncertainties are on the order of 10 G for the longitudinal fields, 40 G for the transverse field strength and 9 degree for the magnetic azimuth. The magnetic field inversion used in this work is the "Triplet" code, which was developed and implemented in the IVM software package by the late Barry J. LaBonte. The inversion code is described in detail in the Appendix. Second, we solve for the absolute value of the vertical electric current density, |Jz|, accounting for the above IVM problems, for two different active regions. One is a single sunspot region (NOAA 10001 observed on 20 June 2002) while the other is a more complex, quadrupolar region (NOAA10030 observed on 15 July 2002). We use a calculation that does not require disambiguation of 180 degree in the transverse field directions. The |Jz| uncertainty is on the order of 7.0 mA m^-2. The vertical current density increases with increasing vertical magnetic field. The rate of increase is about 1 -2 times as large in the quadrupolar NOAA 10030 region as in the simple NOAA 10001, and it is more spatially variable over NOAA 10030 than over NOAA 10001.
Vector Magnetic Fields of Moving Magnetic Features and Flux Removal from a Sunspot
NASA Astrophysics Data System (ADS)
Kubo, M.; Shimizu, T.; Tsuneta, S.
2007-04-01
Moving magnetic features (MMFs) are small photospheric magnetic elements moving outward in the zone (moat region) surrounding mature sunspots. Vector magnetic fields and horizontal motion of the classical MMFs (called isolated MMFs hereafter) are investigated using coordinated ASP and MDI observations. Their magnetic and velocity properties are compared to nearby magnetic features, including moat fields surrounding the isolated MMFs and penumbral uncombed structure. The moat fields are defined as nonisolated MMFs because they also move outward from sunspots. The nonisolated MMFs have nearly horizontal magnetic fields of both polarities. We find that the isolated MMFs located on the lines extrapolated from the horizontal component of the uncombed structure have magnetic fields similar to the nonisolated MMFs. This suggests that the MMFs with nearly horizontal fields are intersections of horizontal fields extended from the penumbra with the photospheric surface. We find clear evidence that the isolated MMFs located on the lines extrapolated from the vertical component of the uncombed structure have vertical field lines with polarity same as the sunspot. This correspondence shows that such MMFs are detached from the spine (vertical) component of the penumbra. We estimate that the magnetic flux carried by the vertical MMFs is about 1-3 times larger than the flux loss of the sunspot. We suggest that the isolated vertical MMFs alone can transport sufficient magnetic flux and are responsible for the disappearance and disintegration of the sunspot.
VECTOR TOMOGRAPHY FOR THE CORONAL MAGNETIC FIELD. II. HANLE EFFECT MEASUREMENTS
Kramar, M. [Physics Department, The Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); Inhester, B. [Max-Planck-Institut fuer Sonnensystemforschung, Max-Plank-Str. 2, D-37191 Katlenburg-Lindau (Germany); Lin, H. [Institute for Astronomy, University of Hawaii at Manoa, 34 Ohia Ku Street, Pukalani, Maui, HI 96768 (United States); Davila, J., E-mail: maxim.i.kramar@nasa.gov, E-mail: Joseph.M.Davila@nasa.gov, E-mail: inhester@mps.mpg.de, E-mail: lin@ifa.hawaii.edu [NASA-GSFC, Code 671, Greenbelt, MD 20771 (United States)
2013-09-20
In this paper, we investigate the feasibility of saturated coronal Hanle effect vector tomography or the application of vector tomographic inversion techniques to reconstruct the three-dimensional magnetic field configuration of the solar corona using linear polarization measurements of coronal emission lines. We applied Hanle effect vector tomographic inversion to artificial data produced from analytical coronal magnetic field models with equatorial and meridional currents and global coronal magnetic field models constructed by extrapolation of real photospheric magnetic field measurements. We tested tomographic inversion with only Stokes Q, U, electron density, and temperature inputs to simulate observations over large limb distances where the Stokes I parameters are difficult to obtain with ground-based coronagraphs. We synthesized the coronal linear polarization maps by inputting realistic noise appropriate for ground-based observations over a period of two weeks into the inversion algorithm. We found that our Hanle effect vector tomographic inversion can partially recover the coronal field with a poloidal field configuration, but that it is insensitive to a corona with a toroidal field. This result demonstrates that Hanle effect vector tomography is an effective tool for studying the solar corona and that it is complementary to Zeeman effect vector tomography for the reconstruction of the coronal magnetic field.
NSDL National Science Digital Library
Dray, Tevian
2006-01-01
Vector fields are vectors which change from point to point. A standard example is the velocity of moving air, in other words, wind. For instance, the current wind pattern in the San Francisco area can be found at . This site has a 2-dimensional representation; careful reading of the webpage will tell you at what elevation the wind is shown. How would you represent a vector field in 3 dimensions? What features are important? Some simple examples are shown. Each can be rotated by clicking and dragging with the mouse. Explore!
Vector magnetic field and currents at the footpoint of a loop prominence
A. Hofmann; V. Ruždjak; B. Vrsnak
1989-01-01
Using H -filtergrams and vector magnetograms we study the structure of the magnetic field at the footpoint of a loop prominence rooting deep in the penumbral photosphere of a sunspot. In the region investigated the footpoint -field is well marked in the transversal field map. The field has a predominantly transverse character and is directed parallel to the axis of
Vector Magnetic Field and Currents at the Footpoint of a Loop Prominence
A. Hofmann; V. Ruzdjak; B. Vrsnak
1990-01-01
Using H -filtergrams and vector magnetograms we study the structure of the magnetic field at the footpoint of a loop prominence rooting deep in the penumbral photosphere of a sunspot. In the region investigated the footpoint -field is well marked in the transversal field map. The field has a predominantly transverse character and is directed parallel to the axis of
NASA Technical Reports Server (NTRS)
Tadesse, T.; Wiegelmann, T.; Gosain, S.; MacNeice, P.; Pevtsov, A. A.
2014-01-01
Context. The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently, there are several modelling techniques being used to calculate three-dimensional field lines into the solar atmosphere. Aims. For the first time, synoptic maps of a photospheric-vector magnetic field synthesized from the vector spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. Methods. We solve the nonlinear force-free field equations using an optimization principle in spherical geometry. The resulting threedimensional magnetic fields are used to estimate the magnetic free energy content E(sub free) = E(sub nlfff) - E(sub pot), which is the difference of the magnetic energies between the nonpotential field and the potential field in the global solar corona. For comparison, we overlay the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the atmospheric imaging assembly (AIA) on board the Solar Dynamics Observatory (SDO). Results. For a single Carrington rotation 2121, we find that the global nonlinear force-free field (NLFFF) magnetic energy density is 10.3% higher than the potential one. Most of this free energy is located in active regions.
Making global map of the solar surface Br from the HMI vector magnetic field observations
NASA Astrophysics Data System (ADS)
Hayashi, K.; Liu, Y.; Sun, X.; Hoeksema, J. T.; Centeno, R.; Barnes, G.; Leka, K. D.
2013-06-01
The Helioseismic Magnetic Imager (HMI) has made full-disk vector magnetic field measurements of the Sun with cadence of 12 minutes. The three-component solar surface magnetic field vector data are from the HMI observations with the data process pipeline modules, VFISV (Very Fast Inversion of the Stokes Vector, Borrero et al., 2011) for Milne-Eddington inversion and the minimum-energy disambiguation algorithm (Metcalf 1994, Leka et al, 2009). The models of the global corona and solar wind, such as the PFSS (potential-field source-surface) model and the MHD simulations, often use the maps of solar surface magnetic field, especially the radial component (Br) as the boundary condition. The HMI observation can provide new Br data for these model. Because of weak magnetic signals at the quiet regions of the Sun, the limb darkening, and geometric effects near solar poles, we need to apply an assumption to make a whole-surface map. In this paper, we tested two assumptions for determining Br at weak-field regions. The coronal structures calculated by the PFSS model with the vector-based Br are compared with those with the magnetogram-based Br and the corona observed by the SDO/AIA (Atmospheric Imaging Assembly). In the tested period, CR 2098, the vector-based Br map gives better agreements than the line-of-sight magnetogram data, though we need further investigation for evaluation.
General relation for the vector magnetic field of a circular current loop: a closer look
Robert A. Schill
2003-01-01
This paper presents a general theory for the fields generated by a circular current loop and compares it with existing theories. The existing, general, closed solution for the vector magnetic field may be expressed in a number of seemingly different but equivalent forms. These relations offer alternative closed-form solutions that may find various applications, including the characterization of Helmholtz coils.
Fast Analytical Computation of Power-Line Magnetic Fields by Complex Vector Method
Federico Moro; Roberto Turri
2008-01-01
The electromagnetic environment related to electric power installations is typically evaluated by numerical integration methods. Numerical techniques, although powerful, are not well suited for assessing the dependence of the field strength on electric and geometric parameters. In this paper, a fast procedure to analytically evaluate power-line magnetic fields, based on complex vectors, is proposed. The use of complex algebra greatly
Calculating Non-Potentiality in Solar Active Regions Using SDO/HMI Vector Magnetic Field Data
NASA Astrophysics Data System (ADS)
Bobra, M.; Hoeksema, J. T.
2010-12-01
Non-potential magnetic fields in solar active regions are thought to be associated with flare occurrence. In this study, we parametrize the non-potentiality of several active regions, using data from the Helioseismic and Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO), and correlate these parameters with flare occurrence. In particular, we focus on a parameter that we call the Gradient-Weighted Inversion Line Length (GWILL). Using data from SOHO/MDI, Mason et al. found that GWILL generally tends to increase before a solar flare. We investigate whether extending the analysis of Mason et. al. to a three-dimensional field enables us to derive better near real-time indicators of flare occurrence. Before HMI, the availability of vector magnetograms was sparse at best. HMI provides continuous vector magnetogram data at a 12-minute cadence. As such, this study represents the first parametrization of non-potentiality in solar active regions using continuous vector magnetic field data.
Obtaining vector magnetic field maps from single-component measurements of geological samples
NASA Astrophysics Data System (ADS)
Lima, Eduardo A.; Weiss, Benjamin P.
2009-06-01
Maxwell's equations can be used to demonstrate that the components of a static magnetic field in a region of space devoid of sources are not independent. This means that magnetometers that measure a single component of the magnetic field can potentially obtain all of three components of the field external to a source. Here we present an improved technique in the Fourier domain which can obtain the complete vector field planar map from just the planar map of one component. This technique is fast, robust, does not rely on any specific source type or configuration, and does not require the formulation of an inverse problem. An in-depth analysis of the advantages and shortcomings of the technique is presented, demonstrating that high-quality three-component field maps with virtually no information loss can be obtained when proper sensor and mapping configurations are used. Several results derived from both synthetic and experimental data are presented. In particular, practical cases are shown where vector maps can assist the analysis of magnetic properties of geological samples. MATLAB® routines implementing the basic vector map calculation algorithm are available as auxiliary materials and can be readily adapted for processing magnetic data obtained from a variety of magnetic sensors.
Low-Magnetic-Field Control of Electric Polarization Vector in a Helimagnet
NASA Astrophysics Data System (ADS)
Ishiwata, Shintaro; Taguchi, Yasujiro; Murakawa, Hiroshi; Onose, Yoshinori; Tokura, Yoshinori
2008-03-01
The mutual control of the electric and magnetic properties of a solid is currently of great interest because of the possible application for novel electronic devices. We report on the low-magnetic-field (for example, B values of ±30 milliteslas) control of the polarization (P) vector in a hexaferrite, Ba2Mg2Fe12O22, which shows the helimagnetic spin structure with the propagation vector k0 parallel to [001]. The B-induced transverse conical spin structure carries the P vector directing perpendicular to both B and k0, in accord with the recently proposed spin-current model. Then, the oscillating or multidirectionally rotating B produces the cyclic displacement current via the flexible handling of the magnetic cone axis.
VECTOR MAGNETIC FIELDS AND CURRENT HELICITIES IN CORONAL HOLES AND QUIET REGIONS
Yang Shuhong; Zhang Jun; Li Ting [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Ding Mingde, E-mail: shuhongyang@nao.cas.cn, E-mail: zjun@nao.cas.cn, E-mail: liting@nao.cas.cn, E-mail: dmd@nju.edu.cn [Department of Astronomy, Nanjing University, Nanjing 210093 (China)
2011-01-01
In the solar photosphere, many properties of coronal holes (CHs) are not known, especially vector magnetic fields. Using observations from Hinode, we investigate vector magnetic fields, current densities, and current helicities in two CHs, and compare them with two normal quiet regions (QRs) for the first time. We find that the areas where large current helicities are located are mainly co-spatial with strong vertical and horizontal field elements both in shape and in location. In the CHs, horizontal magnetic fields, inclination angles, current densities, and current helicities are larger than those in the QRs. The mean vertical current density and current helicity in the CHs and QRs, averaged over all the observed areas including the CHs and QRs, are approximately 0.008 A m{sup -2} and 0.005 G{sup 2} m{sup -1}, respectively. The mean current density in magnetic flux concentrations where the vertical fields are stronger than 100 G is as large as 0.012 {+-} 0.001 A m{sup -2}, consistent with that in the flare productive active regions. Our results imply that the magnetic fields, especially the strong fields, both in the CHs and in the QRs are nonpotential.
He I vector magnetic field maps of a sunspot and its superpenumbral fine-structure
Schad, T A; Lin, H; Tritschler, A
2015-01-01
Advanced inversions of high-resolution spectropolarimetric observations of the He I triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions, as superpenumbral Stokes profiles are dominated by atomic-level polarization while sunspot profiles are Zeeman-dominated but also exhibit signatures perhaps induced by symmetry breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere, and further show that the superpenumbral magnetic field does not appear finely structured, unlike the observed intensity structure. This suggests fibrils are not concentrations of magnetic flux but rather distinguished by individualized thermalization. We also dire...
NASA Astrophysics Data System (ADS)
Kotsiaros, Stavros; Finlay, Chris; Olsen, Nils
2015-04-01
One of the main goals of the Swarm three-satellite constellation mission is to determine the lithospheric field globally with the best possible resolution. To achieve that, explicit advantage of the constellation aspect of Swarm has to be taken by using gradient estimates. We derive lithospheric field models using more than one year of East-West and North-South magnetic gradient data, approximated by first differences of field vector data between the two lower Swarm satellites and along each satellite orbit, respectively. Despite the current relatively high altitude of 450 km of the Swarm satellites, the results are promising. We find that Swarm gradient data are less sensitive to large-scale external field fluctuations and enhance the resolution of the determined lithospheric field compared to only vector data. The derived models agree very well with previous models derived from CHAMP data, serving as an initial validation of the Swarm mission.
HMI vector magnetic field products: the long-awaited release has come! Now what?
NASA Astrophysics Data System (ADS)
Centeno, R.; Barnes, G.; Borrero, J.; Couvidat, S. P.; Hayashi, K.; Hoeksema, J. T.; Leka, K. D.; Liu, Y.; Schou, J.; Schuck, P. W.; Sun, X.; Tomczyk, S.
2011-12-01
HMI vector magnetic field test products will be released, alongside with the corresponding documentation, soon after the submission of this abstract. These data represent a stage of the project at which the HMI vector team has a large degree of confidence in the results. However, longer-term research topics on how to improve certain aspects of the data pipeline in general -and the spectral line inversion code in particular- are being pursued as we get valuable input from the user community. I will give a brief summary of the characteristics of the released inversion data products and an update of where we stand now.
Interior Vector Magnetic Field Monitoring for the SNS Neutron EDM Experiment
NASA Astrophysics Data System (ADS)
Nouri, Nima; Plaster, Brad
2014-09-01
A concept has been developed which provides for a real-time determination of the spatial dependence of the vector components of the magnetic field (and, hence, the ?Bi / ?xj field gradients) within the interior fiducial volume of the SNS neutron EDM experiment solely from exterior measurements at fixed discrete locations. This technique will be especially important during the operation of the experiment, when direct measurements of the field gradients present within the fiducial volume will not be physically possible. Our method, which is based on the solution to the Laplace Equation, is completely general and does not require the field to possess any type of symmetry. We describe the concept and our systematic approach for optimizing the locations of these exterior measurements. We also present results from prototyping studies of a field monitoring system deployed within a half-scale prototype of the experiment's magnetic field environment. A concept has been developed which provides for a real-time determination of the spatial dependence of the vector components of the magnetic field (and, hence, the ?Bi / ?xj field gradients) within the interior fiducial volume of the SNS neutron EDM experiment solely from exterior measurements at fixed discrete locations. This technique will be especially important during the operation of the experiment, when direct measurements of the field gradients present within the fiducial volume will not be physically possible. Our method, which is based on the solution to the Laplace Equation, is completely general and does not require the field to possess any type of symmetry. We describe the concept and our systematic approach for optimizing the locations of these exterior measurements. We also present results from prototyping studies of a field monitoring system deployed within a half-scale prototype of the experiment's magnetic field environment. This work was supported in part by the U.S. Department of Energy Office of Nuclear Physics under Award No. DE-FG02-08ER41557.
NASA Astrophysics Data System (ADS)
Su, J. T.; Zhang, H. Q.
2007-09-01
Observations of full-disk solar photospheric vector magnetic fields are very important for the studies of the global properties and evolution of solar magnetism. Such observations can allow us to investigate the magnetic connectivities between active regions and the nonpotentiality of magnetic fields with a much wider field of view (FOV) than do local-region observations. Therefore, we developed a full-disk vector magnetograph for the Solar Magnetism and Activity Telescope (SMAT) at Huairou Solar Observing Station. In this paper, we point out two problems that affect measurement accuracy of full-disk vector magnetic fields: circular-to-linear polarization crosstalk produced by the instrument, and wavelength shift due to solar rotation. An attempt is made to correct such polarization crosstalk and to reconstruct full-disk vector magnetic fields from polarization data. We also give a superficial discussion about the problem of an incompletely wide field of view (IWFOV) of the Lyot filter in the measurements of full-disk solar vector magnetic fields. In addition, the polarization data of the SMAT are compared with those of the Solar Magnetic Field Telescope (SMFT), which operates the local-region observations. Although the SMFT is 2-3 times as sensitive as the SMAT, there is a basic agreement on the polarization data of the two instruments.
Thalmann, J. K.; Tiwari, S. K.; Wiegelmann, T., E-mail: thalmann@mps.mpg.de [Max-Plank-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)
2013-05-20
Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope's Spectropolarimeter (SP) on board Hinode. Besides basing our model calculations on HMI data, we use both SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate how a binning of high-resolution data affects the model outcome. The resulting three-dimensional magnetic fields are compared in terms of magnetic energy content and magnetic topology. We find stronger magnetic fields in the SP data, translating into a higher total magnetic energy of the SP models. The net Lorentz forces of the HMI and SP lower boundaries verify their force-free compatibility. We find substantial differences in the absolute estimates of the magnetic field energy but similar relative estimates, e.g., the fraction of excess energy and of the flux shared by distinct areas. The location and extension of neighboring connectivity domains differ and the SP model fields tend to be higher and more vertical. Hence, conclusions about the magnetic connectivity based on force-free field models are to be drawn with caution. We find that the deviations of the model solution when based on the lower-resolution SP data are small compared to the differences of the solutions based on data from different instruments.
The Z3 model of Saturns magnetic field and the Pioneer 11 vector helium magnetometer observations
NASA Technical Reports Server (NTRS)
Connerney, J. E. P.; Acuna, M. H.; Ness, N. F.
1984-01-01
Magnetic field observations obtained by the Pioneer 11 vector helium magnetometer are compared with the Z(sub 3) model magnetic field. These Pioneer 11 observations, obtained at close-in radial distances, constitute an important and independent test of the Z(sub 3) zonal harmonic model, which was derived from Voyager 1 and Voyager 2 fluxgate magnetometer observations. Differences between the Pioneer 11 magnetometer and the Z(sub 3) model field are found to be small (approximately 1%) and quantitatively consistent with the expected instrumental accuracy. A detailed examination of these differences in spacecraft payload coordinates shows that they are uniquely associated with the instrument frame of reference and operation. A much improved fit to the Pioneer 11 observations is obtained by rotation of the instrument coordinate system about the spacecraft spin axis by 1.4 degree. With this adjustment, possibly associated with an instrumental phase lag or roll attitude error, the Pioneer 11 vector helium magnetometer observations are fully consistent with the Voyager Z(sub 3) model.
Elizabeth A. Ainsbury; Emma Conein; Denis L. Henshaw
2005-01-01
Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz
Optical Tomography of a Sunspot. II. Vector Magnetic Field and Temperature Stratification
NASA Astrophysics Data System (ADS)
Westendorp Plaza, C.; del Toro Iniesta, J. C.; Ruiz Cobo, B.; Martínez Pillet, V.; Lites, B. W.; Skumanich, A.
2001-02-01
An observational determination of the three-dimensional magnetic and thermal structure of a sunspot is presented. It has been obtained through the application of the SIR inversion technique (Stokes Inversion based on Response functions) on a low-noise, full Stokes profile two-dimensional map of the sunspot as observed with the Advanced Stokes Polarimeter. As a result of the inversion, maps of the magnetic field strength, B, zenith angle, ?, azimuth, ?, and temperature, T, over 25 layers at given optical depths (i.e., an optical tomography) are obtained, of which those between log?5=0 and log?5=-2.8 are considered to provide accurate information on the physical parameters. All over the penumbra ? increases with depth, while B is larger at the bottom layers of the inner penumbra (as in the umbra) but larger at the top layers of the outer penumbra (as in the canopy). The corrugation of the penumbral magnetic field already observed by other authors has been confirmed by our different inversion technique. Such a corrugation is especially evident in the zenith angle maps of the intermediate layers, featuring the presence of the so-called spines that we further characterize: spines are warmer and have a less inclined magnetic field than the spaces between them and tend to have a smaller gradient of ? with optical depth over the entire penumbra, but with a field strength which is locally stronger in the middle penumbra and locally weaker in the outer penumbra and beyond in the canopy. In the lower layers of these external parts of the sunspot, most of the field lines are seen to return to the solar surface, a result that is closely connected with the Evershed effect (e.g., Westendorp et al., the third paper in this series). The Stokes V net area asymmetry map as well as the average B, ?, and T radial distributions (and that of the line-of-sight velocities; see the third paper in this series) show a border between an inner and an outer penumbra with different three-dimensional structure. We suggest that it is in this middle zone where most of a new family of penumbral flux tubes (some of them with Evershed flow) emerge interlaced (both horizontally and vertically) among themselves and with the ``background'' magnetic field of the penumbra. The interlacing along the line of sight is witnessed by the indication of many points in the outer penumbra showing rapid transitions with height between two structures, one with very weak and inclined magnetic field at the bottom of the photosphere and the other with a stronger and less inclined magnetic field. Over the whole penumbra, and at all optical layers, a constant but weak deviation from radiality of some 5° is detected for the azimuth of the vector magnetic field, which may be in agreement with former detections but which is not significantly higher than the size of the errors for this parameter.
NASA Astrophysics Data System (ADS)
Velasco-Martínez, D.; Ibarra-Sierra, V. G.; Sandoval-Santana, J. C.; Kunold, A.; Cardoso, J. L.
2014-09-01
In this paper we introduce an alternative approach to studying the motion of a planar charged particle subject to a static uniform magnetic field. It is well known that an electric charge under a uniform magnetic field has a planar motion if its initial velocity is perpendicular to the magnetic field. Although some constants of motion (CsM), as the energy and the angular momentum, have been widely discussed for this system, others have been neglected. We find that the angular momentum, the generator of the magnetic translations and the magnetic Laplace-Runge-Lenz vector are CsM for this particular system. We show also that these three quantities form an orthogonal basis of vectors. The present work addresses many aspects of the motion of a charged particle in a magnetic field that should be useful for students and tutors of the classical mechanics courses at the senior undergraduate level.
NASA Astrophysics Data System (ADS)
Wiegelmann, T.; Thalmann, J. K.; Inhester, B.; Tadesse, T.; Sun, X.; Hoeksema, J. T.
2012-11-01
The Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) provides photospheric vector magnetograms with a high spatial and temporal resolution. Our intention is to model the coronal magnetic field above active regions with the help of a nonlinear force-free extrapolation code. Our code is based on an optimization principle and has been tested extensively with semianalytic and numeric equilibria and applied to vector magnetograms from Hinode and ground-based observations. Recently we implemented a new version which takes into account measurement errors in photospheric vector magnetograms. Photospheric field measurements are often affected by measurement errors and finite nonmagnetic forces inconsistent for use as a boundary for a force-free field in the corona. To deal with these uncertainties, we developed two improvements: i) preprocessing of the surface measurements to make them compatible with a force-free field, and ii) new code which keeps a balance between the force-free constraint and deviation from the photospheric field measurements. Both methods contain free parameters, which must be optimized for use with data from SDO/HMI. In this work we describe the corresponding analysis method and evaluate the force-free equilibria by how well force-freeness and solenoidal conditions are fulfilled, by the angle between magnetic field and electric current, and by comparing projections of magnetic field lines with coronal images from the Atmospheric Imaging Assembly (SDO/AIA). We also compute the available free magnetic energy and discuss the potential influence of control parameters.
Observations of vector magnetic fields with a magneto-optic filter
NASA Technical Reports Server (NTRS)
Cacciani, Alessandro; Varsik, John; Zirin, Harold
1990-01-01
The use of the magnetooptic filter to observe solar magnetic fields in the potassium line at 7699 A is described. The filter has been used in the Big Bear videomagnetograph since October 23. It gives a high sensitivity and dynamic range for longitudnal magnetic fields and enables measurement of transverse magnetic fields using the sigma component. Examples of the observations are presented.
NASA Astrophysics Data System (ADS)
Du, Jinsong; Chen, Chao; Lesur, Vincent; Lane, Richard; Wang, Huilin
2015-06-01
We examined the mathematical and computational aspects of the magnetic potential, vector and gradient tensor fields of a tesseroid in a geocentric spherical coordinate system (SCS). This work is relevant for 3-D modelling that is performed with lithospheric vertical scales and global, continent or large regional horizontal scales. The curvature of the Earth is significant at these scales and hence, a SCS is more appropriate than the usual Cartesian coordinate system (CCS). The 3-D arrays of spherical prisms (SP; `tesseroids') can be used to model the response of volumes with variable magnetic properties. Analytical solutions do not exist for these model elements and numerical or mixed numerical and analytical solutions must be employed. We compared various methods for calculating the response in terms of accuracy and computational efficiency. The methods were (1) the spherical coordinate magnetic dipole method (MD), (2) variants of the 3-D Gauss-Legendre quadrature integration method (3-D GLQI) with (i) different numbers of nodes in each of the three directions, and (ii) models where we subdivided each SP into a number of smaller tesseroid volume elements, (3) a procedure that we term revised Gauss-Legendre quadrature integration (3-D RGLQI) where the magnetization direction which is constant in a SCS is assumed to be constant in a CCS and equal to the direction at the geometric centre of each tesseroid, (4) the Taylor's series expansion method (TSE) and (5) the rectangular prism method (RP). In any realistic application, both the accuracy and the computational efficiency factors must be considered to determine the optimum approach to employ. In all instances, accuracy improves with increasing distance from the source. It is higher in the percentage terms for potential than the vector or tensor response. The tensor errors are the largest, but they decrease more quickly with distance from the source. In our comparisons of relative computational efficiency, we found that the magnetic potential takes less time to compute than the vector response, which in turn takes less time to compute than the tensor gradient response. The MD method takes less time to compute than either the TSE or RP methods. The efficiency of the (GLQI and) RGLQI methods depends on the polynomial order, but the response typically takes longer to compute than it does for the other methods. The optimum method is a complex function of the desired accuracy, the size of the volume elements, the element latitude and the distance between the source and the observation. For a model of global extent with typical model element size (e.g. 1 degree horizontally and 10 km radially) and observations at altitudes of 10s to 100s of km, a mixture of methods based on the horizontal separation of the source and observation separation would be the optimum approach. To demonstrate the RGLQI method described within this paper, we applied it to the computation of the response for a global magnetization model for observations at 300 and 30 km altitude.
Castro, Luis B
2015-01-01
The quantum dynamics of a spin-1/2 charged particle in the presence of magnetic field is analyzed for the general case where scalar and vector couplings are considered. The energy spectra are explicitly computed for different physical situations, as well as their dependencies on the magnetic field strength, spin projection parameter and vector and scalar coupling constants.
NASA Astrophysics Data System (ADS)
Ford, Kris; Mair, Lamar; Fisher, Mike; Rowshon Alam, Md.; Juliano, Rudolph; Superfine, Richard
2008-10-01
In order to make non-viral gene delivery a useful tool in the study and treatment of genetic disorders, it is imperative that these methodologies be further refined to yield optimal results. Transfection of magnetic nanoparticles and nanorods are used as non-viral gene vectors to transfect HeLa EGFP-654 cells that stably express a mutated enhanced green fluorescent protein (EGFP) gene. We deliver antisense oligonucleotides to these cells designed to correct the aberrant splicing caused by the mutation in the EGFP gene. We also transfect human bronchial endothelial cells and immortalized WI-38 lung cells with pEGFP-N1 vectors. To achieve this we bind the genes to magnetic nanoparticles and nanorods and introduce magnetic fields to effect transfection. We wish to examine the effects of magnetic fields on the transfection of these particles and the benefits of using alternating (AC) magnetic fields in improving transfection rates over direct (DC) magnetic fields. We specifically look at the frequency dependence of the AC field and particle aspect ratio as it pertains to influencing transfection rate. We posit that the increase in angular momentum brought about by the AC field and the high aspect ratio of the nanorod particles, is vital to generating the force needed to move the particle through the cell membrane.
Gosain, S.; Pevtsov, A. A. [National Solar Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Rudenko, G. V.; Anfinogentov, S. A. [Institute of Solar-Terrestrial Physics (ISTP), Russian Academy of Sciences, Irkutsk (Russian Federation)
2013-07-20
We use daily full-disk vector magnetograms from Vector Spectromagnetograph on Synoptic Optical Long-term Investigations of the Sun system to synthesize the first Carrington maps of the photospheric vector magnetic field. We describe these maps and make a comparison of the observed radial field with the radial field estimate from line-of-sight magnetograms. Furthermore, we employ these maps to study the hemispheric pattern of current helicity density, H{sub c} , during the rising phase of solar cycle 24. The longitudinal average over the 23 consecutive solar rotations shows a clear signature of the hemispheric helicity rule, i.e., H{sub c} is predominantly negative in the north and positive in the south. Although our data include the early phase of cycle 24, there appears to be no evidence for a possible (systematic) reversal of the hemispheric helicity rule at the beginning of the cycle as predicted by some dynamo models. Furthermore, we compute the hemispheric pattern in active region latitudes (-30 Degree-Sign {<=} {theta} {<=} 30 Degree-Sign ) separately for weak (100 G < |B{sub r} | < 500 G) and strong (|B{sub r} | > 1000 G) radial magnetic fields. We find that while the current helicity of strong fields follows the well-known hemispheric rule (i.e., {theta} {center_dot} H{sub c} < 0), H{sub c} of weak fields exhibits an inverse hemispheric behavior (i.e., {theta} {center_dot} H{sub c} > 0), albeit with large statistical scatter. We discuss two plausible scenarios to explain the opposite hemispheric trend of helicity in weak and strong field regions.
NASA Astrophysics Data System (ADS)
Ainsbury, Elizabeth A.; Conein, Emma; Henshaw, Denis L.
2005-07-01
Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 ± 0.02 µT across all residences. In contrast, background field ellipticities were high, on average 47 ± 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 ± 21% and 21 ± 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure. This work is supported by the charity CHILDREN with LEUKAEMIA, registered charity number 298405.
Ainsbury, Elizabeth A; Conein, Emma; Henshaw, Denis L
2005-07-01
Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0-3000 Hz magnetic fields, produced by 226 domestic mains-fed appliances of 32 different types, were carried out in 16 homes in Worcestershire in the summer of 2004. Magnetic field strengths were low, with average (RMS) values of 0.03 +/- 0.02 microT across all residences. In contrast, background field ellipticities were high, on average 47 +/- 11%. Microwave and electric ovens produced the highest ellipticities: mean respective values of 21 +/- 21% and 21 +/- 17% were observed 20 cm away from these appliances. There was a negative correlation between field strength and field polarization, which we attribute to the higher relative field contribution close to each individual (single-phase) appliance. The measurements demonstrate that domestic magnetic fields are extremely complex and cannot simply be characterized by traditional measurements such as time-weighted average or peak exposure levels. We conclude that ellipticity should become a relevant metric for future epidemiological studies of health and ELF-MF exposure. PMID:15972990
He uc(i) Vector Magnetic Field Maps of a Sunspot and Its Superpenumbral Fine-Structure
NASA Astrophysics Data System (ADS)
Schad, T. A.; Penn, M. J.; Lin, H.; Tritschler, A.
2015-06-01
Advanced inversions of high-resolution spectropolarimetric observations of the He uc(i) triplet at 1083 nm are used to generate unique maps of the chromospheric magnetic field vector across a sunspot and its superpenumbral canopy. The observations were acquired by the Facility Infrared Spectropolarimeter (FIRS) at the Dunn Solar Telescope (DST) on 29 January 2012. Multiple atmospheric models are employed in the inversions because superpenumbral Stokes profiles are dominated by atomic-level polarization, while sunspot profiles are Zeeman-dominated, but also exhibit signatures that might be induced by symmetry-breaking effects of the radiation field incident on the chromospheric material. We derive the equilibrium magnetic structure of a sunspot in the chromosphere and furthermore show that the superpenumbral magnetic field does not appear to be finely structured, unlike the observed intensity structure. This suggests that fibrils are not concentrations of magnetic flux, but are instead distinguished by individualized thermalization. We also directly compare our inverted values with a current-free extrapolation of the chromospheric field. With improved measurements in the future, the average shear angle between the inferred magnetic field and the potential field may offer a means to quantify the non-potentiality of the chromospheric magnetic field to study the onset of explosive solar phenomena.
NASA Technical Reports Server (NTRS)
Hewagama, Tilak; Deming, Drake; Jennings, Donald E.; Osherovich, Vladimir; Wiedemann, Gunter; Zipoy, David; Mickey, Donald L.; Garcia, Howard
1993-01-01
Polarimetric observations at 12 microns of two sunpots are reported. The horizontal distribution of parameters such as magnetic field strength, inclination, azimuth, and magnetic field filling factors are presented along with information about the height dependence of the magnetic field strength. Comparisons with contemporary magnetostatic sunspot models are made. The magnetic data are used to estimate the height of 12 micron line formation. From the data, it is concluded that within a stable sunspot there are no regions that are magnetically filamentary, in the sense of containing both strong-field and field-free regions.
Obtaining vector magnetic field maps from single-component measurements of geological samples
Andrade Lima, Eduardo
Maxwell's equations can be used to demonstrate that the components of a static magnetic field in a region of space devoid of sources are not independent. This means that magnetometers that measure a single component of the ...
NASA Astrophysics Data System (ADS)
Centeno, R.; Schou, J.; Hayashi, K.; Norton, A.; Hoeksema, J. T.; Liu, Y.; Leka, K. D.; Barnes, G.
2014-09-01
The Very Fast Inversion of the Stokes Vector (VFISV) is a Milne-Eddington spectral line inversion code used to determine the magnetic and thermodynamic parameters of the solar photosphere from observations of the Stokes vector in the 6173 Å Fe i line by the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). We report on the modifications made to the original VFISV inversion code in order to optimize its operation within the HMI data pipeline and provide the smoothest solution in active regions. The changes either sped up the computation or reduced the frequency with which the algorithm failed to converge to a satisfactory solution. Additionally, coding bugs which were detected and fixed in the original VFISV release are reported here.
NASA Astrophysics Data System (ADS)
Belinsky, Moisey I.
2014-05-01
Correlations between field-dependent planar spin configurations, degenerate frustration, energy, vector ?z and scalar ? chiralities, spin canting, total, in-plane staggered and intermediate spin (IS) magnetizations are considered for the V3, Cu nanomagnets in transverse B?Z magnetic field. The planar spin configurations in Bx?X are characterized by the variable axial ?z(Bx) vector chirality correlated with the total in-plane magnetization Mx(Bx) and the IS magnetization M?12±(Bx), which describes the IS S12 behavior, ?(B?)=0. The in-plane staggered magnetization determines the magnitude of the vector chirality ?z. The low-field frustrated planar 120° configurations are transformed by increasing Bx field into the high-field achiral planar spin-collinear configurations. This transition is accompanied by the reduction of the vector chirality ?z and simultaneous increase of the total Mx(Bx) and IS M?12±(Bx) magnetizations. The spin configurations, chiralities and magnetization are highly anisotropic. In longitudinal B?Z field, the frustrated longitudinal spin-collinear configurations are characterized by the correlated maximal vector and scalar chiralities, ?=2?zMz.
NASA Astrophysics Data System (ADS)
Leka, K. D.; Barnes, Graham; Crouch, A. D.; Metcalf, Thomas R.; Gary, G. Allen; Jing, Ju; Liu, Y.
2009-11-01
The objective testing of algorithms for performing ambiguity resolution in vector magnetic field data is continued, with an examination of the effects of noise in the data. Through the use of analytic magnetic field models, two types of noise are “added” prior to resolving: noise to simulate Poisson photon noise in the observed polarization spectra, and a spatial binning to simulate the effects of unresolved structure. The results are compared through the use of quantitative metrics and performance maps. We find that while no algorithm severely propagates the effects of Poisson noise beyond very local influences, some algorithms are more robust against high photon-noise levels than others. In the case of limited spatial resolution, loss of information regarding fine-scale structure can easily result in erroneous solutions. Our tests imply that photon noise and limited spatial resolution can act so as to make assumptions used in some ambiguity resolution algorithms no longer consistent with the observed magnetogram. We confirm a finding of the earlier comparison study that results can be very sensitive to the details of the treatment of the observed boundary and the assumptions governing that treatment. We discuss the implications of these findings, given the relative sensitivities of the algorithms to the two sources of noise tested here. We also touch on further implications for interpreting observational vector magnetic field data for general solar physics research.
NASA Astrophysics Data System (ADS)
Hayashi, K.; Hoeksema, J. T.; Liu, Y.; Bobra, M. G.; Sun, X. D.; Norton, A. A.
2015-05-01
Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of the Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic and Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of a polytropic gas with specific-heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on a daily basis. The MHD data available in the JSOC database are three-dimensional, covering heliocentric distances from 1.025 to 4.975 solar radii, and contain all eight MHD variables: the plasma density, temperature, and three components of motion velocity, and three components of the magnetic field. This article describes details of the MHD simulations as well as the production of the input magnetic-field maps, and details of the products available at the JSOC database interface. To assess the merits and limits of the model, we show the simulated data in early 2011 and compare with the actual coronal features observed by the Atmospheric Imaging Assembly (AIA) and the near-Earth in-situ data.
Hayashi, Keiji; Liu, Yang; Bobra, Monica G; Sun, Xudong D; Norton, Aimee A
2015-01-01
Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of polytropic gas with specific heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on daily basis. The MHD data available in the JSOC database are three-dimen...
Mariappan, Leo; Hu, Gang; He, Bin
2014-01-01
Purpose: Magnetoacoustic tomography with magnetic induction (MAT-MI) is an imaging modality to reconstruct the electrical conductivity of biological tissue based on the acoustic measurements of Lorentz force induced tissue vibration. This study presents the feasibility of the authors' new MAT-MI system and vector source imaging algorithm to perform a complete reconstruction of the conductivity distribution of real biological tissues with ultrasound spatial resolution. Methods: In the present study, using ultrasound beamformation, imaging point spread functions are designed to reconstruct the induced vector source in the object which is used to estimate the object conductivity distribution. Both numerical studies and phantom experiments are performed to demonstrate the merits of the proposed method. Also, through the numerical simulations, the full width half maximum of the imaging point spread function is calculated to estimate of the spatial resolution. The tissue phantom experiments are performed with a MAT-MI imaging system in the static field of a 9.4 T magnetic resonance imaging magnet. Results: The image reconstruction through vector beamformation in the numerical and experimental studies gives a reliable estimate of the conductivity distribution in the object with a ?1.5 mm spatial resolution corresponding to the imaging system frequency of 500 kHz ultrasound. In addition, the experiment results suggest that MAT-MI under high static magnetic field environment is able to reconstruct images of tissue-mimicking gel phantoms and real tissue samples with reliable conductivity contrast. Conclusions: The results demonstrate that MAT-MI is able to image the electrical conductivity properties of biological tissues with better than 2 mm spatial resolution at 500 kHz, and the imaging with MAT-MI under a high static magnetic field environment is able to provide improved imaging contrast for biological tissue conductivity reconstruction. PMID:24506649
NSDL National Science Digital Library
2014-09-18
Students visualize the magnetic field of a strong permanent magnet using a compass. The lesson begins with an analogy to the effect of the Earth's magnetic field on a compass. Students see the connection that the compass simply responds to the Earth's magnetic field since it is the closest, strongest field, and thus the compass responds to the field of the permanent magnets, allowing them the ability to map the field of that magnet in the activity. This information will be important in designing a solution to the grand challenge in activity 4 of the unit.
NASA Astrophysics Data System (ADS)
Akbar Rajabi, Ali; Hamzavi, Majid
2013-01-01
The Cornellpotential consists of linear and Coulomb potentials, i.e. - a/ r+ br, and has attracted a great deal of attention in particle physics. In this article, we study the energy levels and the wave function for an arbitrary m-state in the two-dimensional (2D) Klein-Gordon (KG) equation with the unequal scalar-vector Cornell potentials under the influence of strong external uniform magnetic and Aharonov-Bohm (AB) flux fields perpendicular to the plane where the interacting particles are confined. We use the wave function ansatz method to solve the radial problem of the KG equation with the Cornell potential. We obtain the energy levels in the absence of external fields and also find the energy levels of the familiar Coulomb and harmonic oscillator potentials.
Schöller, Markus
2015-01-01
In this chapter, we give a brief introduction into the use of the Zeeman effect in astronomy and the general detection of magnetic fields in stars, concentrating on the use of FORS2 for longitudinal magnetic field measurements.
D. V. Anderson; J. Breazeal; C. H. Finan; B. M. Johnston
1976-01-01
ABCXYZ is a computer code for obtaining the Cartesian components of the vector potential and the magnetic field on an observed grid from an arrangement of current-carrying wires. Arbitrary combinations of straight line segments, arcs, and loops are allowed in the specification of the currents. Arbitrary positions and orientations of the current-carrying elements are also allowed. Specification of the wire
NASA Technical Reports Server (NTRS)
Skumanich, A.; Lites, B. W.
1985-01-01
The least square fitting of Stokes observations of sunspots using a Milne-Eddington-Unno model appears to lead, in many circumstances, to various inconsistencies such as anomalously large doppler widths and, hence, small magnetic fields which are significantly below those inferred solely from the Zeeman splitting in the intensity profile. It is found that the introduction of additional physics into the model such as the inclusion of damping wings and magneto-optic birefrigence significantly improves the fit to Stokes parameters. Model fits excluding the intensity profile, i.e., of both magnitude as well as spectral shape of the polarization parameters alone, suggest that parasitic light in the intensity profile may also be a source of inconsistencies. The consequences of the physical changes on the vector properties of the field derived from the Fe I lambda 6173 line for the 17 November 1975 spot as well as on the thermodynamic state are discussed. A Doppler width delta lambda (D) - 25mA is bound to be consistent with a low spot temperature and microturbulence, and a damping constant of a = 0.2.
Magnetic Field Safety Magnetic Field Safety
McQuade, D. Tyler
Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain fields will rapidly accelerate any magnetic material towards the magnet. § Magnetic material is commonly
Denoising 2-D Vector Fields by Vector Wavelet Thresholding
Westenberg, Michel A.
Denoising 2-D Vector Fields by Vector Wavelet Thresholding Michel A. Westenberg and Thomas Ertl for denoising 2-D vector fields that are corrupted by additive noise. The method is based on the vector wavelet introduce modifications to scalar wavelet coefficient thresholding for dealing with vector
Vector fields in multidimensional cosmology
Boris E. Meierovich
2011-10-06
Vector fields in the expanding Universe are considered within the multidimensional theory of General Relativity. Vector fields in general relativity form a three-parametric variety. Our consideration includes the fields with a nonzero covariant divergence. Depending on the relations between the particular parameters and the symmetry of a problem, the vector fields can be longitudinal and/or transverse, ultrarelativistic (i.e. massless) or nonrelativistic (massive), and so on. The longitudinal and transverse vector fields are considered separately in detail in the background of the de Sitter cosmological metric. In most cases the field equations reduce to Bessel equations, and their temporal evolution is analyzed analytically. The energy-momentum tensor of the most simple zero-mass longitudinal vector fields enters the Einstein equations as an additive to the cosmological constant. In this case the de Sitter metric is the exact solution of the Einstein equations. Hence, the most simple zero-mass longitudinal vector field pretends to be an adequate tool for macroscopic description of dark energy as a source of the expansion of the Universe at a constant rate. The zero-mass vector field does not vanish in the process of expansion. On the contrary, massive fields vanish with time. Though their amplitude is falling down, the massive fields make the expansion accelerated. The macroscopic analysis of vector fields in cosmology gives up the hope that the major puzzle -- attraction between individual objects and expansion of the Universe as a whole -- can be solved within the Einstein's theory of general relativity.
NASA Astrophysics Data System (ADS)
Li, Dandan; Liu, Fugui; Li, Yongjian; Zhao, Zhigang; Zhang, Changgeng; Yang, Qingxin
2014-05-01
A 2-D vector hybrid hysteresis model for a soft magnetic composite (SMC) material is established, which is combined with classical Preisach model and Stoner-Wohlfarth (S-W) model. The rotational magnetic properties of SMC materials were studied using the vector model, and the computed results were compared with the experimental measurement. It is shown that the vector hybrid model can effectively simulate the rotational magnetic properties under low magnetization fields.
Shear angle of magnetic fields.
NASA Astrophysics Data System (ADS)
Yanping, Lü; Wang, Jingxiu; Wang, Huaning
1993-11-01
The authors introduce a new parameter, the shear angle of vector magnetic fields, ??, to describe the non-potentiality of magnetic fields in active regions, which is defined as the angle between the observed vector magnetic field and its corresponding current-free field. In the case of highly inclined field configurations, this angle is approximately equal to the "angular shear", ??, defined by Hagyard et al. (1984). ?? can be considered as the projection of the shear angle, ??, on the photosphere. For the active region studied, the shear angle, ??, seems to have a better and neater correspondence with flare activity than does ??. It gives a clearer explanation of the non-potentiality of magnetic fields. It is a better measure of the deviation of the observed magnetic field from a potential field, and is directly related to the magnetic free energy stored in non-potential fields.
Inflation with Massive Vector Fields
Junyu Liu; Yi Wang; Siyi Zhou
2015-02-26
We investigate the coupling between the inflaton and massive vector fields. All renormalizable couplings with shift symmetry of the inflaton are considered. The massive vector can be decomposed into a scalar mode and a divergence-free vector mode. We show that the former naturally interacts with the inflaton and the latter decouples at tree level. The model in general predicts $f_{NL}^\\mathrm{equil} = \\mathcal{O}(1)$, while in some regions of the parameter space large non-Gaussianity can arise.
Magnetic nanoparticle motion in external magnetic field
NASA Astrophysics Data System (ADS)
Usov, N. A.; Liubimov, B. Ya
2015-07-01
A set of equations describing the motion of a free magnetic nanoparticle in an external magnetic field in a vacuum, or in a medium with negligibly small friction forces is postulated. The conservation of the total particle momentum, i.e. the sum of the mechanical and the total spin momentum of the nanoparticle is taken into account explicitly. It is shown that for the motion of a nanoparticle in uniform magnetic field there are three different modes of precession of the unit magnetization vector and the director that is parallel the particle easy anisotropy axis. These modes differ significantly in the precession frequency. For the high-frequency mode the director points approximately along the external magnetic field, whereas the frequency and the characteristic relaxation time of the precession of the unit magnetization vector are close to the corresponding values for conventional ferromagnetic resonance. On the other hand, for the low-frequency modes the unit magnetization vector and the director are nearly parallel and rotate in unison around the external magnetic field. The characteristic relaxation time for the low-frequency modes is remarkably long. This means that in a rare assembly of magnetic nanoparticles there is a possibility of additional resonant absorption of the energy of alternating magnetic field at a frequency that is much smaller compared to conventional ferromagnetic resonance frequency. The scattering of a beam of magnetic nanoparticles in a vacuum in a non-uniform external magnetic field is also considered taking into account the precession of the unit magnetization vector and director.
NASA Astrophysics Data System (ADS)
Dima, G. I.; Kuhn, J. R.; Mickey, D.
2014-12-01
Measuring the coronal vector magnetic field is still a major challenge in solar physics. This is due to the intrinsic weakness of the field (~4 G at a height of 0.1 Rsun above an active region) and the large thermal broadening of coronal emission lines. Current methods deduce either the direction of the magnetic field or the magnetic flux density. We propose using concurrent linear polarization measurements in the near IR of forbidden and permitted lines to calculate the coronal vector magnetic field. The effect of the magnetic field on the polarization properties of emitted light is encapsulated in the Hanle effect. In the unsaturated Hanle regime both the direction and strength of the magnetic field affect the linear polarization, while for saturated Hanle the polarization is insensitive to the strength of the field. Coronal forbidden lines are always in the saturated Hanle regime so the linear polarization holds no information on the strength of the field. By pairing measurements of both forbidden and permitted lines we would be able to obtain both the direction and strength of the field. The near-IR region of the spectrum offers the opportunity to study this problem from the ground. The FeXIII 1.075 um and SiX 1.431 um forbidden lines are strongly polarizable and are sufficiently bright over a large field of view (out to 1.5 Rsun). Measurements of both these lines can be paired up with the recently observed coronal HeI 1.083 um permitted line. The first data set used to test this technique was taken during the March 29, 2006 total solar eclipse and consisted of near-IR spectra covering the spectral region 0.9-1.8 um, with a field of view of 3 x 3 Rsun. The data revealed unexpectedly strong SiX emission compared to FeXIII. Using the HAO FORWARD suite of codes we produced simulated emission maps from a global HMD model for the day of the eclipse. Comparing the intensity variation of the measurements and the model we predict that SiX emission is more extended for this day that the model would suggest, further supporting the possible usefulness of SiX polarimetry. The development of this method and associated tools will be critical in interpreting the high spectral, spatial and temporal IR measurements that will be possible when the Daniel K. Inouye Solar Telescope (DKIST) is completed in a few years time.
Killing Vector Fields and Superharmonic Field Theories
Josua Groeger
2013-01-23
The harmonic action functional allows a natural generalisation to semi-Riemannian supergeometry, referred to as superharmonic action, which resembles the supersymmetric sigma models studied in high energy physics. We show that Killing vector fields are infinitesimal supersymmetries of the superharmonic action and prove three different Noether theorems in this context. En passant, we provide a homogeneous treatment of five characterisations of Killing vector fields on semi-Riemannian supermanifolds, thus filling a gap in the literature.
Elliptic-symmetry vector optical fields.
Pan, Yue; Li, Yongnan; Li, Si-Min; Ren, Zhi-Cheng; Kong, Ling-Jun; Tu, Chenghou; Wang, Hui-Tian
2014-08-11
We present in principle and demonstrate experimentally a new kind of vector fields: elliptic-symmetry vector optical fields. This is a significant development in vector fields, as this breaks the cylindrical symmetry and enriches the family of vector fields. Due to the presence of an additional degrees of freedom, which is the interval between the foci in the elliptic coordinate system, the elliptic-symmetry vector fields are more flexible than the cylindrical vector fields for controlling the spatial structure of polarization and for engineering the focusing fields. The elliptic-symmetry vector fields can find many specific applications from optical trapping to optical machining and so on. PMID:25321015
Vector Fields Resembling Dark Energy
NASA Astrophysics Data System (ADS)
Bretón, Nora
We review how vector fields have been introduced to produce inflationary scenarios in early universes and recently they have been invoked to mimick dark energy. These last approaches have been mostly qualitatives, requiring then to be tested with cosmological probes, in order to seriously be considered as one of the possible causes of the present accelerated expansion of the universe.
NASA Astrophysics Data System (ADS)
Jarvet, Jüri; Allard, Peter; Ehrenberg, Anders; Gräslund, Astrid
The spectral-density mapping of a 13C ?- 1H ?vector of Leu 10in the 22-residue peptide hormone motilin [P. Allard, J. Jarvet, A. Ehrenberg, and A. Gräslund, J. Biomol. NMR5,133-146 (1995)] is extended in this paper to three polarizing fields 9.4, 11.7, and 14.1 T in order to improve the accuracy of the calculated spectral-density function J(?) and to extend the sampling range up to 750 MHz. The problem with a usually large relative error in J(? H) is eliminated since the generally more precise J(? H- ? C) and J(? H+ ? C) determined at other fields appear at nearly the same frequencies. The fitting of dynamic models to the points of spectral density was made with error weighting, and the influence of J(? H) was found to be negligible. Therefore, the high-frequency part of the spectral-density function is determined essentially without influence from the two transverse-type relaxation rates. In the case of a carbon-proton vector, the relaxation is mainly determined by dipolar interaction and is only weakly influenced by other relaxation mechanisms, which makes it particularly suitable for the spectral-density mapping technique. The measured relaxation rates in the time domain are transformed into the frequency domain by spectral-density mapping, and the slopes in different frequency regions are important parameters when comparing experimental data with theoretical models of motion. Using an adjustable internuclear distance reff, combined with the model-free approach, it is possible to obtain a reasonable fit to measured spectral-density points at J(0) and around J(? C). At the same time, however, the high-frequency slope of the spectral-density function defined by J(? H- ? C) and J(? H+ ? C) could not be reproduced.
NASA Astrophysics Data System (ADS)
Hoeksema, Jon T.; HMI Magnetic Field Team
2013-07-01
The Helioseismic and Magnetic Imager (HMI) on SDO has measured magnetic field, velocity, and intensity in the photosphere over the full disk continuously since May 2010 with arc-second resolution. Scalar images are measured every 45 seconds. From these basic observables the pipeline automatically identifies and tracks active regions on the solar disk. The vector magnetic field and a variety of summary quantities are determined every 720s in these tracked Space-weather HMI Active Region Patches (SHARPS). Synoptic and synchronic maps are constructed daily and after each Carrington Rotation Most data products are available with definitive scientific calibration after a few day deal at and in a quick-look near-real-time version a few minutes after the observations are made. Uncertainties are determined for the derived products. All of the magnetic field products along with movies and images suitable for browsing are available at http:://Hmi.stanford.edu/magnetic. Other products, e.g. coronal field over active regions, can be computed on demand.
NASA Astrophysics Data System (ADS)
Hayashi, Keiji; Hoeksema, J. T.; Liu, Y.; Sun, X.; Bobra, M.; Norton, A. A.
2013-07-01
We investigate the dynamics of the solar active regions by means of our data-driven time-dependent three-dimensional MHD simulation model using the HMI vector magnetic field data. The simulations start with pre-emergence phase, or very early phase of the active region so that the development of the loop structures and other signatures of the active regions will be traced. We tested several cases, mainly for AR 11158 of Feb. 2011. Either of the plasma motion or electric field, inferred from the DAVE4VM (Schuck, 2008) is given to the solar-surface boundary surface of the simulation box to which the method of projected normal characteristics (Nakagawa et al. 1987; Wu and Wang, 1987) is applied to ensure the numerical stability and consistency in physics. As our first attempt, we choose the ideal MHD equations without any additional terms except gravity. The results of the simulation show that the method can trace some signatures of the solar active regions, such as development of the magnetic-field loop and (nonlinear) twist. Not having all information at the simulation initial time, nor all physics processes on the photosphere, at transition region, and in the solar corona, agreements in plasma quantities with the other observation such as AIA image data are limited. No flare-like eruptions were obtained under a simulation setting we currently test. The temporal sequences of three-component vector data can give good constraints on the MHD simulation studies of the sub-Alfvenic region, though, we will need more observations, and probably assumptions, to fulfill the physics system. The MHD simulation can be a powerful tool to bridge the measurements and observation, helping interpretation and giving requirement.
Elizabeth A Ainsbury; Emma Conein; Denis L Henshaw
2005-01-01
Elliptically polarized magnetic fields induce higher currents in the body compared with their plane polarized counterparts. This investigation examines the degree of vector ellipticity of extremely low frequency magnetic fields (ELF-MFs) in the home, with regard to the adverse health effects reportedly associated with ELF-MFs, for instance childhood leukaemia. Tri-axial measurements of the magnitude and phase of the 0–3000 Hz
Introduction to Vector Field Visualization
NASA Technical Reports Server (NTRS)
Kao, David; Shen, Han-Wei
2010-01-01
Vector field visualization techniques are essential to help us understand the complex dynamics of flow fields. These can be found in a wide range of applications such as study of flows around an aircraft, the blood flow in our heart chambers, ocean circulation models, and severe weather predictions. The vector fields from these various applications can be visually depicted using a number of techniques such as particle traces and advecting textures. In this tutorial, we present several fundamental algorithms in flow visualization including particle integration, particle tracking in time-dependent flows, and seeding strategies. For flows near surfaces, a wide variety of synthetic texture-based algorithms have been developed to depict near-body flow features. The most common approach is based on the Line Integral Convolution (LIC) algorithm. There also exist extensions of LIC to support more flexible texture generations for 3D flow data. This tutorial reviews these algorithms. Tensor fields are found in several real-world applications and also require the aid of visualization to help users understand their data sets. Examples where one can find tensor fields include mechanics to see how material respond to external forces, civil engineering and geomechanics of roads and bridges, and the study of neural pathway via diffusion tensor imaging. This tutorial will provide an overview of the different tensor field visualization techniques, discuss basic tensor decompositions, and go into detail on glyph based methods, deformation based methods, and streamline based methods. Practical examples will be used when presenting the methods; and applications from some case studies will be used as part of the motivation.
Vector field theories in cosmology
A. Tartaglia; N. Radicella
2007-08-05
Recently proposed theories based on the cosmic presence of a vectorial field are compared and contrasted. In particular the so called Einstein aether theory is discussed in parallel with a recent proposal of a strained space-time theory (Cosmic Defect theory). We show that the latter fits reasonably well the cosmic observed data with only one, or at most two, adjustable parameters, whilst other vector theories use much more. The Newtonian limits are also compared. Finally we show that the CD theory may be considered as a special case of the aether theories, corresponding to a more compact and consistent paradigm.
ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields. Credits: 4 Terms Offered: Fall Prerequisites: MTH 255, ENGR 203 (concurrent enrollment fields in free space, Ampere's circuital law, vector magnetic potential · Biot-Savart law, magnetic
Magnetic fields in astrophysics
Ia. B. Zeldovich; A. A. Ruzmaikin; D. D. Sokolov
1983-01-01
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
Vector fields and multidimensional integrable hierarchies
Fominov, Yakov
Vector fields and multidimensional integrable hierarchies L.V. Bogdanov in collaboration with S on nonlinear vector Riemann problem 3. General (N+2)-dimensional one-point hierarchy Dunajski system hierarchy.D. Landau ITP RAS, Moscow) Zakharov 70 2 / 26 #12;Introduction Linear operators (Lax pairs) Â vector fields
The MAVEN Magnetic Field Investigation
NASA Astrophysics Data System (ADS)
Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.
2015-06-01
The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a resolution of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05 %. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers—multiple rotations about the spacecraft x and z axes—to characterize spacecraft fields and/or instrument offsets in flight.
The MAVEN Magnetic Field Investigation
NASA Technical Reports Server (NTRS)
Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.
2014-01-01
The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.
Exploring Magnetic Field Lines
NSDL National Science Digital Library
NASA
2012-06-26
In this activity, learners explore the magnetic field of a bar magnet as an introduction to understanding Earth's magnetic field. First, learners explore and play with magnets and compasses. Then, learners trace the field lines of the magnet using the compass on a large piece of paper. This activity will also demonstrate why prominences are always "loops."
Helicity of the Solar Magnetic Field
Sanjiv Kumar Tiwari
2009-01-01
Magnetic helicity is a physical quantity that measures the degree of linkages and twistedness in the field lines. It is given by a volume integral over the scalar product of magnetic field B and its vector potential A. Direct computation of magnetic helicity in the solar atmosphere is not possible due to two reasons. First, we do not have the
K. B. Maracas
1994-01-01
Increasing electrification brings increased human exposures to electric and magnetic fields, commonly called EMFs, and growing evidence suggests that exposure to even low frequency, low energy, electric and magnetic fields may be related to adverse health effects. This paper focuses on magnetic fields and strategies that address them. The challenges faced by scientists in understanding magnetic field interactions with humans,
Topology-Preserving Smoothing of Vector Fields
Rüdiger Westermann; Christopher Johnson; Thomas Ertl
2001-01-01
In this paper we propose a technique for topology preserving smoothing of sampled vector fields. The vector field data is first converted into a scalar representation in which time surfaces im- plicitly exist as level-sets. We then locally analyze the dynamic behavior of level-sets by placing geometric primitives in the scalar field and by subsequently distorting these primitives with respect
Ellipsoid flowed around by a harmonic vector field
NASA Astrophysics Data System (ADS)
Savchenko, A. O.; Savchenko, O. Ya.
2012-03-01
We consider the screening of an external magnetic field in which a superconducting ellipsoid is inserted and a change in the velocity distribution in an ideal liquid flowing around an ellipsoid inserted in it. In both cases, the solution is given by a harmonic vector field parallel to the surface near the ellipsoid.
Magnetization strucrure of thermal vent on island arc from vector magnetic anomlies using AUV
NASA Astrophysics Data System (ADS)
Isezaki, N.; Matsuo, J.; Sayanagi, K.
2012-04-01
The geomagnetic anomaly measured by a scalar magnetometer,such as a proton precession magnetometer cannot be defined its direction, then it does not satisfy the Laplace's equation. Therefore physical formula describing the relation between magnetic field and magnetization cannot be established.Because the difference between results obtained from scalar data and from vector data is very significant, we must use vector magnetic field data for magnetization analyses to get the more reliable and exact solutions. The development program of fundamental tools for exploration of deep seabed resources started with the financial support of the Ministry of Education, Culture, Sports, Science & Technology (MEXT) in 2008 and will end in 2012. In this project, we are developing magnetic exploration tools for seabed resources using AUV (Autonomous Underwater Vehicle) and other deep-towed vehicles to measure not the scalar magnetic field but the vector magnetic field in order to estimate magnetization structure below the sea-floor exactly and precisely. We conducted AUV magnetic survey in 2010 at the thermal area called Hakurei deposit in the Bayonnaise submarine caldera at the southern end of Izu island arc, about 400km south of Tokyo. We analyzed the observed vector magnetic fields to get the vector magnetic anomaly Fields using the method of Isezaki(1984). We inverted these vector magnetic anomaly fields to magnetization structure. CONCLUSIONS 1.The scalar magnetic field TIA (Total Intensity Anomaly) has no physical formula describing the relation between M (Magnetization) and TIA because TIA does not satisfy the Laplace's equation. Then it is impossible to estimate M from TIA. 2.Anlyses of M using TIA have been done so far under assumption TIA=PTA (Projected Total Anomay on MF (Main Geomagnetic Field)), however, which caused the analysis error due to ?T= TIA - PTA . 3.We succeeded to measure the vector magnetic anomaly fields using AUV despite the severe magnetic noises around the magnetometer sensors. The method of Isezaki(1984) works good to eliminate these noises. 4.We got the very precise magnetization structure in the Bayonnaise submarine caldera area at the southern end of Izu island arc. We used the prism model which forms the shape of magnetized source body whose top is the sea-floor. The total number od prisms is 1500 making the 3 layers (0-80m, 80-160m, 160- 240m below the sea-floor, 25x20=500 prisms in 1 layer). The 4500 unknowns(3 unknowns, Mx,My,Mz in each prosm) are obtained from 12000 observed vector magnetic anomaly fields by inversion method. 5. The tentative result shows that the 1st and 2nd layers have smaller intensity of magnetization compared to the 3rd layer. The 2nd layer has the smallest of three layers. However the Hakurei deposit area in the 2nd layer has the a little bit greater magnetization than surrounding area which suggests that the Hakurei deposit includes some magnetic minerals. 6.We strongly recommend to carry out the magnetic survey using a three component magnetometer to get TF and TA which have many advantages for magnetic analyses (magnetization, upward continuation etc.) which cannot be done using scalar TIA.
NSDL National Science Digital Library
2014-09-18
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.
NSDL National Science Digital Library
In this activity, students investigate the presence of magnetic fields around magnets, the sun and the earth. They will explore magnetic field lines, understand that magnetic lines of force show the strength and direction of magnetic fields, determine how field lines interact between attracting and repelling magnetic poles, and discover that the earth and sun have magnetic properties. They will also discover that magnetic force is invisible and that a "field of force" is a region or space in which one object can attract or repel another.
Seong Deok Kong
2010-01-01
Hollow-sphere nanocapsules containing intentionally trapped magnetic nanoparticles and defined anticancer drugs provide a powerful magnetic vector under moderate gradient magnetic fields, and enable the nanocapsules to penetrate into the midst of tumors and allow a controlled on-off switchable release of the anticancer drug cargo by remotely applied Radio Frequency (RF) magnetic field. This imageable smart drug delivery system is compact
Preflare magnetic and velocity fields
NASA Technical Reports Server (NTRS)
Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.
1986-01-01
A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares
NSDL National Science Digital Library
2012-08-03
This is an activity about magnetic fields. Using iron filings, learners will observe magnets in various arrangements to investigate the magnetic field lines of force. This information is then related to magnetic loops on the Sun's surface and the magnetic field of the Earth. This is the second activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.
Visualizing Magnetic Field Lines
NSDL National Science Digital Library
2014-09-18
In this activity, students take the age old concept of etch-a-sketch a step further. Using iron filings, students begin visualizing magnetic field lines. To do so, students use a compass to read the direction of the magnet's magnetic field. Then, students observe the behavior of iron filings near that magnet as they rotate the filings about the magnet. Finally, students study the behavior of iron filings suspended in mineral oil which displays the magnetic field in three dimensions.
Faraday's law via the magnetic vector potential
Dragan V Redži?
2007-01-01
Faraday's law for a filamentary circuit which is moving at relativistic velocities and also changing its shape as it moves is derived via the magnetic vector potential. The derivation is simpler than the usual one, based on the Hertz–Helmholtz identity.
Aleksandr A. Ruzmaikin; Dmitrii D. Sokolov; Anvar M. Shukurov
1988-01-01
The current state of the understanding of the magnetic fields of galaxies is reviewed. A simple model of the turbulent dynamo is developed which explains the main observational features of the global magnetic fields of spiral galaxies. The generation of small-scale chaotic magnetic fields in the interstellar medium is also examined. Attention is also given to the role of magnetic
Multi-task Vector Field Learning
Lin, Binbin; Yang, Sen; Zhang, Chiyuan; Ye, Jieping; He, Xiaofei
2013-01-01
Multi-task learning (MTL) aims to improve generalization performance by learning multiple related tasks simultaneously and identifying the shared information among tasks. Most of existing MTL methods focus on learning linear models under the supervised setting. We propose a novel semi-supervised and nonlinear approach for MTL using vector fields. A vector field is a smooth mapping from the manifold to the tangent spaces which can be viewed as a directional derivative of functions on the manifold. We argue that vector fields provide a natural way to exploit the geometric structure of data as well as the shared differential structure of tasks, both of which are crucial for semi-supervised multi-task learning. In this paper, we develop multi-task vector field learning (MTVFL) which learns the predictor functions and the vector fields simultaneously. MTVFL has the following key properties. (1) The vector fields MTVFL learns are close to the gradient fields of the predictor functions. (2) Within each task, the vector field is required to be as parallel as possible which is expected to span a low dimensional subspace. (3) The vector fields from all tasks share a low dimensional subspace. We formalize our idea in a regularization framework and also provide a convex relaxation method to solve the original non-convex problem. The experimental results on synthetic and real data demonstrate the effectiveness of our proposed approach. PMID:25332642
Visualizing vector field topology in fluid flows
James L. Helman; Lambertus Hesselink
1991-01-01
Methods for automating the analysis and display of vector field topology in general, and flow topology in particular, are described. By using techniques to extract and visualize topological information, it is possible to combine the simplicity of schematic depictions with the quantitative accuracy of curves and surfaces computed directly from the data. Two-dimensional vector field topology is discussed, covering critical
Vector fields on $?$-symmetric flag supermanifolds
E. G. Vishnyakova
2015-06-07
The main result of this paper is the computation of the Lie superalgebras of holomorphic vector fields on the complex $\\Pi$-symmetric flag supermanifolds, introduced by Yu.I.~Manin. We prove that with one exception any vector field is fundamental with respect to the natural action of the Lie superalgebra $\\mathfrak q_n(\\mathbb C)$.
Imaging vector fields using line integral convolution
Brian Cabral; Leith Casey Leedom
1993-01-01
Imaging vector fields has applications in science, art, image pro- cessing and special effects. An effective new approach is to use linear and curvilinear filtering techniques to locally blur textures along a vector field. This approach builds on several previous tex- ture generation and filtering techniques(8, 9, 11, 14, 15, 17, 23). It is, however, unique because it is local,
Magnetic field spectrum at cosmological recombination revisited
NASA Astrophysics Data System (ADS)
Saga, Shohei; Ichiki, Kiyotomo; Takahashi, Keitaro; Sugiyama, Naoshi
2015-06-01
If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, nonlinear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-terms of the first-order scalar modes, in the tight coupling regime in the radiation dominated era. Therefore, the amplitude of the magnetic fields on small scales, k ?10 h Mpc-1 , is smaller than the previous estimates. The amplitude of the generated magnetic fields at cosmological recombination is about Brec=5.0 ×10-24 Gauss on k =5.0 ×10-1 h Mpc-1 . Finally, we discuss the reason for the discrepancies that exist in estimates of the amplitude of magnetic fields among other authors.
Critical collapse of a massive vector field
David Garfinkle; Robert Mann; Chris Vuille
2003-05-03
We perform numerical simulations of the critical gravitational collapse of a massive vector field. The result is that there are two critical solutions. One is equivalent to the Choptuik critical solution for a massless scalar field. The other is periodic.
Clifford Fourier transform on vector fields.
Ebling, Julia; Scheuermann, Gerik
2005-01-01
Image processing and computer vision have robust methods for feature extraction and the computation of derivatives of scalar fields. Furthermore, interpolation and the effects of applying a filter can be analyzed in detail and can be advantages when applying these methods to vector fields to obtain a solid theoretical basis for feature extraction. We recently introduced the Clifford convolution, which is an extension of the classical convolution on scalar fields and provides a unified notation for the convolution of scalar and vector fields. It has attractive geometric properties that allow pattern matching on vector fields. In image processing, the convolution and the Fourier transform operators are closely related by the convolution theorem and, in this paper, we extend the Fourier transform to include general elements of Clifford Algebra, called multivectors, including scalars and vectors. The resulting convolution and derivative theorems are extensions of those for convolution and the Fourier transform on scalar fields. The Clifford Fourier transform allows a frequency analysis of vector fields and the behavior of vector-valued filters. In frequency space, vectors are transformed into general multivectors of the Clifford Algebra. Many basic vector-valued patterns, such as source, sink, saddle points, and potential vortices, can be described by a few multivectors in frequency space. PMID:16138556
Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance Three Axis Vector Magnetometer
NASA Astrophysics Data System (ADS)
Bulatowicz, Michael; Clark, Philip; Griffith, Robert; Larsen, Michael; Mirijanian, James
2012-06-01
The Northrop Grumman Corporation is leveraging the technology developed for the Nuclear Magnetic Resonance Gyroscope (NMRG) to build a combined Electron Paramagnetic Resonance -- Nuclear Magnetic Resonance (EPR-NMR) magnetometer. The EPR-NMR approach provides a high bandwidth and high sensitivity simultaneous measurement of all three vector components of the magnetic field averaged over the small volume of the sensor's one vapor cell. This poster will describe the history, operational principles, and design basics of the EPR-NMR magnetometer including an overview of the NSD designs developed and demonstrated to date. General performance results will also be presented.
Facility Measures Magnetic Fields
NASA Technical Reports Server (NTRS)
Honess, Shawn B.; Narvaez, Pablo; Mcauley, James M.
1991-01-01
Partly automated facility measures and computes steady near magnetic field produced by object. Designed to determine magnetic fields of equipment to be installed on spacecraft including sensitive magnetometers, with view toward application of compensating fields to reduce interfernece with spacecraft-magnetometer readings. Because of its convenient operating features and sensitivity of its measurements, facility serves as prototype for similar facilities devoted to magnetic characterization of medical equipment, magnets for high-energy particle accelerators, and magnetic materials.
Vector fields and Loop Quantum Cosmology
Artymowski, Micha?; Lalak, Zygmunt, E-mail: Michal.Artymowski@fuw.edu.pl, E-mail: Zygmunt.Lalak@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Ho?a 69, 00-681 Warszawa (Poland)
2011-09-01
In the context of the Loop Quantum Cosmology we have analysed the holonomy correction to the classical evolution of the simplified Bianchi I model in the presence of vector fields. For the Universe dominated by a massive vector field or by a combination of a scalar field and a vector field a smooth transition between Kasner-like and Kasner-unlike solutions for a Bianchi I model has been demonstrated. In this case a lack of initial curvature singularity and a finite maximal energy density appear already at the level of General Relativity, which simulates a classical Big Bounce.
NSDL National Science Digital Library
2012-08-03
This is an activity about the declining strength of Earth's magnetic field. Learners will review a graph of magnetic field intensity and calculate the amount by which the field has changed its intensity in the last century, the rate of change of its intensity, and when the field should decrease to zero strength at the current rate of change. Learners will also use evidence from relevant sources to create a conjecture on the effects on Earth of a vanished magnetic field. Access to information sources about Earth's magnetic field strength is needed for this activity. This is Activity 7 in the Exploring Magnetism on Earth teachers guide.
Magsat vector magnetometer calibration using Magsat geomagnetic field measurements
NASA Technical Reports Server (NTRS)
Lancaster, E. R.; Jennings, T.; Morrissey, M.; Langel, R. A.
1980-01-01
From the time of its launch on Oct. 30, 1979 into a nearly polar, Sun synchronous orbit, until it reentered the Earth's atmosphere on June 11, 1980, Magsat measured and transmitted more than three complete sets of global magnetic field data. The data obtained from the mission will be used primarily to compute a currently accurate model of the Earth's main magnetic field, to update and refine world and regional magnetic charts, and to develop a global scalar and vector crustal magnetic anomaly map. The in-flight calibration procecure used for 39 vector magnetometer system parameters is described as well as results obtained from some data sets and the numerical studies designed to evaluate the results.
Recurrent structures of the interplanetary magnetic field observed by ULYSSES
G. Erdos; A. Balogh; R. J. Forsyth; E. J. Smith
1995-01-01
Since its launch in October 1990, Ulysses has provided good quality magnetic field data, practically covering the whole time interval until now. We have studied the very long time scale evolution of the interplanetary magnetic field, in particlular, we have search for recurrent disturbances in the magnetic field. The magnetic field vectors have been mapped back to the Sun along
Magnetic Fields Analogous to electric field, a magnet
Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University
Magnetic Fields Analogous to electric field, a magnet produces a magnetic field, B Set up a B field two ways: Moving electrically charged particles Current in a wire Intrinsic magnetic field Basic characteristic of elementary particles such as an electron #12;Magnetic Fields Magnetic field lines Direction
Magnetic field observations in Comet Halley's coma
NASA Astrophysics Data System (ADS)
Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.
1986-05-01
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.
Magnetic Gradiometer and Vector Magnetometer Survey of the Eastern Mediterranean
NASA Astrophysics Data System (ADS)
Granot, R.
2014-12-01
Some of the fundamental tectonic problems of the Eastern Mediterranean remain unresolved due to the extremely thick sedimentary cover (~15 km) and the lack of accurate magnetic anomaly data. We conducted a magnetic survey of the Herodotus and Levant Basins (Eastern Mediterranean) to study the nature and age of the underlying igneous crust. The towed magnetometer array consisted of two Overhauser sensors recording the total magnetic field in a longitudinal gradiometer mode, and a marine vector magnetometer. Accurate navigation together with the gradiometer data allows the separation of the magnetic signature of the lithosphere from the contributions of the external magnetic field and the geomagnetic field. Total field data in the Herodotus Basin reveal a sequence of long-wavelength NE-SW lineated anomalies (~80 nT) suggesting a deep (~20 km) 2D magnetic source layer. Analysis of the vector data shows a steady azimuth of lineations that is generally consistent with the total field anomalies. The sequence of anomalies is rather short and does not allow a unique identification. However, the continuous northward motion of the African Plate during the Paleozoic and Mesozoic result in predictable anomaly skewness patterns for the different time periods. Forward magnetic modeling best fit the observed anomalies when using Early Permian remanence directions. Altogether, these observations and analysis suggest that a Neo-Tethyan Permian oceanic crust underlies the Herodotus Basin. Two short-wavelengths and strong (~400 nT) anomalies are found in the Levant Basin, proposing rather shallow (~7 km) magnetic sources there. These anomalies spatially coincide with Mesozoic uplifted continental structures (Eratosthenes and Jonah Highs).
NSDL National Science Digital Library
Jeffrey Barker
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.
Electricity and Magnetic Fields
NSDL National Science Digital Library
VU Bioengineering RET Program,
The grand challenge for this legacy cycle unit is for students to design a way to help a recycler separate aluminum from steel scrap metal. In previous lessons, they have looked at how magnetism might be utilized. In this lesson, students think about how they might use magnets and how they might confront the problem of turning the magnetic field off. Through the accompanying activity students explore the nature of an electrically induced magnetic field and its applicability to the needed magnet.
NSDL National Science Digital Library
VU Bioengineering RET Program,
Students use a compass and a permanent magnet to trace the magnetic field lines produced by the magnet. By positioning the compass in enough spots around the magnet, the overall magnet field will be evident from the collection of arrows representing the direction of the compass needle. In activities 3 and 4 of this unit, students will use this information to design a way to solve the grand challenge of separating metal for a recycling company.
NSDL National Science Digital Library
VU Bioengineering RET Program,
Students use the same method as in the activity from lesson 2 of this unit to explore the magnetism due to electric current instead of a permanent magnet. Students use a compass and circuit to trace the magnetic field lines induced by the electric current moving through the wire. Students develop an understanding of the effect of the electrical current on the compass needle through the induced magnetic field and understand the complexity of a three dimensional field system.
N. F. Ness; M. H. Acuna; L. F. Burlaga; J. E. P. Connerney; R. P. Lepping; F. M. Neubauer
1989-01-01
The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10â»âµ gauss) was observed near closest approach, at a
Plane fields related to vector fields on 3-manifolds
Clodoaldo Grotta Ragazzo
2004-01-01
This paper is a small collection of results about the topology of non-singular plane fields which are either transverse or\\u000a tangent to nonsingular volume preserving vector fields on 3-manifolds. Emphasis is given to contact plane distributions and\\u000a to restrictions of Hamiltonian vector fields to hypersurfaces in symplectic 4-manifolds.
Killing vector fields and harmonic superfield theories
Groeger, Josua, E-mail: groegerj@mathematik.hu-berlin.de [Humboldt-Universität zu Berlin, Institut für Mathematik, Rudower Chaussee 25, 12489 Berlin (Germany)
2014-09-15
The harmonic action functional allows a natural generalisation to semi-Riemannian supergeometry, also referred to as harmonic, which resembles the supersymmetric sigma models studied in high energy physics. We show that Killing vector fields are infinitesimal supersymmetries of this harmonic action and prove three different Noether theorems in this context. En passant, we provide a homogeneous treatment of five characterisations of Killing vector fields on semi-Riemannian supermanifolds, thus filling a gap in the literature.
NASA Technical Reports Server (NTRS)
Howard, R.
1972-01-01
Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.
NSDL National Science Digital Library
Wolfgang Christian
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.
Magnetic vectoring of magnetically responsive nanoparticles within the murine peritoneum
NASA Astrophysics Data System (ADS)
Klostergaard, Jim; Bankson, James; Auzenne, Edmond; Gibson, Don; Yuill, William; Seeney, Charles E.
2007-04-01
Magnetically responsive nanoparticles (MNPs) might be candidates for pro-drug formulations for intraperitoneal (i.p.) treatment of ovarian cancer. We conducted feasibility experiments in an i.p. human ovarian carcinoma xenograft model to determine whether MNPs can be effectively vectored within this environment. Our initial results based on magnetic resonance imaging (MRI) indicate that i.p.-injected ˜15 nm magnetite-based MNPs can in fact migrate toward NdFeB magnets externally juxtaposed to the peritoneal cavity above the xenografts growing in the anterior abdominal wall. MNP localization to the tumor/peri-tumoral environment occurs. Further development of this MNP pro-drug strategy is underway.
NSDL National Science Digital Library
This is a lesson about the magnetic field of a bar magnet. The lesson begins with an introductory discussion with learners about magnetism to draw out any misconceptions that may be in their minds. Then, learners freely experiment with bar magnets and various materials, such as paper clips, rulers, copper or aluminum wire, and pencils, to discover that magnets attract metals containing iron, nickel, and/or cobalt but not most other materials. Next, learners experiment with using a magnetic compass to discover how it is affected by the magnet and then draw the magnetic field lines of the magnet by putting dots at the location of the compass arrow. This is the first lesson in the first session of the Exploring Magnetism teacher guide.
NSDL National Science Digital Library
Windows to the Universe
1997-12-03
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.
Magnetic Field Problem: Mesuring Current in Wire
NSDL National Science Digital Library
Wolfgang Christian
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.
Hamiltonian Vector Fields on Multiphase Spaces of Classical Field Theory
Michael Forger; Mário Otávio Salles
2010-10-02
We present a classification of hamiltonian vector fields on multisymplectic and polysymplectic fiber bundles closely analogous to the one known for the corresponding dual jet bundles that appear in the multisymplectic and polysymplectic approach to first order classical field theories.
Melatonin and magnetic fields.
Karasek, Michal; Lerchl, Alexander
2002-04-01
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
Vector boson mass generation without new fields.
Berg, Bernd A
2012-06-01
Previously a model of only vector fields with a local U(1)?SU(2) symmetry was introduced for which one finds a massless U(1) photon and a massive SU(2) vector boson in the lattice regularization. Here it is shown that quantization of its classical continuum action leads to perturbative renormalization difficulties. But, nonperturbative Monte Carlo calculations favor the existence of a quantum continuum limit. PMID:23003586
Vector boson mass generation without new fields
Bernd A. Berg
2012-04-21
Previously a model of only vector fields with a local U(2) symmetry was introduced for which one finds a massless U(1) photon and a massive SU(2) vector boson in the lattice regularization. Here it is shown that quantization of its classical continuum action leads to perturbative renormalization difficulties. But, non-perturbative Monte Carlo calculations favor the existence of a quantum continuum limit.
Dunin-Borkowski, Rafal E.
microscope (TEM) [2]. The phase shift is, in turn, sensitive to the in-plane component of the magnetic flux: Illustration of the design of lithographically patterned magnetic elements that can be tilted to high angles of magnetic vector fields in nanoscale materials Diehle P.1 , Caron J.1 , Kovacs A.1 , Ungermann J.2
NASA Astrophysics Data System (ADS)
Kanim, Stephen; Thompson, John R.
2005-09-01
For some years now laminated cards containing a green, magnetically sensitive film have been available from science education suppliers. When held near a magnet, these cards appear dark green in regions where the field is perpendicular to the card and light green where the field is parallel to the card. The cards can be used to explore the magnetic field near a variety of magnets as well as near wire loops. In this paper we describe how to make these cards and how we have used them in our physics classrooms and labs.
Magnetic field line Hamiltonian
Boozer, A.H.
1984-03-01
The magnetic field line Hamiltonian and the associated canonical form for the magnetic field are important concepts both for understanding toroidal plasma physics and for practical calculations. A number of important properties of the canonical or Hamiltonian representation are derived and their importance is explained.
Elisabete M. de Gouveia Dal Pino; Dal Pino
2006-01-01
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
Damping of cosmic magnetic fields
Jedamzik, K. [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany)] [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany); Katalinic, V.; Olinto, A.V. [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)] [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)
1998-03-01
We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic and non-relativistic fast and slow magnetosonic and Alfv{acute e}n waves in the presence of viscous and heat conducting processes. The analysis covers all magnetohydrodynamics modes in the radiation diffusion and the free-streaming regimes. When our results are applied to the evolution of magnetic fields in the early universe, we find that cosmic magnetic fields are damped from prior to the epoch of neutrino decoupling up to recombination. Similar to the case of sound waves propagating in a demagnetized plasma, fast magnetosonic waves are damped by radiation diffusion on all scales smaller than the radiation diffusion length. The characteristic damping scales are the horizon scale at neutrino decoupling (M{sub {nu}}{approx}10{sup {minus}4}M{sub {circle_dot}} in baryons) and the Silk mass at recombination (M{sub {gamma}}{approx}10{sup 13}M{sub {circle_dot}} in baryons). In contrast, the oscillations of slow magnetosonic and Alfv{acute e}n waves get overdamped in the radiation diffusion regime, resulting in frozen-in magnetic field perturbations. Further damping of these perturbations is possible only if before recombination the wave enters a regime in which radiation free-streams on the scale of the perturbation. The maximum damping scale of slow magnetosonic and Alfv{acute e}n modes is always smaller than or equal to the damping scale of fast magnetosonic waves, and depends on the magnetic field strength and its direction relative to the wave vector. Our findings have multifold implications for cosmology. The dissipation of magnetic field energy into heat during the epoch of neutrino decoupling ensures that most magnetic field configurations generated in the very early universe satisfy big bang nucleosynthesis constraints. Further dissipation before recombination constrains models in which primordial magnetic fields give rise to galactic magnetic fields or density perturbations. Finally, the survival of Alfv{acute e}n and slow magnetosonic modes on scales well below the Silk mass may be of significance for the formation of structure on small scales. {copyright} {ital 1998} {ital The American Physical Society}
Magnetic Fields Classroom Activity
NSDL National Science Digital Library
Reinhart, Rose
In this lesson from Math Machines, students will learn about the effects of magnetic fields on moving, electrically charged particles. The activity consists of two exercises. The first involves analyzing how a robot is controlled in a magnetic field. The second has students design and test a "magnetic bottle."A participant handout (including worksheets) and facilitator notes are made available for download in DOC file format. A link to a required calculator program is also provided.
NASA Astrophysics Data System (ADS)
Beck, Rainer
Magnetic fields are a major agent in the interstellar medium. They contribute significantly to the total pressure which balances the gas disk against gravitation. They affect the gas flows in spiral arms (Gómez and Cox, 2002). The effective sound speed of the gas is increased by the presence of strong fields which reduce the shock strength. The interstellar fields are closely connected to gas clouds. They affect the dynamics of the gas clouds (Elmegreen, 1981; de Avillez and Breitschwerdt, 2004). The stability and evolution of gas clouds are also influenced by magnetic fields, but it is not understood how (Crutcher, 1999; see Chap. 7). Magnetic fields are essential for the onset of star formation as they enable the removal of angular momentum from the protostellar cloud during its collapse (magnetic braking, Mouschovias, 1990). Strong fields may shift the stellar mass spectrum towards the more massive stars (Mestel, 1990). MHD turbulence distributes energy from supernova explosions within the ISM (Subramanian, 1998) and regenerates the field via the dynamo process (Wielebinski, R., Krause, 1993, Beck et al., 1996; Sect. 6). Magnetic reconnection is a possible heating source for the ISM and halo gas (Birk et al., 1998). Magnetic fields also control the density and distribution of cosmic rays in the ISM. A realistic model for any process in the ISM needs basic information about the magnetic field which has to be provided by observations.
Interplanetary Magnetic Field Lines
NSDL National Science Digital Library
Mendez, J.
This web page, authored and curated by David P. Stern, provides information and a graphical exercise for students regarding the interaction between magnetic field lines and a plasma. The activity involves tracing a typical interplanetary magnetic field line, dragged out of a location on the Sun by the radial flow of the solar wind. This illustrates the way magnetic field lines are "frozen to the plasma" and the wrapping of field lines due to the rotation of the sun. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.
NASA Technical Reports Server (NTRS)
Hoeksema, J. T.; Suess, S. T.
1990-01-01
The magnetic field of the sun extends outward through the photosphere into the corona. The resulting coronal and interplanetary magnetic fields therefore respond to and evolve with the solar cycle, as well as on shorter and longer time scales. These fields are modeled using photospheric magnetic field observations under the assumption that the coronal field is current free, becomes radial at a 'source surface' placed at 2.5 solar radii from the center of the sun, and is passively advected by the solar wind beyond the source surface. This review covers the computation of such models and their applications to characterize the morphology, evolution, and rotation of coronal and interplanetary magnetic fields using data collected between 1976 and the present at the Wilcox Solar Observatory.
Vector Preisach modeling of magnetic materials under stress
NASA Astrophysics Data System (ADS)
Ktena, A.
2015-02-01
The Preisach formalism is used to model magnetic hysteresis loops in soft magnetic materials subject to tensile stress. The model uses the Stoner-Wohlfarth mechanism of coherent rotation and dispersion of easy axes to capture the vector response of the magnetization. The Preisach density is constructed as the weighed sum of normal probability density functions (pdf) for the regions of high and low induction. The model parameters reflect the effect of strain: increased pinning, modelled by the central pdf parameters; enhanced anisotropy dispersion modelled by the angular dispersion of easy axes. Upon removal of the tensile stress, compressive residual stresses give rise to effective demagnetizing fields leading to lower differential permeability with a two-peak profile. As deformation levels increase, the amplitude of and the relative distance between the two permeability peaks changes which is reflected in the side density parameters. Modelling results are in qualitative agreement with the experimental data. The potential and limitations of the model are discussed.
Vector Field Editing and Periodic Orbit Extraction Using Morse Decomposition
Chen, Guoning
1 Vector Field Editing and Periodic Orbit Extraction Using Morse Decomposition Guoning Chen of vector fields is critical for many visualization and graphics tasks such as vector field visual- ization, fluid simulation, and texture synthesis. The fundamental qualitative structures associated with vector
Constrained motion control using vector potential fields
Samer A. Masoud; Ahmad A. Masoud
2000-01-01
This paper discusses the generation of a control signalthat would instruct the actuators of a robotics manipulator to drivemotion along a safe and well-behaved path to a desired target. Theproposed concept of navigation control along with the tools necessaryfor its construction achieve this goal. The most significant toolis the artificial vector potential field which shows a better ability tosteer motion
Averages in vector spaces over finite fields
Wright J.; Carbery A.; Stones B.
2008-01-01
We study the analogues of the problems of averages and maximal averages over a surface in R-n when the euclidean structure is replaced by that of a vector space over a finite field, and obtain optimal results in a number ...
Hessian structures, Euler vector fields, and thermodynamics
M. Á. García-Ariza
2015-03-02
In this paper, a geometric structure which generalizes that of thermodynamics is presented; spaces of equilibrium states are portrayed as a particular case of the former. For this end, concepts like Euler vector field and extensive function, which are usual in thermodynamics, are introduced in a wider context.
Lorentz and "apparent" transformations of the electric and magnetic fields
Tomislav Ivezic
2006-07-21
It is recently discovered that the usual transformations of the three-dimensional (3D) vectors of the electric and magnetic fields differ from the Lorentz transformations (LT) (boosts) of the corresponding 4D quantities that represent the electric and magnetic fields. In this paper, using geometric algebra formalism, this fundamental difference is examined representing the electric and magnetic fields by bivectors.
Visualization of Vector Fields in Quantum Chemistry
Detlev Stalling; Thomas Steinke
1996-01-01
Many interesting phenomena in molecular systems like interactions between macromolecules,protein-substrate docking, or channeling processes in membranes aregouverned to a high degree by classical Coulomb or van-der-Waals forces. Thevisualization of these force fields is important for verifying numerical simulations.Moreover, by inspecting the forces visually we can gain deeper insight into themolecular processes. Up to now the visualization of vector fields is
''Massless'' vector field in de Sitter universe
Garidi, T.; Gazeau, J.-P. [APC, CNRS UMR 7164, Universite Paris Diderot Paris 7, F-75205 Paris Cedex 13 (France); Rouhani, S. [Plasma Physics Research Center, Islamic Azad University, P.O. Box 14835-157, Tehran (Iran, Islamic Republic of); Takook, M. V. [Department of Physics, Razi University, P. O. Box 67155, Kermanshah (Iran, Islamic Republic of)
2008-03-15
We proceed to the quantization of the massless vector field in the de Sitter (dS) space. This work is the natural continuation of a previous article devoted to the quantization of the dS massive vector field [J. P. Gazeau and M. V. Takook, J. Math. Phys. 41, 5920 (2000); T. Garidi et al., ibid. 43, 6379 (2002).] The term ''massless'' is used by reference to conformal invariance and propagation on the dS lightcone whereas ''massive'' refers to those dS fields which unambiguously contract to Minkowskian massive fields at zero curvature. Due to the combined occurrences of gauge invariance and indefinite metric, the covariant quantization of the massless vector field requires an indecomposable representation of the de Sitter group. We work with the gauge fixing corresponding to the simplest Gupta-Bleuler structure. The field operator is defined with the help of coordinate-independent de Sitter waves (the modes). The latter are simple to manipulate and most adapted to group theoretical approaches. The physical states characterized by the divergencelessness condition are, for instance, easy to identify. The whole construction is based on analyticity requirements in the complexified pseudo-Riemannian manifold for the modes and the two-point function.
Magnetic fields in spiral galaxies
NASA Astrophysics Data System (ADS)
Chiba, Masashi
The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.
Detecting Exoplanetary Magnetic Fields
NASA Astrophysics Data System (ADS)
Llama, Joe
2015-01-01
Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System.Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet's magnetic field with the stellar wind from it's host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets.The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star's magnetic field.In this presentation I will show modelling a bow shock around an exoplanet can help us to not only detect, but also also place constraints on the magnetic field strength of hot Jupiters. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. I will also show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.
NSDL National Science Digital Library
This is an activity about electromagnetism. Learners will use a compass to map the magnetic field lines surrounding a coil of wire that is connected to a battery. This activity requires a large coil or spool of wire, a source of electricity such as 3 D-cell batteries or an AC to DC power adapter, alligator-clipped wire, and magnetic compasses. This is the third lesson in the second session of the Exploring Magnetism teachers guide.
Wavelet Transforms for Vector Fields Using Omnidirectionally Balanced Multiwavelets
Fowler, James E.
Wavelet Transforms for Vector Fields Using Omnidirectionally Balanced Multiwavelets James E. Fowler, Senior Member, IEEE, and Li Hua, Student Member, IEEE Abstract--Vector wavelet transforms for vector implementation of a vector wavelet transform, namely the application of a scalar transform to each vector
Improved determination of vector lithospheric magnetic anomalies from MAGSAT data
NASA Technical Reports Server (NTRS)
Ravat, Dhananjay
1993-01-01
Scientific contributions made in developing new methods to isolate and map vector magnetic anomalies from measurements made by Magsat are described. In addition to the objective of the proposal, the isolation and mapping of equatorial vector lithospheric Magsat anomalies, isolation of polar ionospheric fields during the period were also studied. Significant progress was also made in isolation of polar delta(Z) component and scalar anomalies as well as integration and synthesis of various techniques of removing equatorial and polar ionospheric effects. The significant contributions of this research are: (1) development of empirical/analytical techniques in modeling ionospheric fields in Magsat data and their removal from uncorrected anomalies to obtain better estimates of lithospheric anomalies (this task was accomplished for equatorial delta(X), delta(Z), and delta(B) component and polar delta(Z) and delta(B) component measurements; (2) integration of important processing techniques developed during the last decade with the newly developed technologies of ionospheric field modeling into an optimum processing scheme; and (3) implementation of the above processing scheme to map the most robust magnetic anomalies of the lithosphere (components as well as scalar).
Magnetic field dosimeter development
Lemon, D.K.; Skorpik, J.R.; Eick, J.L.
1980-09-01
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.
How the geomagnetic field vector reverses polarity
Prevot, M.; Mankinen, E.A.; Gromme, C.S.; Coe, R.S.
1985-01-01
A highly detailed record of both the direction and intensity of the Earth's magnetic field as it reverses has been obtained from a Miocene volcanic sequence. The transitional field is low in intensity and is typically non-axisymmetric. Geomagnetic impulses corresponding to astonishingly high rates of change of the field sometimes occur, suggesting that liquid velocity within the Earth's core increases during geomagnetic reversals. ?? 1985 Nature Publishing Group.
George, Glyn
ENGI 5432 1. Vector Fields and the Gradient Operator Page 1-01 1. Vector Fields and the Gradient Operator In this chapter, a review of vectors from previous courses is followed by the introduction and general orthonormal curvilinear coordinate systems. Conversion of components of vectors between Cartesian
Magnetic Field Problem: Current
NSDL National Science Digital Library
Wolfgang Christian
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.
Intermittent Vector Fields: A Challenge for Mathematical Geophysics?
NASA Astrophysics Data System (ADS)
Schertzer, D. J. M.; Tchiguirinskaia, I.
2014-12-01
Geophysical fields display strong intermittency over a wide range of scales. Multifractals has become a standard tool to analyze and simulate this key phenomenon for scalar fields. However, fields of interest, e.g. the velocity and the magnetic fields are vector fields. Some time ago, "Lie cascades" were introduced to deal with such fields by considering exponentiation from a stochastic element of a Lie algebra to its corresponding Lie group of transformations. The concerned transformation corresponds to the fine graining/downscaling of the field to higher and higher resolution. Unfortunately, developments were paused due to the possible large number of degrees of freedom of the latter, in particular with respect to the information that can be easily extracted from a d-dimensional vector field. In short, some physics was missing. In this communication, we point out the interest of the Clifford algebra Clp,q to make concrete progress. Ironically, these algebra were mentioned at once as rather straightforward generalizations of the scalar complex cascades, but they were not investigated. On the contrary, the particular case of the "pseudo-quaternions" l(2,R)=Cl2,0=Cl1,1 has been often used to generate generalized scales to analyse and simulate anistropic scaling (scalar) fields. The latter is in fact illustrative of the basic property of the Clifford algebra Clp,q to be generated by a quadratic form Q whose signature (p,q) is fundamental.
CMB non-gaussianity from vector fields
Peloso, Marco [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)
2014-01-01
The Planck satellite has recently measured the CMB temperature anisotropies with unprecedented accuracy, and it has provided strong bounds on primordial non-gaussianity. Such bounds constrain models of inflation, and mechanisms that produce the primordial perturbations. We discuss the non-gaussian signatures from the interactions of the inflation ? with spin-1 fields. We study the two different cases in which the inflaton is (i) a pseudo-scalar field with a (?)/(fa) F·F interaction with a vector field, and (ii) a scalar field with a f (?)F² interaction. In the first case we obtain the strong limit f{sub a} ? 10¹?GeV on the decay constant. In the second case, specific choices of the function f (?) can lead to a non-gaussianity with a characteristic shape not encountered in standard models of scalar field inflation, and which has also been constrained by Planck.
Decay of Resonaces in Strong Magnetic Field
Peter Filip
2015-04-27
We suggest that decay properties (branching ratios) of hadronic resonances may become modified in strong external magnetic field. The behavior of $K^{\\pm *}\\!$, $K^{0*}$ vector mesons as well as $\\Lambda^*(1520)$ and $\\Xi^{0*}$ baryonic states is considered in static fields $10^{13}$-\\,$10^{15}$ T. In particular, $n=0$ Landau level energy increase of charged particles in the external magnetic field, and the interaction of hadron magnetic moments with the field is taken into account. We suggest that enhanced yield of dileptons and photons from $\\rho^0(770)$ mesons may occur if strong decay channel $\\rho^0 \\rightarrow \\pi^+\\pi^-$ is significantly suppressed. CP - violating $\\pi^+\\pi^-$ decays of pseudoscalar $\\eta_c$ and $\\eta(547)$ mesons in the magnetic field are discussed, and superpositions of quarkonium states $\\eta_{c,b}$ and $\\chi_{c,b}(nP)$ with $\\Psi(nS), \\Upsilon(nS)$ mesons in the external field are considered.
Challenges of Measuring Coronal Magnetic Fields
P. Judge
2002-01-01
Measurements of components of the vector magnetic field in the solar corona can potentially yield information critical to our understanding of coronal structure, dynamics and heating. I will review techniques for making such measurements, in particular those that can be applied outside of active regions. Forbidden coronal emission lines appear to have the highest potential to address outstanding problems in
Killing Vector Fields of Standard Static Space-times
Fernando Dobarro; Bulent Unal
2008-01-30
We consider Killing vector fields on standard static space-times and obtain equations for a vector field on a standard static space-time to be Killing. We also provide a characterization of Killing vector fields on standard static space-times with compact Riemannian parts.
The Helmholtz decomposition of decreasing and weakly increasing vector fields
Petrascheck, D
2015-01-01
Helmholtz decomposition theorem for vector fields is presented usually with too strong restrictions on the fields. Based on the work of Blumenthal of 1905 it is shown that the decomposition of vector fields is not only possible for asymptotically weakly decreasing vector fields, but even for vector fields, which asymptotically increase sublinearly. Use is made of a regularizatin of the Greens function and the mathematics of the proof is formulated as simply as possible. We also show a few examples for the decomposition of vector fields including the electric dipole radiation.
K. F. Rasmussen; J. H. Davies; T. J. E. Miller; M. I. McGelp; M. Olaru
2000-01-01
This paper extends the theory of the air-gap magnetic field in permanent-magnet (PM) brushless motors. Scalar and vector potential solutions to the field equations are brought together to unify many of the important practical methods already in use. The theory admits a more general representation of the magnetization vector than has been previously assumed, including both the radial and tangential
Theory of cosmological seed magnetic fields
Saleem, H. [Theoretical Plasma Physics Division (TPPD), PINSTECH, P. O. Nilore, Islamabad (Pakistan)
2007-07-15
A theory for the generation of seed magnetic field and plasma flow on cosmological scales driven by externally given baroclinic vectors is presented. The Beltrami-like plasma fields can grow from zero values at initial time t=0 from a nonequilibrium state. Exact analytical solutions of the set of two-fluid equations are obtained that are valid for large plasma {beta}-values as well. Weaknesses of previous models for seed magnetic field generation are also pointed out. The analytical calculations predict the galactic seed magnetic field generated by this mechanism to be of the order of 10{sup -14} G, which may be amplified later by the {alpha}{omega} dynamo (or by some other mechanism) to the present observed values of the order of {approx}(2-10) {mu}G. The theory has been applied to laser-induced plasmas as well and the estimate of the magnetic field's magnitude is in agreement with the experimentally observed values.
NASA Astrophysics Data System (ADS)
Beck, Rainer
The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic 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; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent 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. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field ? -? dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos around edge-on galaxies out to large distances from the plane, with X-shaped patterns. In the outflow cone above a starburst region of NGC 253, RM data indicate a helical magnetic field.
An educational path for the magnetic vector potential and its physical implications
NASA Astrophysics Data System (ADS)
Barbieri, S.; Cavinato, M.; Giliberti, M.
2013-09-01
We present an educational path for the magnetic vector potential A aimed at undergraduate students and pre-service physics teachers. Starting from the generalized Ampère-Laplace law, in the framework of a slowly varying time-dependent field approximation, the magnetic vector potential is written in terms of its empirical references, i.e. the conduction currents. Therefore, once the currents are known, our approach allows for a clear and univocal physical determination of A, overcoming the mathematical indeterminacy due to the gauge transformations. We have no need to fix a gauge, since for slowly varying time-dependent electric and magnetic fields, the ‘natural’ gauge for A is the Coulomb one. We stress the difference between our approach and those usually presented in the literature. Finally, a physical interpretation of the magnetic vector potential is discussed and some examples of the calculation of A are analysed.
He I VECTOR MAGNETOMETRY OF FIELD-ALIGNED SUPERPENUMBRAL FIBRILS
Schad, T. A. [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); Penn, M. J. [National Solar Observatory, Tucson, AZ 85719 (United States); Lin, H. [Institute for Astronomy, University of Hawaii, Pukalani, HI 96768 (United States)
2013-05-10
Atomic-level polarization and Zeeman effect diagnostics in the neutral helium triplet at 10830 A in principle allow full vector magnetometry of fine-scaled chromospheric fibrils. We present high-resolution spectropolarimetric observations of superpenumbral fibrils in the He I triplet with sufficient polarimetric sensitivity to infer their full magnetic field geometry. He I observations from the Facility Infrared Spectropolarimeter are paired with high-resolution observations of the H{alpha} 6563 A and Ca II 8542 A spectral lines from the Interferometric Bidimensional Spectrometer from the Dunn Solar Telescope in New Mexico. Linear and circular polarization signatures in the He I triplet are measured and described, as well as analyzed with the advanced inversion capability of the ''Hanle and Zeeman Light'' modeling code. Our analysis provides direct evidence for the often assumed field alignment of fibril structures. The projected angle of the fibrils and the inferred magnetic field geometry align within an error of {+-}10 Degree-Sign . We describe changes in the inclination angle of these features that reflect their connectivity with the photospheric magnetic field. Evidence for an accelerated flow ({approx}40 m s{sup -2}) along an individual fibril anchored at its endpoints in the strong sunspot and weaker plage in part supports the magnetic siphon flow mechanism's role in the inverse Evershed effect. However, the connectivity of the outer endpoint of many of the fibrils cannot be established.
Magnetic Field Measurements in Beam Guiding Magnets
K. N. Henrichsen
1998-01-01
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
High field superconducting magnets
NASA Technical Reports Server (NTRS)
Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)
2011-01-01
A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.
Numerical dosimetry of currents induced in the human body by ELF magnetic fields
Paris-Sud XI, Université de
Numerical dosimetry of currents induced in the human body by ELF magnetic fields Riccardo Scorretti by ELF magnetic fields requires that the source field is provided through a vector potential. We present experimental measurements, as there is no need for a magnetic vector potential. Keywords: ELF, numerical
The history of polarisation measurements: their role in studies of magnetic fields
NASA Astrophysics Data System (ADS)
Wielebinski, R.
2015-03-01
Radio astronomy gave us new methods to study magnetic fields. Synchrotron radiation, the main cause of comic radio waves, is highly linearly polarised with the `E' vector normal to the magnetic field. The Faraday Effect rotates the `E' vector in thermal regions by the magnetic field in the line of sight. Also the radio Zeeman Effect has been observed.
Magnetic Gradiometer and Vector Magnetometer Survey of the Galapagos Triple Junction
NASA Astrophysics Data System (ADS)
Gee, J.; Cande, S. C.; Parker, R. L.; Lonsdale, P. F.; Bowles, J.
2004-05-01
Several fundamental tectonic problems of the equatorial Pacific remain unsolved due to the lack of magnetic anomaly data. A basic limitation encountered with the use of the standard proton precession magnetometer (or any total field instrument) is that total field anomalies over approximately N/S striking bodies are very small at low magnetic latitudes. Another problem encountered with magnetic surveys near the magnetic equator are the diurnal variations associated with the external field. Measurements of the vector anomalous field and total field gradient offer ways to overcome these limitations. Total field gradiometer data allow recognition and removal of time dependent external field variations. Vector magnetic anomalies provide two distinct advantages over total field measurements. Although the total field anomalies are small (typically 50 nT) over most of the equatorial Pacific, the vertical and horizontal components of the anomalous field are 2-5 times larger. In addition, vector anomaly data can be used to evaluate the two dimensionality of the magnetic source since the along track and vertical anomalies are related by a 90o phase shift for a perfectly two dimensional source. To evaluate the advantages of these systems, we conducted a survey of the trails of the Galapagos triple junction using both a high resolution total field gradiometer and a vector magnetometer. The longitudinal gradiometer system consists of two Overhauser sensors (0.01 nT sensitivity) towed 350 and 450m behind the survey vessel. The towed vector magnetometer utilizes a commercial motion reference sensor (0.02o orientation accuracy with three fluxgate sensors) suitable for measuring horizontal and vertical anomalies as small as 30-50 nT. Vector anomalies across Cocos-Nazca crust corroborate the high degree of linearity of these E/W lineations; horizontal and vertical anomalies exhibit high coherence (>0.9) and the expected 90o phase relationship at wavelengths longer than ~8km. Vector data from lower amplitude Pacific-Cocos and Pacific-Nazca lineations are more difficult to interpret, with lower coherence at somewhat longer wavelengths (>11km). The lower apparent degree of linearity over these N/S lineations in part reflects the much higher amplitude of any three dimensional sources. The combined use of vector and gradiometer measurements shows considerable promise for mapping magnetic lineations in low latitude regions.
Slow decay of magnetic fields in open Friedmann universes
Barrow, John D. [DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Tsagas, Christos G. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, Thessaloniki 54124 (Greece)
2008-05-15
Magnetic fields in Friedmann universes can experience superadiabatic growth without departing from conventional electromagnetism. The reason is the relativistic coupling between vector fields and spacetime geometry, which slows down the decay of large-scale magnetic fields in open universes, compared to that seen in perfectly flat models. The result is a large relative gain in magnetic strength that can lead to astrophysically interesting B fields, even if our Universe is only marginally open today.
NSDL National Science Digital Library
Roberta Johnson
2000-07-01
This section of the Windows to the Universe website provides information and images about Earth's magnetic field (the magnetosphere), including detailed information about the aurora borealis, magnets, and solar wind. Windows to the Universe is a user-friendly learning system pertaining to the Earth and Space sciences. The objective of this project is to develop an innovative and engaging website that includes a rich array of documents, including images, movies, animations, and data sets that explore the Earth and Space sciences and the historical and cultural ties between science, exploration and the human experience. Links at the top of each page allow users to navigate between beginner, intermediate and advanced levels.
Full vector low-temperature magnetic measurements of geologic materials
NASA Astrophysics Data System (ADS)
Feinberg, Joshua M.; Solheid, Peter A.; Swanson-Hysell, Nicholas L.; Jackson, Mike J.; Bowles, Julie A.
2015-01-01
magnetic properties of geologic materials offer insights into an enormous range of important geophysical phenomena ranging from inner core dynamics to paleoclimate. Often it is the low-temperature behavior (<300 K) of magnetic minerals that provides the most useful and highest sensitivity information for a given problem. Conventional measurements of low-temperature remanence are typically conducted on instruments that are limited to measuring one single-axis component of the magnetization vector and are optimized for measurements in strong fields. These instrumental limitations have prevented fully optimized applications and have motivated the development of a low-temperature probe that can be used for low-temperature remanence measurements between 17 and 300 K along three orthogonal axes using a standard 2G Enterprises SQuID rock magnetometer. In this contribution, we describe the design and implementation of this instrument and present data from five case studies that demonstrate the probe's considerable potential for future research: a polycrystalline hematite sample, a polycrystalline hematite and magnetite mixture, a single crystal of magnetite, a single crystal of pyrrhotite, and samples of Umkondo Large Igneous Province diabase sills.
Magnetic Field Activities for the High School Classroom
NSDL National Science Digital Library
Ed Eckel
This unit is designed to acquaint students with the properties of magnetic fields. It is meant to introduce the idea of a "field" through investigations of magnetic fields as produced by various common magnetic materials and direct electrical currents. They will learn that the difference between a magnetic field and a gravitational field is that a gravitational field, in the experience of a student, always points downward and is always of the same strength. Magnetic fields are not limited to one direction or strength. Further, all students will know, by the mid-point of this unit, that magnetic fields are inherently loop shaped. Familiarity with the uniform gravitational field of classical Newtonian dynamics and kinematics is not required. As they complete the unit, students will gain an appreciation for the vector nature of fields, the ubiquity of field sources in the environment, and the ability to visualize such fields as three-dimensional entities.
Low field magnetic resonance imaging
Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)
2010-07-13
A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.
Simulation of lightning magnetic field
Chen Yazhou; Wu Xiaorong; Liu Shanghe; Zhang Feizhou
2002-01-01
The lightning magnetic field is simulated when a pulse current is injected into the loop from the lightning surge generator. Different waveforms of lightning magnetic field can be simulated by regulating the parameters of the loop according to the relation between the parameters of the loop and the simulated wave. The dot loop is made to measure the magnetic field
The WIND magnetic field investigation
R. P. Lepping; M. H. Ac?na; L. F. Burlaga; W. M. Farrell; J. A. Slavin; K. H. Schatten; F. Mariani; N. F. Ness; F. M. Neubauer; Y. C. Whang; J. B. Byrnes; R. S. Kennon; P. V. Panetta; J. Scheifele; E. M. Worley
1995-01-01
The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and
AC Magnetic Field Survey Report
Krstic, Miroslav
AC Magnetic Field Survey Report of Literature Building - 3000 University of California San Diego:..........................................................................................................2 ELF OR AC MAGNETIC FIELD CHARACTERISTICS:...............................................2 UNITS of California San Diego La Jolla, California PROJECT: AC Magnetic Field Survey SCOPE: The scope of this project
Stray Field Magnetic Resonance Imaging
K. Zick
1994-01-01
In many applications of magnetic resonance imaging large linewidths means that to achieve useful resolution in the image large magnetic field gradients should be employed. This paper outlines the principles of stray field imaging that utilises the large gradients intrinsic to the fringe field of superconducting solenoidal magnets. Examples of images from strongly broadened everyday objects are given.
Casimir effect of massive vector fields
NASA Astrophysics Data System (ADS)
Teo, L. P.
2010-11-01
We study the Casimir effect due to a massive vector field in a system of two parallel plates made of real materials, in an arbitrary magnetodielectric background. The plane waves satisfying the Proca equations are classified into transverse modes and longitudinal modes which have different dispersion relations. Transverse modes are further divided into type I and type II corresponding to TE and TM modes in the massless case. For general magnetodielectric media, we argue that the correct boundary conditions are the continuities of H?, ?, A, and ?xAx, where x is the direction normal to the plates. Although there are type I transverse modes that satisfy all the boundary conditions, it is impossible to find type II transverse modes or longitudinal modes that satisfy all the boundary conditions. To circumvent this problem, type II transverse modes and longitudinal modes have to be considered together. We call the contribution to the Casimir energy from type I transverse modes TE contribution, and the contribution from the superposition of type II transverse modes and longitudinal modes TM contribution. Their massless limits give, respectively, the TE and TM contributions to the Casimir energy of a massless vector field. The limit where the plates become perfectly conducting is discussed in detail. For the special case where the background has a unity refractive index, it is shown that the TM contribution to the Casimir energy can be written as a sum of contributions from two different types of modes, corresponding to type II discrete modes and type III continuum modes discussed by Barton and Dombey [G. Barton and N. Dombey, Ann. Phys. (N.Y.)APNYA60003-4916 162, 231 (1985).10.1016/0003-4916(85)90162-9]. For general background, this splitting does not work. The limit where both plates become infinitely permeable and the limit where one plate becomes perfectly conducting and one plate becomes infinitely permeable are also investigated.
Robust point matching via vector field consensus.
Jiayi Ma; Ji Zhao; Jinwen Tian; Yuille, Alan L; Zhuowen Tu
2014-04-01
In this paper, we propose an efficient algorithm, called vector field consensus, for establishing robust point correspondences between two sets of points. Our algorithm starts by creating a set of putative correspondences which can contain a very large number of false correspondences, or outliers, in addition to a limited number of true correspondences (inliers). Next, we solve for correspondence by interpolating a vector field between the two point sets, which involves estimating a consensus of inlier points whose matching follows a nonparametric geometrical constraint. We formulate this a maximum a posteriori (MAP) estimation of a Bayesian model with hidden/latent variables indicating whether matches in the putative set are outliers or inliers. We impose nonparametric geometrical constraints on the correspondence, as a prior distribution, using Tikhonov regularizers in a reproducing kernel Hilbert space. MAP estimation is performed by the EM algorithm which by also estimating the variance of the prior model (initialized to a large value) is able to obtain good estimates very quickly (e.g., avoiding many of the local minima inherent in this formulation). We illustrate this method on data sets in 2D and 3D and demonstrate that it is robust to a very large number of outliers (even up to 90%). We also show that in the special case where there is an underlying parametric geometrical model (e.g., the epipolar line constraint) that we obtain better results than standard alternatives like RANSAC if a large number of outliers are present. This suggests a two-stage strategy, where we use our nonparametric model to reduce the size of the putative set and then apply a parametric variant of our approach to estimate the geometric parameters. Our algorithm is computationally efficient and we provide code for others to use it. In addition, our approach is general and can be applied to other problems, such as learning with a badly corrupted training data set. PMID:24808341
Smooth Normal Linearization of Vector Fields Near Lines of Singularities
Freddy Dumortier; Robert Roussarie
2010-01-01
The paper deals with smooth three-dimensional vector fields exhibiting a line of singularities. For a large class of such\\u000a vector fields we prove a theorem of smooth $${({\\\\mathcal{C}}^\\\\infty)}$$ normal linearization along the line of singularities, near well chosen points. The vector fields can depend on a multiparameter\\u000a and if they are subject to certain symmetries then the same symmetries can
Digital vector magnetograph. I. Longitudinal field channel.
NASA Astrophysics Data System (ADS)
Gopasyuk, S. I.; Zalesov, I. P.
1996-01-01
A digital magnetograph for measuring longitudinal magnetic fields is described. The principle of digital synchronous detection is applied in the magnetograph system. Results of test observations made in 1995 are presented. The maximum noise amplitude was found to be less than 1.5 mT with an integration time of 0.05 s and an aperture of 1×4 arcsec. Observations of a region of 200×200 arcsec on the solar surface require about 10 min with an aperture of 1×4 arcsec.
NASA Astrophysics Data System (ADS)
Kong, Seong Deok
Hollow-sphere nanocapsules containing intentionally trapped magnetic nanoparticles and defined anticancer drugs provide a powerful magnetic vector under moderate gradient magnetic fields, and enable the nanocapsules to penetrate into the midst of tumors and allow a controlled on-off switchable release of the anticancer drug cargo by remotely applied Radio Frequency (RF) magnetic field. This imageable smart drug delivery system is compact because the drug molecules and magnetic nanoparticles can all be self-contained within 80~150 nm capsules. In vitro as well as in vivo results indicate that the nanocapsules are effective in reducing tumor cell growth. In Chapter 1, the concept of Drug Delivery Systems (DDSs) and the impact of nanotechnology on Drug Delivery Systems were introduced. Triggered drug release using magnetothermally-responsive nanomaterials, magnetic nanoparticles for nanomedicine, and ordered mesoporous materials in the context of Drug Delivery System were discussed. In Chapter 2, creation of remotely controllable, On-Off switchable drug release methodology was described. In this thesis work, triggerable nanocapsules which contain magnetic nanoparticles responsive to external radio frequency (RF) magnetic field have been successfully created. This is in contrast to the regular hollow nanospheres for slow passive release of drugs. The new nanocapsule material consists of bio-inert, bio-compatible or bio-degradable material that we can be selected from a variety of materials depending on specific medical applications. In Chapter 3, study and utilization of magnetic vector for guided tumor penetration was discussed. In the presence of a moderate gradient magnetic field, a powerful magnetic vector is created that allows these nanocapsules to cross cell membranes or blood-tissue barriers and penetrate into the midst of tumors, thus overcoming the well-known problem of limited access of anti-cancer drugs to cancer cells in the interior of a tumor tissue. In Chapter 4, potential applications to Blood-Brain-Barrier (BBB) crossing and other therapeutics was described. In Chapter 5, the study was summarized and concluded.
GRIMM: the GFZ Reference Internal Magnetic Model based on vector satellite and observatory data
Vincent Lesur; Ingo Wardinski; Martin Rother; Mioara Mandea
2008-01-01
In this paper the new GFZ Reference Internal Magnetic Model (GRIMM) is presented. The model has been derived from nearly 6 yr of CHAMP satellite data and 5 yr of observatory hourly means. At high latitudes, full vector satellite data are used at all local times which allows a separation between, on one hand, the fields generated by ionosphere and
Tracking Vector Magnetograms with the Magnetic Induction Equation
NASA Technical Reports Server (NTRS)
Schuck, P.
2009-01-01
The differential affine velocity estimator (DAVE) that we developed in 2006 for estimating velocities from line-of-sight magnetograms is modified to directly incorporate horizontal magnetic fields to produce a differential affine velocity estimator for vector magnetograms (DAVE4VM). The DAVE4VM's performance is demonstrated on the synthetic data from the anelastic pseudospectral ANMHD simulations that were used in the recent comparison of velocity inversion techniques by Welsch and coworkers. The DAVE4VM predicts roughly 95% of the helicity rate and 75% of the power transmitted through the simulation slice. Intercomparison between DAVE4VM and DAVE and further analysis of the DAVE method demonstrates that line-of-sight tracking methods capture the shearing motion of magnetic footpoints but are insensitive to flux emergence - the velocities determined from line-of-sight methods are more consistent with horizontal plasma velocities than with flux transport velocities. These results suggest that previous studies that rely on velocities determined from line-of-sight methods such as the DAVE or local correlation tracking may substantially misrepresent the total helicity rates and power through the photosphere.
On the Computation of Integral Curves in Adaptive Mesh Refinement Vector Fields
Deines, Eduard; Weber, Gunther H.; Garth, Christoph; Van Straalen, Brian; Borovikov, Sergey; Martin, Daniel F.; Joy, Kenneth I.
2011-06-27
Integral curves, such as streamlines, streaklines, pathlines, and timelines, are an essential tool in the analysis of vector field structures, offering straightforward and intuitive interpretation of visualization results. While such curves have a long-standing tradition in vector field visualization, their application to Adaptive Mesh Refinement (AMR) simulation results poses unique problems. AMR is a highly effective discretization method for a variety of physical simulation problems and has recently been applied to the study of vector fields in flow and magnetohydrodynamic applications. The cell-centered nature of AMR data and discontinuities in the vector field representation arising from AMR level boundaries complicate the application of numerical integration methods to compute integral curves. In this paper, we propose a novel approach to alleviate these problems and show its application to streamline visualization in an AMR model of the magnetic field of the solar system as well as to a simulation of two incompressible viscous vortex rings merging.
Magnetic-field dependence of coupled Luttinger chains
Schmeltzer, D. [Department of Physics, City College of the City University of New York, New York, New York 10031 (United States)] [Department of Physics, City College of the City University of New York, New York, New York 10031 (United States); Bishop, A.R. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
1998-03-01
The model of two coupled Luttinger chains in the presence of a magnetic field is investigated for weak and strong magnetic field strengths. For magnetic fields that are close to the commensurate wave vector condition Q{approx}2 K{sub F} (with K{sub F} the Fermi wave vector), incoherent tunneling between the chains takes place. Under these conditions, we propose that the incoherent non-Fermi-liquid Anderson fixed point is realized. Implications for the normal-state behavior of organic and cuprate superconductors are discussed. {copyright} {ital 1998} {ital The American Physical Society}
Coronal magnetic fields from microwave polarization observations
C. E. Alissandrakis; F. Borgioli; F. Chiuderi Drago; M. Hagyard; K. Shibasaki
1996-01-01
The solar active region (AR) 7530 was observed at 6 cm on July 3 and 4, 1993 with the Westerbork Synthesis Radio Telescope, using a multi-channel receiver with very narrow bandwidth. We compare the radio data with Yohkoh SXT observations and with the magnetic field extrapolated from the Marshall vector magnetograms in the force-free and current-free approximations. The comparison with
(version 6/26/06) Magnetic Fields
Collins, Gary S.
(version 6/26/06) Magnetic Fields GOALS (1) To visualize the magnetic fields produced by several to trace out the magnetic field lines of a single bar magnet on a large sheet of paper. (3) To calculate where the magnetic fields of the Earth and the bar magnet sum to zero. INTRODUCTION A magnetic field
Phillips, J.D.; Nabighian, M.N.; Smith, D.V.; Li, Y.
2007-01-01
The Helbig method for estimating total magnetization directions of compact sources from magnetic vector components is extended so that tensor magnetic gradient components can be used instead. Depths of the compact sources can be estimated using the Euler equation, and their dipole moment magnitudes can be estimated using a least squares fit to the vector component or tensor gradient component data. ?? 2007 Society of Exploration Geophysicists.
Confined Dirac particles in a constant and tilted magnetic field
NASA Astrophysics Data System (ADS)
Alhaidari, Abdulaziz D.; Bahlouli, Hocine; Jellal, Ahmed
2015-04-01
We study the confinement of charged Dirac particles in a plane embedded in 3 + 1 space-time due to the presence of a constant magnetic field that is tilted on the given plane. We focus on the nature of the solutions of the Dirac equation and on how they depend on the choice of vector potential that gives rise to the magnetic field. In particular, we select a "Landau gauge" such that the momentum is conserved along the direction of the vector potential yielding spinor wave functions, which are localized in the plane containing the magnetic field and normal to the vector potential. These wave functions are expressed in terms of the Hermite polynomials. We point out the relevance of these findings to the relativistic quantum Hall effect and compare with the results obtained for a constant magnetic field normal to the plane in 2 + 1 dimensions.
Video-rate terahertz electric-field vector imaging
NASA Astrophysics Data System (ADS)
Takai, Mayuko; Takeda, Masatoshi; Sasaki, Manabu; Tachizaki, Takehiro; Yasumatsu, Naoya; Watanabe, Shinichi
2014-10-01
We present an experimental setup to dramatically reduce a measurement time for obtaining spatial distributions of terahertz electric-field (E-field) vectors. The method utilizes the electro-optic sampling, and we use a charge-coupled device to detect a spatial distribution of the probe beam polarization rotation by the E-field-induced Pockels effect in a ?110?-oriented ZnTe crystal. A quick rotation of the ZnTe crystal allows analyzing the terahertz E-field direction at each image position, and the terahertz E-field vector mapping at a fixed position of an optical delay line is achieved within 21 ms. Video-rate mapping of terahertz E-field vectors is likely to be useful for achieving real-time sensing of terahertz vector beams, vector vortices, and surface topography. The method is also useful for a fast polarization analysis of terahertz beams.
The external magnetic field environment
NASA Technical Reports Server (NTRS)
1977-01-01
Calculations were made to predict magnetic field intensities surrounding an aircraft following a lightning strike. Aircraft design and aircraft structural geometry were considered in the computations. A wire grid aircraft model was used to aid in magnetic flux estimation.
Magnetic fields of degenerate stars
NASA Astrophysics Data System (ADS)
Chanmugam, G.
The magnetic fields of degenerate stars are discussed with emphasis on such basic issues as how their magnetic field strengths are determined, their origin, and evolution. The magnetic fields of both white dwarfs and neutron stars are discussed together, and it is speculated that the origin and evolution of their fields may be related. It is also suggested that it may be possible to apply and test models for the evolution of the magnetic fields in neutron stars by using white dwarfs and vice versa.
Fast superconducting magnetic field switch
Goren, Y.; Mahale, N.K.
1996-08-06
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.
Fast superconducting magnetic field switch
Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)
1996-01-01
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.
Martian external magnetic field proxies
NASA Astrophysics Data System (ADS)
Langlais, Benoit; Civet, Francois
2015-04-01
Mars possesses no dynamic magnetic field of internal origin as it is the case for the Earth or for Mercury. Instead Mars is characterized by an intense and localized magnetic field of crustal origin. This field is the result of past magnetization and demagnetization processes, and reflects its evolution. The Interplanetary Magnetic Field (IMF) interacts with Mars' ionized environment to create an external magnetic field. This external field is weak compared to lithospheric one but very dynamic, and may hamper the detailed analysis of the internal magnetic field at some places or times. Because there are currently no magnetic field measurements made at Mars' surface, it is not possible to directly monitor the external field temporal variability as it is done in Earth's ground magnetic observatories. In this study we examine to indirect ways of quantifying this external field. First we use the Advanced Composition Explorer (ACE) mission which measures the solar wind about one hour upstream of the bow-shock resulting from the interaction between the solar wind and the Earth's internal magnetic field. These measurements are extrapolated to Mars' position taking into account the orbital configurations of the Mars-Earth system and the velocity of particles carrying the IMF. Second we directly use Mars Global Surveyor magnetic field measurements to quantify the level of variability of the external field. We subtract from the measurements the internal field which is otherwise modeled, and bin the residuals first on a spatial and then on a temporal mesh. This allows to compute daily or semi daily index. We present a comparison of these two proxies and demonstrate their complementarity. We also illustrate our analysis by comparing our Martian external field proxies to terrestrial index at epochs of known strong activity. These proxies will especially be useful for upcoming magnetic field measurements made around or at the surface of Mars.
The Curl of a Vector Field: Beyond the Formula
ERIC Educational Resources Information Center
Burch, Kimberly Jordan; Choi, Youngna
2006-01-01
It has been widely acknowledged that there is some discrepancy in the teaching of vector calculus in mathematics courses and other applied fields. The curl of a vector field is one topic many students can calculate without understanding its significance. In this paper, we explain the origin of the curl after presenting the standard mathematical…
Robust Morse Decompositions of Piecewise Constant Vector Fields
Szymczak, Andrzej
to color code the Morse sets in order to enhance the visualization. We demonstrate the benefits of our1 Robust Morse Decompositions of Piecewise Constant Vector Fields Andrzej Szymczak, Member, IEEE to computing a Morse decomposition of a vector field on a triangulated manifold surface. The basic idea
Primordial magnetic fields from self-ordering scalar fields
Horiguchi, Kouichirou; Sekiguchi, Toyokazu; Sugiyama, Naoshi
2015-01-01
A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by $B\\sim{10^{-9}}{((1+z)/10^3)^{-2.5}}({v}/{m_{\\rm pl}})^2({k}/{\\rm Mpc^{-1}})^{3.5}/{\\sqrt{N}}$ Gauss in the radiation dominated era for $k\\lesssim 1$ Mpc$^{-1}$, with $v$ being the vacuum ...
Evolution of twisted magnetic fields
Zweibel, E.G.; Boozer, A.H.
1985-02-01
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.
Design of 2D time-varying vector fields.
Chen, Guoning; Kwatra, Vivek; Wei, Li-Yi; Hansen, Charles D; Zhang, Eugene
2012-10-01
Design of time-varying vector fields, i.e., vector fields that can change over time, has a wide variety of important applications in computer graphics. Existing vector field design techniques do not address time-varying vector fields. In this paper, we present a framework for the design of time-varying vector fields, both for planar domains as well as manifold surfaces. Our system supports the creation and modification of various time-varying vector fields with desired spatial and temporal characteristics through several design metaphors, including streamlines, pathlines, singularity paths, and bifurcations. These design metaphors are integrated into an element-based design to generate the time-varying vector fields via a sequence of basis field summations or spatial constrained optimizations at the sampled times. The key-frame design and field deformation are also introduced to support other user design scenarios. Accordingly, a spatial-temporal constrained optimization and the time-varying transformation are employed to generate the desired fields for these two design scenarios, respectively. We apply the time-varying vector fields generated using our design system to a number of important computer graphics applications that require controllable dynamic effects, such as evolving surface appearance, dynamic scene design, steerable crowd movement, and painterly animation. Many of these are difficult or impossible to achieve via prior simulation-based methods. In these applications, the time-varying vector fields have been applied as either orientation fields or advection fields to control the instantaneous appearance or evolving trajectories of the dynamic effects. PMID:22201068
Helicity of the Solar Magnetic Field
NASA Astrophysics Data System (ADS)
Tiwari, Sanjiv Kumar
2009-11-01
Magnetic helicity is a physical quantity that measures the degree of linkages and twistedness in the field lines. It is given by a volume integral over the scalar product of magnetic field B and its vector potential A. Direct computation of magnetic helicity in the solar atmosphere is not possible due to two reasons. First, we do not have the observations at different heights in the solar atmosphere to compute the volume integral. Second, the vector potential A is non-unique owing to gauge variance. Many researchers incorrectly inferred twist, a component of magnetic helicity, from the force-free parameter Î±. We clarified the physical meaning of Î± and its relation with the magnetic helicity. Also, a direct method is proposed for the computation of global Î± values of sunspots. An analytical bipole was generated to study the effect of polarimetric noise on the estimation of various magnetic parameters. We find that the effect of polarimetric noise, present in the recent vector magnetograms e.g., from Hinode (Solar Optical Telescope/Spectro- Polarimeter (SOT/SP)), on the magnetic parameters like Î± and magnetic energy, is negligible. We examined the fine structures of local current and Î± in the sunspots. Local Î± patches of opposite signs are present in the umbra of each sunspot. The amplitude of the spatial variation of local Î± in the umbra is typically of the order of the global Î± of the sunspot. We find that the local Î± and current are distributed as alternately positive and negative filaments in the penumbra. The amplitude of azimuthal variation of the local Î± in the penumbra is approximately an order of magnitude larger than that in the umbra. The contributions of the local positive and negative currents and Î± in the penumbra cancel each other giving almost no contribution for their global values for whole sunspot. We have introduced the concept of signed shear angle (SSA) for sunspots and establish its importance for non force-free fields. The spatially averaged SSA (SASSA) gives the actual twist present in ! a sunspot irrespective of the force-free nature and the shape of the sunspot. We find that the sign of global Î± is well correlated with the SASSA of the sunspots but the magnitudes are not. We find that there is no net current in the sunspots, although there is significant twist present in the photospheric magnetic field of the sunspots. The existence of a global twist for a sunspot even in the absence of a net current is consistent with the fibril-bundle structure of the sunspot magnetic fields. We also discovered the curly interlocking combed structure in the azimuthal component of sunspot magnetic field. We studied the SASSA of sunspots to predict the flare activity of the associated active regions. We studied the evolution of vector magnetic fields using a large number of vector magnetograms of both, an eruptive and a non-eruptive sunspot. We arrive at a critical threshold value of the SASSA for each class of X-ray flare associated with these two sunspots. Thus, the SASSA holds promise to be very useful in predicting the probability of the occurrence of solar flares. A good correlation is found between the sign of helicity in the sunspots at the photosphere and the chirality of the associated chromospheric and coronal features. This study will be very useful as a constraint while modeling the Chromospheric and coronal features. We find that a large number of sunspots observed in the declining phase of the solar cycle 23 follow the reverse hemispheric helicity rule. Most of the sunspots observed in the beginning of new solar cycle 24 follow the conventional hemispheric helicity rule. This indicates a long term behaviour of the helicity patterns in the solar atmosphere. However, this needs to be confirmed with the data sets spanning large number of years.
Cyclical magnetic field flow fractionation
NASA Astrophysics Data System (ADS)
Tasci, T. O.; Johnson, W. P.; Gale, B. K.
2012-04-01
In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 ?m) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.
A 50-degree spherical harmonic model of the magnetic field of Mars
Jafar Arkani-Hamed
2001-01-01
This paper presents a 50-degree and order spherical harmonic model of the magnetic field of Mars derived at 120-km altitude using the three orthogonal components of the vector magnetic field data acquired by the Mars Global Surveyor within the 80-to 200-km-altitude range. The downward continued vector magnetic field components to the surface of Mars delineate details of the Martian magnetic
Ionospheric magnetic fields at Venus and Mars
NASA Astrophysics Data System (ADS)
Dubinin, E.; Fraenz, M.; Zhang, T. L.; Woch, J.; Wei, Y.
2014-04-01
Mars Global Surveyor (MGS) and Venus Express(VEX) spacecraft have provided us a wealth of insitu observations of characteristics of induced magnetospheres of Mars and Venus at low altitudes during the periods of solar minimum. At such conditions the interplanetary magnetic field (IMF) penetrates deeply inside the ionosphere while the solar wind is terminated at higher altitudes. We present the measurements made by MGS and VEX in the ionospheres of both planets which reveal similar features of the magnetization. The arising magnetic field pattern occurs strongly asymmetrical with respect to the direction of the cross-flow component of the IMF revealing either a sudden straightening of the field lines with a release of the magnetic field stresses or a sudden rotation of the magnetic field vector with a reversal of the sign of the cross-flow component. Such an asymmetrical response is observed at altitudes where the motion of ions and electrons is decoupled and collisional effects become important for generation of the electric currents Asymmetry in the field topology significantly modifies a plasma transport to the night side.
Magnetic field fluctuations in SC dipole magnet
Vladimir Shiltsev et al.
2001-08-15
Magnetic field fluctuations at the betatron frequency can lead to emittance growth in circular accelerators. Tolerances are extremely tight for large hadron colliders like LHC and VLHC[1]. We performed experimental studies of the fluctuations in a stand-alone superconducting Tevatron magnet. Here we give a general description of the experimental set-up, present main results and discuss consequences for the colliders.
Exposure guidelines for magnetic fields
Miller, G.
1987-12-01
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.
Lorentz-violating vector fields slow the universe down
Carroll, Sean M. [Department of Physics, University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States); Enrico Fermi Institute, and Kavli Institute for Cosmological Physics, University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States); Lim, Eugene A. [Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States); Enrico Fermi Institute, and Kavli Institute for Cosmological Physics, University of Chicago, 5640 S. Ellis Avenue, Chicago, Illinois 60637 (United States)
2004-12-15
We consider the gravitational effects of a single, fixed-norm, Lorentz-violating timelike vector field. In a cosmological background, such a vector field acts to rescale the effective value of Newton's constant. The energy density of this vector field precisely tracks the energy density of the rest of the universe, but with the opposite sign, so that the universe experiences a slower rate of expansion for a given matter content. This vector field similarly rescales Newton's constant in the Newtonian limit, although by a different factor. We put constraints on the parameters of the theory using the predictions of primordial nucleosynthesis, demonstrating that the norm of the vector field should be less than the Planck scale by an order of magnitude or more.
Magnetic-field-dosimetry system
Lemon, D.K.; Skorpik, J.R.; Eick, J.L.
1981-01-21
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.
G. V. Rudenko
This paper is concerned with the Laplace boundary-value problem with the directional derivative, corresponding to the specific nature of measurements of the longitudinal component of the photospheric magnetic field. Boundary conditions are specified by a distribution on the sphere of projection of the magnetic field vector unto a given direction. It is shown that the solution of this problem exists
(Revised December 30, 2013) Magnetic Fields
Collins, Gary S.
(Revised December 30, 2013) Magnetic Fields GOALS (1) To visualize the magnetic fields produced compasses to trace out the magnetic field lines of a single bar magnet on a large sheet of paper. (3 of the points where the magnetic fields of the Earth and the bar magnet sum to zero. INTRODUCTION A magnetic
On sunspot magnetic field diffusion.
NASA Astrophysics Data System (ADS)
Krivodubskij, V. N.
The efficiency of different mechanisms of sunspot magnetic field dissipation depending on the stage of sunspot decay and optical depth is investigated. The highest rate of the magnetic field diffusion has place at the initial stage of sunspot decay, when the turbulence motion in the sunspot umbra takes a two-dimensional structure due to the strong magnetic field (B ? 3000 G). The turbulence degeneracy withdraws at the later stage of the sunspot decay (B ? 2000 G) and the dissipation slows down.
Statistical anisotropy of the curvature perturbation from vector field perturbations
Dimopoulos, Konstantinos; Karciauskas, Mindaugas; Lyth, David H. [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)] [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom); Rodriguez, Yeinzon, E-mail: k.dimopoulos1@lancaster.ac.uk, E-mail: m.karciauskas@lancaster.ac.uk, E-mail: d.lyth@lancaster.ac.uk, E-mail: yeinzon.rodriguez@uan.edu.co [Centro de Investigaciones, Universidad Antonio Narino, Cra 3 Este 47A-15, Bogota D.C. (Colombia)] [Centro de Investigaciones, Universidad Antonio Narino, Cra 3 Este 47A-15, Bogota D.C. (Colombia)
2009-05-15
The {delta}N formula for the primordial curvature perturbation {zeta} is extended to include vector as well as scalar fields. Formulas for the tree-level contributions to the spectrum and bispectrum of {zeta} are given, exhibiting statistical anisotropy. The one-loop contribution to the spectrum of {zeta} is also worked out. We then consider the generation of vector field perturbations from the vacuum, including the longitudinal component that will be present if there is no gauge invariance. Finally, the {delta}N formula is applied to the vector curvaton and vector inflation models with the tensor perturbation also evaluated in the latter case.
NASA Astrophysics Data System (ADS)
Back, Randy; Beckham, J. Regan
2012-10-01
A vertically draining thin ferrofilm under the influence of gravity and a nonuniform magnetic field is considered. It is observed experimentally that the presence of the magnetic field greatly alters the drainage of the film. A mathematical model is developed to describe the behavior. Experiments are conducted for multiple magnetic field configurations. The model is solved for two different sets of boundary conditions and results are compared to experiments. It is shown that the magnetic field structure, the concentration of magnetite in the solution, and the boundary conditions all have noticeable affects on the evolution of the thinning film. Good qualitative agreement between the model and the experiments is observed.
The Sun's global magnetic field.
Mackay, Duncan H
2012-07-13
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
Magnetic fields around evolved stars
NASA Astrophysics Data System (ADS)
Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.
2014-04-01
A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.
Axial magnetic field contacts with nonuniform distributed axial magnetic fields
Zongqian Shi; Shenli Jia; Jun Fu; Zheng Wang
2003-01-01
It is well known that axial magnetic fields (AMFs) can keep vacuum arc in diffuse mode at high current. According to our recent research and other published papers, it has been found that vacuum arc can be maintained in high-current diffuse mode at much higher current if nonuniform AMF is applied, that the axial magnetic field is higher at contact
CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Structure of Magnetic
Callen, James D.
CHAPTER 3. STRUCTURE OF MAGNETIC FIELDS 1 Chapter 3 Structure of Magnetic Fields Many of the most interesting plasmas are permeated by or imbedded in magnetic fields.1 As shown in Fig. 3.1, the magnetic field properties of magnetic fields in plasmas can be discussed without specifying a model for the plasma
Visualizing vector fields using line integral convolution and dye advection
Han-Wei Shent; Christopher R. Johnsont; Kwan-Liu Mat
1996-01-01
We present local and global techniques to visualizethree-dimensional vector field data. Using the Line IntegralConvolution (LIC) method to image the globalvector field, our new algorithm allows the user to introducecolored "dye" into the vector field to highlightlocal flow features. A fast algorithm is proposed thatquickly recomputes the dyed LIC images. In addition,we introduce volume rendering methods that can mapthe LIC
Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki
2014-01-21
A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.
Modeling surface magnetic fields in stars with radiative envelopes
NASA Astrophysics Data System (ADS)
Kochukhov, Oleg
2014-08-01
Stars with radiative envelopes, specifically the upper main sequence chemically peculiar (Ap) stars, were among the first objects outside our solar system for which surface magnetic fields have been detected. Currently magnetic Ap stars remains the only class of stars for which high-resolution measurements of both linear and circular polarization in individual spectral lines are feasible. Consequently, these stars provide unique opportunities to study the physics of polarized radiative transfer in stellar atmospheres, to analyze in detail stellar magnetic field topologies and their relation to starspots, and to test different methodologies of stellar magnetic field mapping. Here I present an overview of different approaches to modeling the surface fields in magnetic A- and B-type stars. In particular, I summarize the ongoing efforts to interpret high-resolution full Stokes vector spectra of these stars using magnetic Doppler imaging. These studies reveal an unexpected complexity of the magnetic field geometries in some Ap stars.
Measurements of magnetic field alignment
Kuchnir, M.; Schmidt, E.E.
1987-11-06
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.
HMI Measurements Of The Solar Magnetic Field
NASA Astrophysics Data System (ADS)
Hoeksema, Jon Todd; HMI Magnetic Field Team
2011-05-01
The Helioseismic and Magnetic Imager (HMI) on NASA's Solar Dynamics Observatory (SDO) routinely produces a comprehensive array of magnetic field data products including 45-second line-of-sight magnetograms, synoptic maps and synchronic frames, 12-minute vector field time series in HMI Active Region Patches (HARPs), model calculations of the coronal field and solar wind, and near-real-time parameters for space weather. Other products, such as surface flow maps, can be produced on demand or on request. We present examples of data products generated during the first year of operations and compare some of these with measurements from other observatories, including the now-dormant MDI. The HMI Team is sponsored by NASA.
Non-Gaussianity from Cosmic Magnetic Fields
Iain Brown; Robert Crittenden
2005-09-22
Magnetic fields in the early universe could have played an important role in sourcing cosmological perturbations. While not the dominant source, even a small contribution might be traceable through its intrinsic non-Gaussianity. Here we calculate analytically the one, two and three point statistics of the magnetic stress energy resulting from tangled Gaussian fields, and confirm these with numerical realizations of the fields. We find significant non-Gaussianity, and importantly predict higher order moments that will appear between the scalar, vector and tensor parts of the stress energy (e.g. scalar-tensor-tensor moments). Such higher order cross correlations are a generic feature of non-linear theories and could prove to be an important probe of the early universe.
Visualizing Vector Fields Using Line Integral Convolution and Dye Advection
NASA Technical Reports Server (NTRS)
Shen, Han-Wei; Johnson, Christopher R.; Ma, Kwan-Liu
1996-01-01
We present local and global techniques to visualize three-dimensional vector field data. Using the Line Integral Convolution (LIC) method to image the global vector field, our new algorithm allows the user to introduce colored 'dye' into the vector field to highlight local flow features. A fast algorithm is proposed that quickly recomputes the dyed LIC images. In addition, we introduce volume rendering methods that can map the LIC texture on any contour surface and/or translucent region defined by additional scalar quantities, and can follow the advection of colored dye throughout the volume.
Energy momentum flows for the massive vector field
George Horton; Chris Dewdney
2006-09-26
We present a causal trajectory interpretation for the massive vector field, based on the flows of rest energy and a conserved density defined using the time-like eigenvectors and eigenvalues of the stress-energy-momentum tensor. This work extends our previous work which used a similar procedure for the scalar field. The massive, spin-one, complex vector field is discussed in detail and solutions are classified using the Pauli-Lubanski spin vector. The flows of energy-momentum are illustrated in a simple example of standing waves in a plane.
Analytical maximum likelihood estimation of stellar magnetic fields
NASA Astrophysics Data System (ADS)
Martínez González, M. J.; Manso Sainz, R.; Asensio Ramos, A.; Belluzzi, L.
2012-01-01
The polarized spectrum of stellar radiation encodes valuable information on the conditions of stellar atmospheres and the magnetic fields that permeate them. In this paper, we give explicit expressions to estimate the magnetic field vector and its associated error from the observed Stokes parameters. We study the solar case where specific intensities are observed and then the stellar case, where we receive the polarized flux. In the second case, we concentrate on the explicit expression for the case of a slow rotator with a dipolar magnetic field geometry. Moreover, we also give explicit formulae to retrieve the magnetic field vector from the least-squares deconvolution (LSD) profiles without assuming mean values for the LSD artificial spectral line. The formulae have been obtained assuming that the spectral lines can be described in the weak-field regime and using a maximum likelihood approach. The errors are recovered by means of the Hermitian matrix. The bias of the estimators is analysed in depth.
Photon Magnetic Moment and Vacuum Magnetization in an Asymptotically Large Magnetic Field
Selym Villalba Chavez
2010-08-09
We consider the effect of the photon radiative correction on the vacuum energy in a superstrong magnetic field. The notion of a photon anomalous magnetic moment is analyzed and its connection with the quasiparticle character of the electromagnetic radiation is established. In the infrared domain the magnetic moment turns out to be a vector with two orthogonal components in correspondence with the cylindrical symmetry imposed by the external field. The possibility of defining such quantity in the high energy limit is studied as well. Its existence suggests that the electromagnetic radiation is a source of magnetization to the whole vacuum and thus its electron-positron zero-point energy is slightly modified. The corresponding contribution to the vacuum magnetization density is determined by considering the individual contribution of each vacuum polarization eigenmode in the Euler-Heisenberg Lagrangian. A paramagnetic response is found in one of them, whereas the remaining ones are diamagnetic. Additional issues concerning the transverse pressures are analyzed.
Photon magnetic moment and vacuum magnetization in an asymptotically large magnetic field
Villalba-Chavez, Selym [Institute of Physics, University of Graz, Universitaetsplatz 5, 8010, Graz (Austria)
2010-05-15
We consider the effect of the photon radiative correction on the vacuum energy in a superstrong magnetic field. The notion of a photon anomalous magnetic moment is analyzed and its connection with the quasiparticle character of the electromagnetic radiation is established. In the infrared domain the magnetic moment turns out to be a vector with two orthogonal components in correspondence with the cylindrical symmetry imposed by the external field. The possibility of defining such quantity in the high energy limit is studied as well. Its existence suggests that the electromagnetic radiation is a source of magnetization to the whole vacuum and thus its electron-positron zero-point energy is slightly modified. The corresponding contribution to the vacuum magnetization density is determined by considering the individual contribution of each vacuum polarization eigenmode in the Euler-Heisenberg Lagrangian. A paramagnetic response is found in one of them, whereas the remaining ones are diamagnetic. Additional issues concerning the transverse pressures are analyzed.
Voigt, J; Knappe-Grüneberg, S; Gutkelch, D; Haueisen, J; Neuber, S; Schnabel, A; Burghoff, M
2015-05-01
Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23 pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method. PMID:26026560
High latitude solar magnetic fields
NASA Technical Reports Server (NTRS)
Murray, Norman
1992-01-01
Kitt Peak magnetograms are used to measure polar magnetic fields. The polar mean absolute field increases at the same time as the polar mean field decreases. That is, the polar mean absolute field varies in phase with solar activity, in contrast to the out of phase variation of the mean polar field. It is found that the polar fields have a large bipolar component even at solar minimum, with a magnitude equal to that found at low latitudes outside the active latitude bands.
Mariappan, Leo; He, Bin
2013-01-01
Magneto acoustic tomography with magnetic induction (MAT-MI) is a technique proposed to reconstruct the conductivity distribution in biological tissue at ultrasound imaging resolution. A magnetic pulse is used to generate eddy currents in the object, which in the presence of a static magnetic field induces Lorentz force based acoustic waves in the medium. This time resolved acoustic waves are collected with ultrasound transducers and, in the present work, these are used to reconstruct the current source which gives rise to the MAT-MI acoustic signal using vector imaging point spread functions. The reconstructed source is then used to estimate the conductivity distribution of the object. Computer simulations and phantom experiments are performed to demonstrate conductivity reconstruction through vector source imaging in a circular scanning geometry with a limited bandwidth finite size piston transducer. The results demonstrate that the MAT-MI approach is capable of conductivity reconstruction in a physical setting. PMID:23322761
Huang, Qiu; Peng, Qiyu; Huang, Bin; Cheryauka, Arvi; Gullberg, Grant T.
2008-05-15
The measurement of flow obtained using continuous wave Doppler ultrasound is formulated as a directional projection of a flow vector field. When a continuous ultrasound wave bounces against a flowing particle, a signal is backscattered. This signal obtains a Doppler frequency shift proportional to the speed of the particle along the ultrasound beam. This occurs for each particle along the beam, giving rise to a Doppler velocity spectrum. The first moment of the spectrum provides the directional projection of the flow along theultrasound beam. Signals reflected from points further away from the detector will have lower amplitude than signals reflected from points closer to the detector. The effect is very much akin to that modeled by the attenuated Radon transform in emission computed tomography.A least-squares method was adopted to reconstruct a 2D vector field from directional projection measurements. Attenuated projections of only the longitudinal projections of the vector field were simulated. The components of the vector field were reconstructed using the gradient algorithm to minimize a least-squares criterion. This result was compared with the reconstruction of longitudinal projections of the vector field without attenuation. Ifattenuation is known, the algorithm was able to accurately reconstruct both components of the full vector field from only one set of directional projection measurements. A better reconstruction was obtained with attenuation than without attenuation implying that attenuation provides important information for the reconstruction of flow vector fields.This confirms previous work where we showed that knowledge of the attenuation distribution helps in the reconstruction of MRI diffusion tensor fields from fewer than the required measurements. In the application of ultrasound the attenuation distribution is obtained with pulse wave transmission computed tomography and flow information is obtained with continuous wave Doppler.
Conformal Killing vector fields and a virial theorem
José F. Cariñena; Irina Gheorghiu; Eduardo Martínez; Patrícia Santos
2014-10-08
The virial theorem is formulated both intrinsically and in local coordinates for a Lagrangian system of mechanical type on a Riemann manifold. An import case studied in this paper is that of an affine virial function associated to a vector field on the configuration manifold. The special cases of a virial function associated to a Killing, a homothetic and a conformal Killing vector field are considered and the corresponding virial theorems are established for this type of functions.
Conformal Killing vector fields and a virial theorem
NASA Astrophysics Data System (ADS)
Cariñena, José F.; Gheorghiu, Irina; Martínez, Eduardo; Santos, Patrícia
2014-11-01
The virial theorem is formulated both intrinsically and in local coordinates for a Lagrangian system of a mechanical type on a Riemann manifold. An important case studied in this paper is that of an affine virial function associated with a vector field on the configuration manifold. The special cases of a virial function associated with a Killing, a homothetic, and a conformal Killing vector field are considered and the corresponding virial theorems are established for these types of functions.
Vector Field Visual Data Analysis Technologies for Petascale Computational Science
Garth, Christoph; Deines, Eduard; Joy, Kenneth I.; Bethel, E. Wes; Childs, Hank; Weber, Gunther; Ahern, Sean; Pugmire, Dave; Sanderson, Allen; Johnson, Chris
2009-11-13
State-of-the-art computational science simulations generate large-scale vector field data sets. Visualization and analysis is a key aspect of obtaining insight into these data sets and represents an important challenge. This article discusses possibilities and challenges of modern vector field visualization and focuses on methods and techniques developed in the SciDAC Visualization and Analytics Center for Enabling Technologies (VACET) and deployed in the open-source visualization tool, VisIt.
Evolution of magnetic field inclination in a forming penumbra
NASA Astrophysics Data System (ADS)
Jur?ák, Jan; Bello González, Nazaret; Schlichenmaier, Rolf; Rezaei, Reza
2014-12-01
As a sunspot penumbra forms, the magnetic field vector at the outer boundary of the protospot undergoes a transformation. We study the changes of the magnetic field vector at this boundary as a penumbral segment forms. We analyze a set of spectropolarimetric maps covering 2 hr during the formation of a sunspot in NOAA 11024. The data were recorded with the GFPI instrument attached to the German VTT. We observe a stationary umbra/quiet Sun boundary, where the magnetic field becomes more horizontal with time. The magnetic field inclination increases by 5°, reaching a maximum value of about 59°. The maximum inclination coincides with the onset of filament formation. In time, the penumbra filaments become longer and the penumbral bright grains protrude into the umbra, where the magnetic field is stronger and more vertical. Consequently, we observe a decrease in the magnetic field inclination at the boundary as the penumbra grows. In summary, in order to initiate the formation of the penumbra, the magnetic field at the umbral (protospot) boundary becomes more inclined. As the penumbra grows, the umbra/penumbra boundary migrates inwards, and at this boundary the magnetic field turns more vertical again, while it remains inclined in the outer penumbra.
Magnetic Resonance Imaging of time-varying magnetic fields from therapeutic devices
Hernandez-Garcia, Luis; Bhatia, Vivek; Prem-Kumar, Krishan; Ulfarsson, Magnus
2013-01-01
While magnetic resonance imaging of static magnetic fields generated by external probes has been previously demonstrated, there is an unmet need to image time-varying magnetic fields, such as those generated by transcranial magnetic stimulators or radiofrequency hyperthermia probes. A method to image such time-varying magnetic fields is introduced in this work. This article presents the theory behind the method and provides proof of concept by imaging time-varying magnetic fields generated by a figure-eight coil inside simple phantoms over a range of frequencies and intensities, using a 7T small animal MRI scanner. The method is able to reconstruct the three-dimensional components of the oscillating magnetic field vector. PMID:23355446
Analytical calculation of the magnetic field produced by electric power lines
George Filippopoulos; Dimitris Tsanakas
2005-01-01
The magnetic field produced by electric power lines is usually calculated numerically with the use of a computer. However, the analytical calculation of the magnetic field is preferable because it results in a mathematical expression for showing its dependences on the various parameters of the line arrangement. A method to derive the analytical formula of the magnetic field vector produced
Determining the Geographical Attitude in Iran Using Global Model of Earth's Magnetic Field
Kaveh Kianfar; Ehsan Darabi; Arefeh Moridi; Reza Amiri
2011-01-01
Determining the attitude and position in magnetic field of the earth is considered as main method in the future of passive navigation. This paper aims to extract a model for determining the situation in Iran using earth's magnetic field vector. The proposed method uses the reverse of global model of earth's magnetic field. To make the model and its relation
Vector Field Induced Chaos in Multi-dimensional Homogeneous Cosmologies
Riccardo Benini; Alexander A. Kirillov; Giovanni Montani
2007-01-16
We show that in multidimensional gravity vector fields completely determine the structure and properties of singularity. It turns out that in the presence of a vector field the oscillatory regime exists for any number of spatial dimensions and for all homogeneous models. We derive the Poincar\\'e return map associated to the Kasner indexes and fix the rules according to which the Kasner vectors rotate. In correspondence to a 4-dimensional space time, the oscillatory regime here constructed overlap the usual Belinski-Khalatnikov-Liftshitz one.
Early SDO/HMI Magnetic Field Observations (Invited)
NASA Astrophysics Data System (ADS)
Hoeksema, J. T.; Hmi Magnetic Field Team
2010-12-01
Solar magnetic features no longer have any expectation of privacy and understanding the Sun’s magnetic field is the key to space weather prediction. The Helioseismic and Magnetic Imager on the Solar Dynamics Observatory measures polarized line profiles that measure both line-of-sight and vector magnetic fields in the photosphere. The longitudinal field is measured every 45 seconds with filtergrams from the same camera used to determine the velocity. The Stokes parameters are calculated from a longer sequence taken with a second 4096 x 4096 CCD. Inversion and disambiguation provide an estimate of the vector magnetic field components and uncertainties at least every 12 minutes in active regions. Full disk synoptic observations began in April and magnetograms are available shortly after they are observed from jsoc.stanford.edu along with a plethora of other useful magnetic field products. The low-noise line-of-sight measurements compare favorably with MDI and GONG. The vector field is being compared with other observations and appears quite stable, even in small strong-field concentrations outside of active regions. Scattered light is low and the sensitivity is very good. HMI observes the entire disk all of the time, so any feature of interest can be tracked during its entire disk passage without interruption. Knowing the detailed time development will lead to better understanding of energy storage and release in the atmosphere above and what leads to the spectacular events detected by AIA, EVE, and other instruments.
Robust Morse decompositions of piecewise constant vector fields.
Szymczak, Andrzej; Zhang, Eugene
2012-06-01
In this paper, we introduce a new approach to computing a Morse decomposition of a vector field on a triangulated manifold surface. The basic idea is to convert the input vector field to a piecewise constant (PC) vector field, whose trajectories can be computed using simple geometric rules. To overcome the intrinsic difficulty in PC vector fields (in particular, discontinuity along mesh edges), we borrow results from the theory of differential inclusions. The input vector field and its PC variant have similar Morse decompositions. We introduce a robust and efficient algorithm to compute Morse decompositions of a PC vector field. Our approach provides subtriangle precision for Morse sets. In addition, we describe a Morse set classification framework which we use to color code the Morse sets in order to enhance the visualization. We demonstrate the benefits of our approach with three well-known simulation data sets, for which our method has produced Morse decompositions that are similar to or finer than those obtained using existing techniques, and is over an order of magnitude faster. PMID:21747131
Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C
2015-05-22
Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data. PMID:25953822
Low-altitude magnetic field measurements by MESSENGER reveal Mercury’s ancient crustal field
NASA Astrophysics Data System (ADS)
Johnson, Catherine L.; Phillips, Roger J.; Purucker, Michael E.; Anderson, Brian J.; Byrne, Paul K.; Denevi, Brett W.; Feinberg, Joshua M.; Hauck, Steven A.; Head, James W.; Korth, Haje; James, Peter B.; Mazarico, Erwan; Neumann, Gregory A.; Philpott, Lydia C.; Siegler, Matthew A.; Tsyganenko, Nikolai A.; Solomon, Sean C.
2015-05-01
Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury’s crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury’s history. Ancient field strengths that range from those similar to Mercury’s present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury’s crust inferred from MESSENGER elemental composition data.
Turolla, R
2013-01-01
It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these `magnetar candidates' exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (~4.4E+13 G). The recent discovery of fully-qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.
NASA Astrophysics Data System (ADS)
Turolla, Roberto; Esposito, Paolo
2013-11-01
It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (? 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.
Primordial Magnetic Fields in Cosmology
Iain A. Brown
2008-12-09
Magnetic fields have been observed in galaxies, clusters of galaxies and probably in superclusters. While mechanisms exist to generate these in the late universe, it is possible that magnetic fields have existed since very early times. This thesis is concerned with methods to predict the form of such imprints. We review in detail a standard, linearised cosmology before introducing an electromagnetic field. We then consider the intrinsic statistics of the magnetic stresses in two ways, analytically and via static realisations. We construct the power spectra, some of which we present for the first time. At the one- and three-point level we find significant intrinsic non-Gaussianities. Finally we turn to the observable impacts a primordial magnetic field. Assuming coherence, the statistics of the source can be mapped onto the CMB in a simple manner. We demonstrate that our approach is valid by reproducing the signals for Gaussian power law fields on the microwave sky. [ABRIDGED
The Cassini Magnetic Field Investigation
M. K. Dougherty; S. Kellock; D. J. Southwood; A. Balogh; E. J. Smith; B. T. Tsurutani; B. Gerlach; K.-H. Glassmeier; F. Gleim; C. T. Russell; G. Erdos; F. M. Neubauer; S. W. H. Cowley
2004-01-01
The dual technique magnetometer system onboard the Cassini orbiter is described. This instrument consists of vector helium and fluxgate magnetometers with the capability to operate the helium device in a scalar mode. This special mode is used near the planet in order to determine with very high accuracy the interior field of the planet. The orbital mission will lead to
Unveiling locally linearly polarized vector fields with broken axial symmetry
Wang Xilin; Lou Kai; Chen Jing; Gu Bing; Li Yongnan [School of Physics and Key Laboratory of Weak Light Nonlinear Photonics, Nankai University, Tianjin 300071 (China); Wang Huitian [School of Physics and Key Laboratory of Weak Light Nonlinear Photonics, Nankai University, Tianjin 300071 (China); Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093 (China)
2011-06-15
We explore how the focusing of axial-symmetry-broken vector fields is associated with a sector aperture whose apex coincides with the field axis. Its focused field is azimuthally split into a pair of orthogonal right- and left-handed circularly polarized partial rings which are rotated by angles of {+-}{pi}/2 with respect to the input vector field carrying no orbital angular momentum (OAM) and no spin angular momentum (SAM), respectively. Each member of the pair of partial rings carries not only the opposite OAM but also the opposite SAM. We unveil the underlying physics behind such an effect.
Full vector spherical harmonic analysis of the Holocene geomagnetic field
NASA Astrophysics Data System (ADS)
Richardson, Marcia
High-quality time-series paleomagnetic measurements have been used to derive spherical harmonic models of Earth's magnetic field for the past 2,000 years. A newly-developed data compilation, PSVMOD2.0 consists of time-series directional and intensity records that significantly improve the data quality and global distribution used to develop previous spherical harmonic models. PSVMOD2.0 consists of 185 paleomagnetic time series records from 85 global sites, including 30 full-vector records (inclination, declination and intensity). It includes data from additional sites in the Southern Hemisphere and Arctic and includes globally distributed sediment relative paleointensity records, significantly improving global coverage over previous models. PSVMOD2.0 records have been assessed in a series of 7 regional intercomparison studies, four in the Northern Hemisphere and 3 in the southern hemisphere. Comparisons on a regional basis have improved the quality and chronology of the data and allowed investigation of spatial coherence and the scale length associated with paleomagnetic secular variation (PSV) features. We have developed a modeling methodology based on nonlinear inversion of the PSVMOD2.0 directional and intensity records. Models of the geomagnetic field in 100-year snapshots have been derived for the past 2,000 with the ultimate goal of developing models spanning the past 8,000 years. We validate the models and the methodology by comparing with the GUFM1 historical models during the 400-year period of overlap. We find that the spatial distribution of sites and quality of data are sufficient to derive models that agree with GUFM1 in the large-scale characteristics of the field. We use the the models derived in this study to downward continue the field to the core-mantle boundary and examine characteristics of the large-scale structure of the magnetic field at the source region. The derived models are temporally consistent from one epoch to the next and exhibit many of the expected characteristics of the field over time (high-latitude flux lobes, South Atlantic reverse flux patch, north pole reverse or null flux region).
Investigating Magnetic Force Fields
NSDL National Science Digital Library
Daryl ("Tish") Monjeau, Bancroft Elementary School, Minneapolis, MN
2012-03-18
In this classroom activity, the students will investigate the magnetic pull of a bar magnet at varying distances with the use of paper clips. Students will hypothesize, conduct the experiment, collect the data, and draw conclusions that support their data. Each student will record the experiment and their findings in their science journals. As a class, students will compare each groups' data and their interpretation of the results.
Magnetic field properties of the ISABELLE Project superconducting dipole magnets
Kirk, H.G.; Engelmann, R.; Herrera, J.; Jaeger, K.; Robins, K.; Willen, E.
1981-01-01
A series of prototype superconducting dipole magnets have been constructed and tested as part of the ISABELLE Project research and development program. Results of magnetic field measurements are presented with emphasis placed on the DC and AC components of the main field. Magnetization and the effects of the magnetic fields at the ends of the magnet are displayed.
Gauge Fields, Membranes, and Subdeterminant Vector Models
Leigh, Robert G.; Mauri, Andrea; Minic, Djordje; Petkou, Anastasios C. [Department of Physics, University of Illinois, 1110 West Green Street, Urbana, Illinois 61801 (United States); Dipartimento di Fisica Teorica, Universita degli Studi di Milano, Via Celoria, Milano 20133 (Italy); IPNAS, Department of Physics, Virginia Tech, Blacksburg, Virginia 24061 (United States); Department of Physics, University of Crete, GR-71003, Heraklion (Greece)
2010-06-04
We present a class of classically marginal N-vector models in d=4 and d=3 whose scalar potentials can be written as subdeterminants of symmetric matrices. The d=3 case can be thought of as a generalization of the scalar sector of the Bagger-Lambert-Gustavsson model. Using the Hubbard-Stratonovich transformation we calculate their effective potentials which exhibit intriguing large-N scaling behaviors. We comment on the possible relevance of our models to strings, membranes, and also to a class of novel spin systems that are based on ternary commutation relations.
Measuring Earth's Magnetic Field Simply.
ERIC Educational Resources Information Center
Stewart, Gay B.
2000-01-01
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)
NASA Technical Reports Server (NTRS)
Ness, N. F.
1977-01-01
The Mariner 10 spacecraft encountered Mercury three times in 1974-1975. The first and third encounters provided detailed observations of a well-developed detached bow shock wave which results from the interaction of the solar wind. The planet possesses a global magnetic field and a modest magnetosphere, which deflects the solar wind. The field is approximately dipolar, with orientation in the same sense as earth, tilted 12 deg from the rotation axis. The magnetic moment corresponds to an undistorted equatorial field intensity of 350 gammas, approximately 1% of earth's. The field, while unequivocally intrinsic to the planet, may be due to remanent magnetization acquired from an extinct dynamo or a primordial magnetic field or due to a presently active dynamo. The latter possibility appears more plausible at present. In any case, the existence of the magnetic field provides very strong evidence of a mature differentiated planetary interior with a large core (core radius about 0.7 Mercury radius) and a record of the history of planetary formation in the magnetization of the crustal rocks.
Optical sensor of magnetic fields
Butler, M.A.; Martin, S.J.
1986-03-25
An optical magnetic field strength sensor for measuring the field strength of a magnetic field comprising a dilute magnetic semi-conductor probe having first and second ends, longitudinally positioned in the magnetic field for providing Faraday polarization rotation of light passing therethrough relative to the strength of the magnetic field. Light provided by a remote light source is propagated through an optical fiber coupler and a single optical fiber strand between the probe and the light source for providing a light path therebetween. A polarizer and an apparatus for rotating the polarization of the light is provided in the light path and a reflector is carried by the second end of the probe for reflecting the light back through the probe and thence through the polarizer to the optical coupler. A photo detector apparatus is operably connected to the optical coupler for detecting and measuring the intensity of the reflected light and comparing same to the light source intensity whereby the magnetic field strength may be calculated.
Primordial Magnetic Fields and Causality
Ruth Durrer; Chiara Caprini
2003-10-29
We discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much more suppressed than usually assumed and that a helical component is even more reduced. Due to this strong suppression, even maximal primordial fields generated at the electroweak phase transition can just marginally seed the fields in clusters, but they cannot leave any detectable imprint on the cosmic microwave background.
Magnetically-Responsive Nanoparticles for Vectored Delivery of Cancer Therapeutics
NASA Astrophysics Data System (ADS)
Klostergaard, Jim; Bankson, James; Woodward, Wendy; Gibson, Don; Seeney, Charles
2010-12-01
We propose that physical targeting of therapeutics to tumors using magnetically-responsive nanoparticles (MNPs) will enhance intratumoral drug levels compared to free drugs in an effort to overcome tumor resistance. We evaluated the feasibility of magnetic enhancement of tumor extravasation of systemically-administered MNPs in human xenografts implanted in the mammary fatpads of nude mice. Mice with orthotopic tumors were injected systemically with MNPs, with a focused magnetic field juxtaposed over the tumor. Magnetic resonance imaging and scanning electron microscopy both indicated successful tumor localization of MNPs. Next, MNPs were modified with poly-ethylene-glycol (PEG) and their clearance compared by estimating signal attenuation in liver due to iron accumulation. The results suggested that PEG substitution could retard the rate of MNP plasma clearance, which may allow greater magnetically-enhanced tumor localization. We propose that this technology is clinically scalable to many types of both superficial as well as some viscerable tumors with existing magnetic technology.
Magnetic field induced dynamical chaos
Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra, E-mail: bidhanchandra.bag@visva-bharati.ac.in [Department of Chemistry, Visva-Bharati, Santiniketan 731 235 (India)
2013-12-15
In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.
PROTOSTELLAR DISK FORMATION ENABLED BY WEAK, MISALIGNED MAGNETIC FIELDS
Krumholz, Mark R. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Crutcher, Richard M. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801 (United States); Hull, Charles L. H., E-mail: mkrumhol@ucsc.edu [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States)
2013-04-10
The gas from which stars form is magnetized, and strong magnetic fields can efficiently transport angular momentum. Most theoretical models of this phenomenon find that it should prevent formation of large (>100 AU), rotationally supported disks around most protostars, even when non-ideal magnetohydrodynamic (MHD) effects that allow the field and gas to decouple are taken into account. Using recent observations of magnetic field strengths and orientations in protostellar cores, we show that this conclusion is incorrect. The distribution of magnetic field strengths is very broad, and alignments between fields and angular momentum vectors within protostellar cores are essentially random. By combining the field strength and misalignment data with MHD simulations showing that disk formation is expected for both weak and misaligned fields, we show that these observations imply that we should expect disk fractions of {approx}10%-50% even when protostars are still deeply embedded in their parent cores, and even if the gas is governed by ideal MHD.
Computation of Surface Integrals of Curl Vector Fields
ERIC Educational Resources Information Center
Hu, Chenglie
2007-01-01
This article presents a way of computing a surface integral when the vector field of the integrand is a curl field. Presented in some advanced calculus textbooks such as [1], the technique, as the author experienced, is simple and applicable. The computation is based on Stokes' theorem in 3-space calculus, and thus provides not only a means to…
ON THE DISTRIBUTIONAL DIVERGENCE OF VECTOR FIELDS VANISHING AT INFINITY
De Pauw, Thierry - Institut de MathÃ©matiques de Jussieu, UniversitÃ© Paris 7
ON THE DISTRIBUTIONAL DIVERGENCE OF VECTOR FIELDS VANISHING AT INFINITY THIERRY DE PAUW AND MONICA vanishing at infinity if and only if F acts linearly on BV m m-1 (Rm) (the space of functions in L m m-1 (Rm field, vanishing at infinity, v C0(Rm ; Rm ) such that div v = f weakly. In fact we characterize those
A chargeless complex vector matter field in supersymmetric scenario
L. P. Colatto; A. L. A. Penna
2014-10-14
In this paper we construct and study a formulation of a chargeless complex vector matter field in a supersymmetric framework. To this aim we combine two no-chiral scalar superfields in order to take the vector component field to build the chargeless complex vector superpartner where the respective field strength transforms as matter fields by a global $U(1)$ gauge symmetry. To the aim to deal with consistent terms without breaking the global $U(1)$ symmetry it imposes a choice to the complex combination revealing a kind of symmetry between the choices and eliminate the extra degrees of freedom consistently with the supersymmetry. As the usual case the mass supersymmetric sector contributes as a complement to dynamics of the model. We obtain the equations of motion of the Proca's type field, for the chiral spinor fields and for the scalar field on the mass-shell which show the same mass as expected. This work establishes the firsts steps to extend the analysis of charged massive vector field in a supersymmetric scenario.
Safety concerns related to magnetic field exposure
Amanda K. Andriola Silva; Érica L. Silva; E. Sócrates T. Egito; Artur S. Carriço
2006-01-01
The recent development of superconducting magnets has resulted in a huge increase in human exposure to very large static magnetic fields of up to several teslas (T). Considering the rapid advances in applications and the great increases in the strength of magnetic fields used, especially in magnetic resonance imaging, safety concerns about magnetic field exposure have become a key issue.
Chromospheric magnetic fields of an active region filament
NASA Astrophysics Data System (ADS)
Xu, Z.; Solanki, S.; Lagg, A.
2012-06-01
Vector magnetic fields of an active region filament are co-spatially and co-temporally mapped in photosphere and upper chromosphere, by using spectro-polarimetric observations made by Tenerife Infrared Polarimeter (TIP II) at the German Vacuum Tower Telescope (VTT). A Zeeman-based ME inversion is performed on the full Stokes vectors of both the photospheric Si I 1082.7 nm and the chromospheric He I 1083.0 nm lines. We found that the strong magnetic fields, with the field strength of 600 - 800 G in the He I line formation height, are not uncommon among AR filaments. But such strong magnetic field is not always found in AR filaments.
Electric and magnetic field exposure
S. S. Sussman
1988-01-01
The possible health hazards of low-level, power line frequency (50\\/60 Hz) electric and magnetic fields are considered. The historical background to this concern is briefly discussed. The types of studies being carried out and the results so far are summarized. It is concluded that while the scientific evidence on field effects is inconclusive, inferences of health effects justify further evaluation
A non-linear coupled 3D model for magnetic field and electric circuit equations
F. Piriou; A. Razek
1992-01-01
The authors propose a 3-D numerical model in which the magnetic field and electric circuit equations in the absence of eddy currents are solved simultaneously. To consider the magnetic equations, use is made of a magnetic vector potential formulation with the gauge condition (A.w=0) which makes it possible to reduce the number of unknowns. To take into account the magnetic
Formation of Non-Potential Magnetic Field and Flare-CMEs Eruption
Hongqi Zhang
2005-01-01
We analyze the formation process of delta configuration in some well-known super active regions based on the photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows the potential-like configuration in the solar atmosphere, the magnetic shear develops mainly near the magnetic neutral line with the magnetic islands
Magnetic fields and coronal heating
NASA Technical Reports Server (NTRS)
Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S.
1980-01-01
General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size.
Magnetic fields in neutron stars
NASA Astrophysics Data System (ADS)
Viganò, Daniele
2013-09-01
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.
MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.
JAIN, A.; ESCALLIER, J.; GANETIS, G.; LOUIE, W.; MARONE, A.; THOMAS. R.; WANDERER, P.
2004-10-03
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.
Self Magnetic Field and Current-loop of Electron with Five Different Radii and Intrinsic Properties
S. Ghosh; M. R. Devi; A. Choudhury; J. K. Sarma
2009-01-01
With the rotation of charge in a circular path current-loop is generated. This results in the production of magnetic fields in a charged body. This self (internal) magnetic field is treated here with five different radii of electron. Closed loop line integral of magnetic induction vector or the integral form of the Ampere's circuital law is expressed in terms intrinsic
hal-00009182,version3-7Sep2007 KILLING VECTOR FIELDS WITH TWISTOR DERIVATIVE
Paris-Sud XI, Université de
hal-00009182,version3-7Sep2007 KILLING VECTOR FIELDS WITH TWISTOR DERIVATIVE ANDREI MOROIANU give the complete classification of compact Riemannian manifolds carrying a Killing vector field whose: Primary 53C55, 58J50. Keywords: Killing vector fields, twistor forms, gradient conformal vector fields. 1
Vector Field Design on Surfaces Eugene Zhang, Konstantin Mischaikow and Greg Turk
Mischaikow, Konstantin
Vector Field Design on Surfaces Eugene Zhang, Konstantin Mischaikow and Greg Turk Georgia Institute of Technology Vector field design on surfaces is necessary for many graphics applications: example-based texture contained in the input vector field often cause visual artifacts. In this paper, we present a vector field
Solar Polarimetry and Magnetic Field Measurements
NASA Astrophysics Data System (ADS)
del Toro Iniesta, J. C.
2001-05-01
The magnetic nature of most solar (spatially resolved or unresolved) structures is amply recognized. Magnetic fields of the Sun play a paramount rôle in the overall thermodynamic and dynamic state of our star. The main observable manifestation of solar magnetic fields is the polarization of light either through the Zeeman effect on spectral lines or through the Hanle effect (depolarization by very weak magnetic fields of light previously polarized by scattering). Hence, one can easily understand the increasing importance that polarimetry is experimenting continuously in solar physics. Under the title of this contribution a six-hour course was given during the summer school. Clearly, the limited extension allocated for the notes in these proceedings avoids an extensive account of the several topics discussed: 1) a description of light as an electromagnetic wave and the polarization properties of monochromatic, time-harmonic, plane waves; 2) the polarization properties of polychromatic light and, in particular, of quasi-monochromatic light; 3) the transformations of (partially) polarized light by linear optical systems and a description of the ways we measure the Stokes parameters by spatially and/or temporally modulating the polarimetric signal; 4) a discussion on specific problems relevant to solar polarimetry like seeing-induced and instrumental polarization, or modulation and demodulation, along with a brief description of current solar polarimeters; 5) the vector radiative transfer equation for polarized light and its links to the scalar one for unpolarized light, together with a summary of the Zeeman effect and its consequences on line formation in a magnetized stellar atmosphere; 7) an introduction of the paramount astrophysical problem, i.e., that of finding diagnostics that enable the solar physicist to interpret the observables in terms of the solar atmospheric quantities, including a discussion on contribution and response functions; and 8) a brief outline of inversion techniques as a recommended way to infer values of the vector magnetic field and other thermodynamic and dynamic quantities. Since most of the material presented in the lectures can be found in the literature, I decided to focus these pages to those topics that, in my opinion, need a particular stress and/or do not have received much attention in previous reviews or textbooks. These notes have been written with mostly didactical purposes so that, skipping the customary usage, just a few references will be cited within the text. Instead, a classified (and necessarily incomplete) bibliography is recommended at the end.
NASA Astrophysics Data System (ADS)
Wakabayashi, Daisuke; Todaka, Takashi; Enokizono, Masato
This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional magnetostriction in non-oriented and grain-oriented silicon steel sheets are compared.
Daisuke Wakabayashi; Takashi Todaka; Masato Enokizono
2010-01-01
This paper presents measured magnetostriction of electrical steel sheets under alternating magnetic flux conditions. In the measurements, we used a two-dimensional vector magnetic property measurement system, and a three-axial strain gauge. In order to know magnetostrictions in arbitrary direction, the strain tensor was evaluated. In addition, we try to evaluate the magnetostrictions in thickness direction. In this paper, the three-dimensional
Full-vector archeomagnetic and rock-magnetic results from Portuguese kilns
NASA Astrophysics Data System (ADS)
Gomez-Paccard, Miriam; Tema, Evdokia; McIntosh, Gregg; Letaio, Manuela; Calado, Marco; Botelho, Paulo
2014-05-01
Despite the increase in archeomagnetic studies in the past few years, the number of reliable archeointensity data is still limited. At present Europe is the most widely covered region, although the variation in geomagnetic field intensity is not completely known for the last millennia and the occurrence and behaviour of various rapid geomagnetic field changes is under discussion. In this context, new high-reliable full-geomagnetic field vector determinations from unexplored regions are crucial in order to improve our knowledge of past geomagnetic field changes at regional scales. In Portugal, despite the rich cultural heritage and the abundance of archaeological excavations, archaeomagnetic research is still in its infancy. To our knowledge, up to now the only available directional data obtained from more or less well-dated materials come from the study of a Late Bronze Age vitrified wall close to the city of Serpa, southern Portugal, while only two more studies have been published including archaeointesity results from Portuguese pottery. We present here the first full-vector archeomagnetic results (declination, inclination and intensity) from two kilns excavated at two archaeological sites at Lisboa (Portugal). The first structure corresponds to the Largo das Alcaçarias Islamic pottery production workshop located in the eastern suburb Luxbona (current Alfama) and its abandonment has been dated as the 12th century AD. The second kiln was excavated in the Encosta Santana archeological medieval site and was abandoned during the 12th or 13th centuries AD according to archeological evidence. Detailed archaeomagnetic and rock magnetic studies have been carried out in order to determine the magnetic mineralogy and investigate the thermal stability of the phases carrying the archaeomagnetic signal. Both kilns exhibited thermally stability magnetic phases. The magnetic properties of the Largo kiln are dominated by a mixture of magnetite/cation-substituted magnetite and cation-substituted hematite. Those of the Encosta kiln are dominated by magnetite with limited cation substitution, with hysteresis ratios falling close to the single domain - multidomain unmixing curve of Dunlop. The new archeomagnetic and rock-magnetic data are based on the study of several samples per kiln and the archeointensity determinations were obtained using the Thellier classical method with regular partial thermoremanent magnetization (pTRM) checks and TRM anisotropy and cooling rate corrections. From the laboratory experiments, two new high quality mean intensities are now available for Portugal. The new data are the first full-vector results from Portuguese kilns. They significantly contribute to better understand the secular variation of the Earth's magnetic field in western Europe during the 12-13th centuries AD and can be used as reliable input data for geomagnetic field modelling.
Magnetic shielding by soft magnetic materials in alternating magnetic field
Yasuo Okazaki; Kiyoshi Ueno
1992-01-01
The magnetic shielding effect of an alternating field up to 20 kHz was examined in 3% Si steel sheets and amorphous ribbons. Not only the permeability but also the domain configuration was found to affect the shielding effects. The annealed Fe-based amorphous shield without field showed exceedingly high shielding effectiveness for higher frequencies.
Magnetic field structure generation in collisional dusty plasmas
Padma Kant Shukla; Fernando Haas
2008-01-01
A perpendicular ion drift is proposed as a possible mechanism for the generation of magnetic field structures in a highly collisional dusty plasma. The basic dissipation mechanism is assumed to be the dust-neutral momentum exchange, so that plasmas with a small ionization fraction are natural candidates for experiments. The model reduces to a nonlinear partial differential equation for the vector
Spacecraft attitude determination using the earth's magnetic field
NASA Technical Reports Server (NTRS)
Simpson, David G.
1989-01-01
A method is presented by which the attitude of a low-Earth orbiting spacecraft may be determined using a vector magnetometer, a digital Sun sensor, and a mathematical model of the Earth's magnetic field. The method is currently being implemented for the Solar Maximum Mission spacecraft (as a backup for the failing star trackers) as a way to determine roll gyro drift.
Theorem on magnet fringe field
Jie Wei; R. Talman
1995-01-01
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} + iBâ = â(b{sub n} + ia{sub n})(x + iy)â¿, where x, y, and z denote horizontal, vertical, and longitudinal (along the
Topology based visualization for vector and tensor fields
NASA Astrophysics Data System (ADS)
Lavin, Yingmei
1998-12-01
Vector and second-order tensor fields have important applications in many science and engineering disciplines. Yet, due to their multivariate, multidimensional nature, they are typically very difficult to comprehend. The usefulness of topology based visualization is in its simplistic representation while maintaining the richness of the data set. Much research has been accomplished on vector field visualization. However, virtually none is on quantitative comparisons of similarities and differences between vector fields. In this dissertation, a novel approach is introduced to define a topology based measurement for such a purpose. This new measure relies on the use of critical points, which are a key feature in vector field topology. A technique known as Earth Mover's Distance is used to compute the closeness between various pairs of vector fields, and a nearest neighbor query is thus produced to illustrate the relationship between the given set of vector fields. The usefulness of this measurement can be seen when comparing computational and experimental flow fields under the same conditions. Furthermore, its applicability can be extended to more cumbersome tasks such as navigating through a large database searching for similar topology. Very few methods have been developed to understand and visualize second-order tensor fields due to their complex nature and large data sizes. Topology based studies have been carried out in two-dimensional space. This dissertation extends the research into three dimensions, an area that hasn't been studied before. A decomposition procedure is introduced to break a tensor field into a deviator and an isotropic tensor. A deviator determines the properties of a tensor field, while the isotropic part provides a uniform bias. Degenerate points are the basic constituents of second-order tensor fields. We study control functions to shed light on the representation of degenerate points in a tensor field. The properties of the degenerate points reveal the local as well as global topological structures in a 3D tensor field. These degenerate points can further be linked to important characteristics of the underlying physical phenomena.
Observations of Mercury's magnetic field
NASA Technical Reports Server (NTRS)
Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.
1975-01-01
Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.
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
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.
NASA Technical Reports Server (NTRS)
Schuler, James J.; Felippa, Carlos A.
1991-01-01
Electromagnetic finite elements are extended based on a variational principle that uses the electromagnetic four potential as primary variable. The variational principle is extended to include the ability to predict a nonlinear current distribution within a conductor. The extension of this theory is first done on a normal conductor and tested on two different problems. In both problems, the geometry remains the same, but the material properties are different. The geometry is that of a 1-D infinite wire. The first problem is merely a linear control case used to validate the new theory. The second problem is made up of linear conductors with varying conductivities. Both problems perform well and predict current densities that are accurate to within a few ten thousandths of a percent of the exact values. The fourth potential is then removed, leaving only the magnetic vector potential, and the variational principle is further extended to predict magnetic potentials, magnetic fields, the number of charge carriers, and the current densities within a superconductor. The new element produces good results for the mean magnetic field, the vector potential, and the number of superconducting charge carriers despite a relatively high system condition number. The element did not perform well in predicting the current density. Numerical problems inherent to this formulation are explored and possible remedies to produce better current predicting finite elements are presented.
Protogalactic evolution and magnetic fields
Harald Lesch; Masashi Chiba
1994-11-17
We show that the relatively strong magnetic fields ($\\ge 1 \\mu$G) 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 "top-hat" model and tidal torque theory for the fate of a forming galaxy in an expanding universe. Very weak fields $10^{-19} \\sim 10^{-23}$G created in an expanding over-dense region are strongly enhanced due to the dissipative disk formation by a factor $\\sim 10^4$, and subsequently amplified by strong non-axisymmetric flow by a factor $\\sim 10^{6-10}$, depending on the cosmological parameters and the epoch of galaxy formation. The resulting field strength at $z \\sim 0.395$ can be of the order of a few $\\mu$G and be close to this value at $z \\sim 2$.
Krzysztof T. Chyzy
2008-02-28
The origin of asymmetric radio polarized emission and properties of magnetic fields in the Virgo Cluster spiral NGC4254 are investigated with help of "magnetic maps" presenting distributions of different magnetic field components over the entire galaxy, free of Faraday rotation and projection effects. We show that the dramatic variation of orientation of magnetic field vectors (from 0deg to more than 40deg) throughout the galaxy cannot arise from the dynamo process alone, but must be dominated by the effects like density waves and local gas flows. We determine within the galaxy the relation between the strength of total magnetic field and the local star-formation rate (SFR) as a power-law with an index of +0.18+-0.01. We find the opposite sense of relation of magnetic field regularity with SFR (-0.32+-0.03) and suggest that it results from efficient production of random field with rising turbulence in the regions with actively forming stars. The distribution of Faraday rotation measures in NGC4254 indicates a perturbed axisymmetrical mean-field dynamo mode or a mixture of axisymmetrical and bisymmetrical ones with regular field directed outwards the disk, which is contrary to most observed galaxies. The magnetic fields within two outer magnetic arms (shifted downstream of a density wave) are strong, up to 13muG in the regular field and 20muG in the total field. Our modeling of cluster influence on different magnetic field components indicates that within the outer magnetic arms the dynamo-induced magnetic fields are modified by stretching and shearing forces rather than by cluster ram pressure. Those forces, which are likely triggered by the galaxy's gravitational interaction, produce an anisotropic component of the regular field and enhance the polarized emission.(abridged)
Low-frequency fluctuations in plasma magnetic fields
Cable, S.; Tajima, T.
1992-02-01
It is shown that even a non-magnetized plasma with temperature T sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, non-magnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wavenumber is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac {delta}-function in the collisionless plasma; it is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low frequency cutoff in the typical black-body radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic field were vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes which forms the non-magnetized zero-frequency peak of the isotropic plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves if found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic field fluctuation spectrum as well. For the degenerate plasma, we find that electric field fluctuations and number density fluctuations vanish at zero frequency; however, the magnetic field power spectrum diverges at zero frequency.
Magnetic Forces and Field Line Density
NSDL National Science Digital Library
2012-08-03
This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.
Magnetic space-based field measurements
NASA Technical Reports Server (NTRS)
Langel, R. A.
1981-01-01
Because the near Earth magnetic field is a complex combination of fields from outside the Earth of fields from its core and of fields from its crust, measurements from space prove to be the only practical way to obtain timely, global surveys. Due to difficulty in making accurate vector measurements, early satellites such as Sputnik and Vanguard measured only the magnitude survey. The attitude accuracy was 20 arc sec. Both the Earth's core fields and the fields arising from its crust were mapped from satellite data. The standard model of the core consists of a scalar potential represented by a spherical harmonics series. Models of the crustal field are relatively new. Mathematical representation is achieved in localized areas by arrays of dipoles appropriately located in the Earth's crust. Measurements of the Earth's field are used in navigation, to map charged particles in the magnetosphere, to study fluid properties in the Earth's core, to infer conductivity of the upper mantels, and to delineate regional scale geological features.
Simulations of magnetic fields in filaments
M. Bruggen; M. Ruszkowski; A. Simionescu; M. Hoeft; C. Dalla Vecchia
2005-08-10
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 highly resolved cosmological AMR simulations of magnetic fields in the cosmos and make predictions about the evolution and structure of magnetic fields in filaments. Comparing our results to observational evidence for magnetic fields in filaments suggests that amplification of seed fields by gravitational collapse is not sufficient to produce IGM fields. Finally, implications for cosmic ray transport are discussed.
Origin of primordial magnetic fields
Souza, Rafael S. de; Opher, Reuven [IAG, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, CEP 05508-900, Sao Paulo, SP (Brazil)
2008-02-15
Magnetic fields of intensities similar to those in our galaxy are also observed in high redshift galaxies, where a mean field dynamo would not have had time to produce them. Therefore, a primordial origin is indicated. It has been suggested that magnetic fields were created at various primordial eras: during inflation, the electroweak phase transition, the quark-hadron phase transition (QHPT), during the formation of the first objects, and during reionization. We suggest here that the large-scale fields {approx}{mu}G, observed in galaxies at both high and low redshifts by Faraday rotation measurements (FRMs), have their origin in the electromagnetic fluctuations that naturally occurred in the dense hot plasma that existed just after the QHPT. We evolve the predicted fields to the present time. The size of the region containing a coherent magnetic field increased due to the fusion of smaller regions. Magnetic fields (MFs) {approx}10 {mu}G over a comoving {approx}1 pc region are predicted at redshift z{approx}10. These fields are orders of magnitude greater than those predicted in previous scenarios for creating primordial magnetic fields. Line-of-sight average MFs {approx}10{sup -2} {mu}G, valid for FRMs, are obtained over a 1 Mpc comoving region at the redshift z{approx}10. In the collapse to a galaxy (comoving size {approx}30 kpc) at z{approx}10, the fields are amplified to {approx}10 {mu}G. This indicates that the MFs created immediately after the QHPT (10{sup -4} s), predicted by the fluctuation-dissipation theorem, could be the origin of the {approx}{mu}G fields observed by FRMs in galaxies at both high and low redshifts. Our predicted MFs are shown to be consistent with present observations. We discuss the possibility that the predicted MFs could cause non-negligible deflections of ultrahigh energy cosmic rays and help create the observed isotropic distribution of their incoming directions. We also discuss the importance of the volume average magnetic field predicted by our model in producing the first stars and in reionizing the Universe.
Magnetic field tomography, helical magnetic fields and Faraday depolarization
NASA Astrophysics Data System (ADS)
Horellou, C.; Fletcher, A.
2014-07-01
Wide-band radio polarization observations offer the possibility to recover information about the magnetic fields in synchrotron sources, such as details of their three-dimensional configuration, that has previously been inaccessible. The key physical process involved is the Faraday rotation of the polarized emission in the source (and elsewhere along the wave's propagation path to the observer). In order to proceed, reliable methods are required for inverting the signals observed in wavelength space into useful data in Faraday space, with robust estimates of their uncertainty. In this paper, we examine how variations of the intrinsic angle of polarized emission ?0 with the Faraday depth ? within a source affect the observable quantities. Using simple models for the Faraday dispersion F(?) and ?0(?), along with the current and planned properties of the main radio interferometers, we demonstrate how degeneracies among the parameters describing the magneto-ionic medium can be minimized by combining observations in different wavebands. We also discuss how depolarization by Faraday dispersion due to a random component of the magnetic field attenuates the variations in the spectral energy distribution of the polarization and shifts its peak towards shorter wavelengths. This additional effect reduces the prospect of recovering the characteristics of the magnetic field helicity in magneto-ionic media dominated by the turbulent component of the magnetic field.
Reduced MHD in Nearly Potential Magnetic Fields
Strauss, Hank
Reduced MHD in Nearly Potential Magnetic Fields H.R. Strauss Courant Institute of Mathematical that the magnetic field is close to a potential field. The potential field can have an arbitrary three dimensional of equations have essentially the same structure. The main time dependent variables are the magnetic field
Bosonic Casimir effect in external magnetic field
NASA Astrophysics Data System (ADS)
Cougo-Pinto, M. V.; Farina, C.; Negrão, M. R.; Tort, A. C.
1999-06-01
We compute the influence of an external magnetic field on the Casimir energy of a massive charged scalar field confined between two parallel infinite plates. For this case the obtained result shows that the magnetic field inhibits the Casimir effect.
Yu. V. Bugoslavsky; A. L. Ivanov; V. A. Kovalsky; A. A. Minakov
1996-01-01
Magnetic hysteresis loops of LaSrCuO superconducting single crystals were studied by means of a vibrating sample magnetometer at T = 4.2 K. It was directly confirmed that two types of secondary maxima are present in the magnetization curves. By means of vector magnetization measurements we proved that low-field secondary maxima in tilted magnetic field are caused by the flux line
Photospheric and coronal magnetic fields
Sheeley, N.R., Jr. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))
1991-01-01
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.
Large-Scale Magnetic Field Structures and Coronal Holes on the Sun
E. I. Mogilevsky; V. N. Obridko; N. S. Shilova
1997-01-01
This paper is aimed at establishing the relationship between the large-scale magnetic fields (LSMF), coronal holes (CH), and active regions (AR) in the Sun. The LSMF structure was analyzed by calculating the vector photospheric magnetic field under a potential approximation. Synoptic maps were drawn to study the distribution of the B? field component and to isolate regions where the open
Large scale reconstruction of the solar coronal magnetic field
NASA Astrophysics Data System (ADS)
Amari, T.; Aly, J.-J.; Chopin, P.; Canou, A.; Mikic, Z.
2014-10-01
It is now becoming necessary to access the global magnetic structure of the solar low corona at a large scale in order to understand its physics and more particularly the conditions of energization of the magnetic fields and the multiple connections between distant active regions (ARs) which may trigger eruptive events in an almost coordinated way. Various vector magnetographs, either on board spacecraft or ground-based, currently allow to obtain vector synoptic maps, composite magnetograms made of multiple interactive ARs, and full disk magnetograms. We present a method recently developed for reconstructing the global solar coronal magnetic field as a nonlinear force-free magnetic field in spherical geometry, generalizing our previous results in Cartesian geometry. This method is implemented in the new code XTRAPOLS, which thus appears as an extension of our active region scale code XTRAPOL. We apply our method by performing a reconstruction at a specific time for which we dispose of a set of composite data constituted of a vector magnetogram provided by SDO/HMI, embedded in a larger full disk vector magnetogram provided by the same instrument, finally embedded in a synoptic map provided by SOLIS. It turns out to be possible to access the large scale structure of the corona and its energetic contents, and also the AR scale, at which we recover the presence of a twisted flux rope in equilibrium.
Hamiltonian quantization of effective Lagrangians with massive vector fields
Carsten Grosse-Knetter
1993-01-01
Effective Lagrangians containing arbitrary interactions of massive vector fields are quantized within the Hamiltonian path-integral formalism. It is proven that the correct Hamiltonian quantization of these models yields the same result as naive Lagrangian quantization (Matthew's theorem). This theorem holds for models without gauge freedom as well as for (linearly or nonlinearly realized) spontaneously broken gauge theories. The Stueckelberg formalism,
Human Skin Simulation by Generating Wrinkles along Vector Fields
Human Skin Simulation by Generating Wrinkles along Vector Fields by Yosuke Bando A Senior Thesis human bodies is quality of skin. To improve this, it is necessary to represent small wrinkles on skin of Computer Graphics. 3 #12;Contents 1 Introduction 4 2 Topography of skin surface 6 3 Skin surface modeling 7
A Simple Method to Approximate the Magnetic Field in the Vicinity of Overhead Power Lines
Gabriele Grandi
The magnetic field generated by overhead power lines is usually evaluated by the Biot-Savart's law, considering a vector superposition of single straight current contribu- tions to obtain the overall rms field. This procedure is rather simple but the related calculations are rather com- plex, involving a composition of both vector and phasor quantities. In this paper a simple and general
How to Draw Magnetic Fields - I
NSDL National Science Digital Library
2012-08-03
This is an activity about depicting magnetic fields. Learners will observe two provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines for both orientations. This is the third activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.
EXPLORER 10 MAGNETIC FIELD MEASUREMENTS
J. P. Heppner; N. F. Ness; C. S. Scearce; T. L. Skillman
1963-01-01
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
G. V. Rudenko
2001-01-01
This paper is concerned with the Laplace boundary-value problem with the directional derivative, corresponding to the specific nature of measurements of the longitudinal component of the photospheric magnetic field. The boundary conditions are specified by a distribution on the sphere of the projection of the magnetic field vector into a given direction, i.e., they exactly correspond to the data of
Transverse Magnetic Field Propellant Isolator
NASA Technical Reports Server (NTRS)
Foster, John E.
2000-01-01
An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.
Levin, Michael
Levin and Ernst, DC Magnetic Field Effects on Development Applied DC Magnetic Fields Cause urchin, static magnetic field, gastrulation, development, mitotic cycle, teratogenic effects running title: static Magnetic Field Effects on Development #12;Levin and Ernst, DC Magnetic Field Effects
Hierarchal scalar and vector tetrahedra
J. P. Webb; B. Forgahani
1993-01-01
A novel set of scalar and vector tetrahedral finite elements are presented. The elements are hierarchical, allowing mixing of polynomial orders. Scalar orders up to three and vector orders up to two are defined. The vector elements impose tangential continuity on the field but not normal continuity, making them suitable for representing the vector electric or magnetic field. The scalar
A survey of long term interplanetary magnetic field variations
NASA Technical Reports Server (NTRS)
King, J. H.
1975-01-01
Interplanetary magnetic field data from 10 IMP, AIMP, and HEOS spacecraft were merged into a composite data set spanning 1963 to 1974. A consideration of the mutual consistency of the individual data sets reveals agreement typically to within 0.2 gamma. Composite data set analysis reveals: (1) whereas the yearly averaged magnitudes of all field vectors show virtually no solar cycle variation, the yearly averaged magnitudes of positive- and negative-polarity field vectors show separate solar cycle variations, consistent with variations in the average azimuthal angles of positive- and negative-polarity field vectors, (2) there is no heliolatitude dependence of long time average field magnitudes, (3) field vectors parallel to the earth-sun line are on the average 1 gamma less in magnitude than field vectors perpendicular to this line, and (4) the heliolatitude-dependent dominant polarity effect exhibits a complex sign reversal in the 1968 to 1971 period and a measure of symmetry in 1972 to 1974 not found in earlier data.
Separation of magnetic field lines
Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
2012-11-15
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.
Magnetic fields in spiral galaxies
NASA Astrophysics Data System (ADS)
Krause, Marita
2015-03-01
The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At ?6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).
NASA Technical Reports Server (NTRS)
Mullan, D. J.
1974-01-01
The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.
NASA Technical Reports Server (NTRS)
Mullan, D. J.
1974-01-01
The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according as the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 G. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.
Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study
NASA Technical Reports Server (NTRS)
Szabo, A.; Koval, A.; Merka, J.; Narock, T.
2011-01-01
The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the 2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions. The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed
Interplanetary Magnetic Field Power Spectrum Variations: A VHO Enabled Study
NASA Technical Reports Server (NTRS)
Szabo, A.; Koval, A.; Merka, J.; Narock, T.
2010-01-01
The newly reprocessed high time resolution (11/22 vectors/sec) Wind mission interplanetary magnetic field data and the solar wind key parameter search capability of the Virtual Heliospheric Observatory (VHO) affords an opportunity to study magnetic field power spectral density variations as a function of solar wind conditions. In the reprocessed Wind Magnetic Field Investigation (MFI) data, the spin tone and its harmonics are greatly reduced that allows the meaningful fitting of power spectra to the approx.2 Hz limit above which digitization noise becomes apparent. The power spectral density is computed and the spectral index is fitted for the MHD and ion inertial regime separately along with the break point between the two for various solar wind conditions . The time periods of fixed solar wind conditions are obtained from VHO searches that greatly simplify the process. The functional dependence of the ion inertial spectral index and break point on solar wind plasma and magnetic field conditions will be discussed
C/NOFS Magnetic Field Measurements in the Low-latitude Ionosphere during Magnetic Storms
NASA Astrophysics Data System (ADS)
Le, G.; Burke, W. J.; Pfaff, R. F.; Freudenreich, H. T.; Maus, S.; Luhr, H.
2011-12-01
The Vector Electric Field Investigation suite on the C/NOFS satellite includes a fluxgate magnetometer to monitor the Earth's magnetic fields in the low-latitude ionosphere. Measurements yield full magnetic vectors every second over the range of ± 45,000 nT with a one-bit resolution of 1.37 nT (16 bit A/D) in each component. The sensor's primary responsibility is to support calculations of both V×B and E×B with greater accuracy than can be obtained using standard magnetic field models. The data also contain information about large-scale current systems, that, when analyzed in conjunction with electric field measurements, promise to significantly expand understanding of equatorial electrodynamics. We first compare in situ measurements with the POMME (POtsdam Magnetic Model of the Earth) model to establish in-flight sensor "calibrations" and to compute magnetic residuals. At low latitudes the residuals are predominately products of the ring current during magnetic storms. Since C/NOFS provides a complete coverage of all local times every 97 minutes, magnetic field data allow studies of the temporal evolution and local-time variations of stormtime ring current. The analysis demonstrates the feasibility of using instrumented spacecraft in low-inclination orbits to extract a timely proxy for the provisional Dst index and to specify the ring current's evolution.
On the health of a vector field with RA{sup 2}/6 coupling to gravity
Karciauskas, Mindaugas; Lyth, David H., E-mail: m.karciauskas@lancaster.ac.uk, E-mail: d.lyth@lancaster.ac.uk [Department of Physics, Lancaster University, Lancaster LA1 4YB (United Kingdom)
2010-11-01
The coupling RA{sup 2}/6 of a vector field to gravity was proposed as a mechanism for generating a primordial magnetic field, and more recently as a mechanism for generating a statistically anisotropic contribution to the primordial curvature perturbation. In either case, the vector field's perturbation has both a transverse and a longitudinal component, and the latter has some unusual features which call into question the health of the theory. We publish for the first time the energy density generated by the longitudinal field perturbations, and go on to argue that the theory may well be healthy in at least some versions.
Magnetic Field Line Simulation Using a Microcomputer.
ERIC Educational Resources Information Center
Kirkup, L.
1986-01-01
Describes the implementation of a computer simulation of magnetic field lines. Discusses properties of magnetic fields and the calculation of magnetic fields at points. Provides a program listing (additional programs and teaching notes available from the author) and gives examples of several field plots. (JM)
Ballistic dynamics of Dirac particles in electro-magnetic fields
Josef Mehringer; Edgardo Stockmeyer
2014-11-21
Investigating properties of two-dimensional Dirac operators coupled to an electric and a magnetic field (perpendicular to the plane) requires in general unbounded (vector-) potentials. If the system has a certain symmetry, the fields can be described by one-dimensional potentials $V$ and $A$. Assuming that $|A|ballistically. These results are based on well-known methods in spectral dynamics together with certain new Hilbert-Schmidt bounds. We use Lorentz boosts to derive these new estimates.
Particle production of vector fields: Scale invariance is attractive
NASA Astrophysics Data System (ADS)
Wagstaff, Jacques M.; Dimopoulos, Konstantinos
2011-01-01
In a model of an Abelian vector boson with a Maxwell kinetic term and non-negative mass-squared it is demonstrated that, under fairly general conditions during inflation, a scale-invariant spectrum of perturbations for the components of a vector field, massive or not, whose kinetic function (and mass) is modulated by the inflaton field is an attractor solution. If the field is massless, or if it remains light until the end of inflation, this attractor solution also generates anisotropic stress, which can render inflation weakly anisotropic. The above two characteristics of the attractor solution can source (independently or combined together) significant statistical anisotropy in the curvature perturbation, which may well be observable in the near future.
Helical cosmological magnetic fields from extra-dimensions
NASA Astrophysics Data System (ADS)
Atmjeet, Kumar; Seshadri, T. R.; Subramanian, Kandaswamy
2015-05-01
We study the inflationary generation of helical cosmological magnetic fields in a higher-dimensional generalization of the electromagnetic theory. For this purpose, we also include a parity breaking piece to the electromagnetic action. The evolution of an extra-dimensional scale factor allows the breaking of conformal invariance of the effective electromagnetic action in 1 +3 dimensions required for such generation. Analytical solutions for the vector potential can be obtained in terms of Coulomb wave-functions for some special cases. We also present numerical solutions for the vector potential evolution in more general cases. In the presence of a higher-dimensional cosmological constant there exist solutions for the scale factors in which both normal and extra dimensional space either inflate or deflate simultaneously with the same rate. In such a scenario, with the number of extra dimensions D =4 , a scale invariant spectrum of helical magnetic field is obtained. The net helicity arises, as one helical mode comes to dominate over the other at the superhorizon scales. A magnetic field strength of the order of 10-9 G can be obtained for the inflationary scale H ?1 0-3 Mpl . Weaker fields will be generated for lower scales of inflation. Magnetic fields generated in this model respects the bounds on magnetic fields by Planck and ? -ray observations (i.e., 10-16 G
Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip, E-mail: eklim@bbso.njit.edu [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)
2012-07-01
The formation and the temporal evolution of a bipolar moving magnetic feature (MMF) was studied with high-spatial and temporal resolution. The photometric properties were observed with the New Solar Telescope at Big Bear Solar Observatory using a broadband TiO filter (705.7 nm), while the magnetic field was analyzed using the spectropolarimetric data obtained by Hinode. For the first time, we observed a bipolar MMF simultaneously in intensity images and magnetic field data, and studied the details of its structure. The vector magnetic field and the Doppler velocity of the MMF were also studied. A bipolar MMF with its positive polarity closer to the negative penumbra formed, accompanied by a bright, filamentary structure in the TiO data connecting the MMF and a dark penumbral filament. A fast downflow ({<=}2 km s{sup -1}) was detected at the positive polarity. The vector magnetic field obtained from the full Stokes inversion revealed that a bipolar MMF has a U-shaped magnetic field configuration. Our observations provide a clear intensity counterpart of the observed MMF in the photosphere, and strong evidence of the connection between the MMF and the penumbral filament as a serpentine field.
Effect of magnetic field on ball milled hard magnetic particles
NASA Astrophysics Data System (ADS)
Altuncevahir, B.; Poudyal, N.; Chakka, V. M.; Chen, K. H.; Black, T. D.; Liu, T. D.
2004-03-01
In this investigation, the powder particles of NdFeB and SmCo based alloys prepared by the ball milling in a uniform magnetic field are compared to those milled without an applied magnetic field. The ball milling was carried out for a total of 100 hours, and the powders were sampled every 25 hours. The particle size after 100 hours of milling was around 100 nm and the grain size in the particles was below 20 nm. The particles were then aligned in a magnetic field in hardening epoxy. It was found that the remanence ratios of the samples milled in an applied magnetic field were remarkably higher than those milled without field. XRD patterns also showed that the powder milled in magnetic field has better alignment than those milled without magnetic field. This technique is a novel approach to preparing anisotropic magnetic nanoparticles and has potential for producing high energy-product nanocomposite permanent magnets.
Song, Yongliang
2015-01-01
It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of SDO, earlier studies have mostly used MDI/SOHO line of sight magnetograms and assumed that magnetic fields are radial when calculating magnetic helicity injection rate from photospheric magnetograms. However, this assumption is not necessarily true. Here we use the vector magnetograms and line of sight magnetograms, both taken by HMI/SDO, to estimate the effects of non-radial magnetic field on measuring magnetic helicity injection rate. We find that: 1) The effect of non-radial magnetic field on estimating tangential velocity is relatively small; 2) On estimating magnetic helicity injection rate, the effect of non-radial magnetic field is strong when active regions are observed near the limb and is relatively small when active regions are close to disk center; 3) The effect of non-radial magnetic field becomes minor if the amount of accumulated magnetic helicity is the only conce...
The Magnetism of Meteorites and Early Solar System Magnetic Fields
NASA Astrophysics Data System (ADS)
Collinson, D. W.
1994-11-01
The characteristics of the remanent magnetization of chondrite, achondrite and shergottite, nakhlite and chassignite (SNC) meteorites are described, and interpretation in terms of magnetizing fields in the ancient Solar System discussed. The magnetism of ordinary chondrites is commonly scattered in direction within samples, implying magnetization of constituent fragments before accumulation. The magnetic history of these meteorites is uncertain because of lack of knowledge of the origin and properties of tetrataenite, an ordered FeNi alloy often carrying the bulk of the magnetization. Achondrites also often possess scattered magnetization, the primary component probably being acquired during cooling after differentiation of the parent body. A magnetizing field of internal origin is possible. Estimates of magnetizing field strength are in the approximate range 5-100 ? T, with carbonaceous chondrites showing the highest values. The SNC meteorites, probably originating on Mars, provide evidence for a weak, ancient Martian magnetic field of the order 1 ? T.
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2
Fornberg, Bengt
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy
Lyapunov Vector Fields for Autonomous UAV Flight Control1 Dale A. Lawrence2
Frew, Eric W.
, 80309 Abstract General techniques for constructing vector fields for UAV guidance are provided. Nomenclature r = UAV position vector relative to an inertial reference frame ( )z,y,x = Inertial frame plane )r( = Vector field normalizer = Relative circulation vs. contraction weighting factor = Vector
J. P. Silva; A. J. Silvestre
2005-01-01
We compare the magnetic field at the centre and the self-magnetic flux through a current-carrying circular loop, with those obtained for current-carrying polygons with the same perimeter. As the magnetic field diverges at the position of the wires, we compare the self-fluxes utilizing several regularization procedures. The calculation is best performed utilizing the vector potential, thus highlighting its usefulness in
Two-dimensional magnetic properties of silicon steel sheet subjected to a rotating field
Masato Enokizono; Takashi Todaka; Shinichi Kanao; Johannes Sievert
1993-01-01
A study of the two-dimensional rotational magnetic properties of a steel sheet are discussed. These are measured making use of the vector relation between magnetic field strength H and magnetic flux density B. The results of this study lead to the following main conclusions: the permeability tensor becomes a full matrix under rotating flux; the off-diagonal terms of the permeability
Magnetic properties prediction of NdFeB magnets by using support vector regression
NASA Astrophysics Data System (ADS)
Cheng, Wende
2014-09-01
A novel model using support vector regression (SVR) combined with particle swarm optimization (PSO) was employed to construct mathematical model for prediction of the magnetic properties of the NdFeB magnets. The leave-one-out cross-validation (LOOCV) test results strongly supports that the generalization ability of SVR is high enough. Predicted results show that the mean absolute percentage error for magnetic remanence Br, coercivity Hcj and maximum magnetic energy product (BH)max are 0.53%, 3.90%, 1.73%, and the correlation coefficient (R2) is as high as 0.839, 0.967 and 0.940, respectively. This investigation suggests that the PSO-SVR is not only an effective and practical method to simulate the properties of NdFeB, but also a powerful tool to optimatize designing or controlling the experimental process.
NASA Astrophysics Data System (ADS)
Vlaskou, Dialechti; Pradhan, Pallab; Bergemann, Christian; Klibanov, Alexander L.; Hensel, Karin; Schmitz, Georg; Plank, Christian; Mykhaylyk, Olga
2010-12-01
Based on the concept of magnetofection, we prepared lipid shell microbubbles loaded with highly positively charged iron oxide magnetic nanoparticles through electrostatic and matrix affinity interactions. These magnetic microbubbles showed strong ultrasound contrast. When the magnetic microbubbles were mixed with plasmid DNA encoding a reporter gene, gene delivery to HeLa cells was achieved only when ultrasound was applied. Gene transfer efficiency strongly depended on the application of a gradient magnetic field. Treatment of HeLa cells with the microbubbles and ultrasound resulted in strong concentration-dependent cytotoxic effects, whereas ultrasound alone, lipid microbubbles alone, magnetic nanoparticles or magnetic microbubbles alone did not significantly affect cell viability. These magnetic microbubbles could be used as magnetically targeted diagnostic agents for real-time ultrasound imaging or for cancer therapy, therapy of vascular thrombosis and gene therapy.
Explaining Mercury's peculiar magnetic field
NASA Astrophysics Data System (ADS)
Wicht, Johannes; Cao, Hao; Heyner, Daniel; Dietrich, Wieland; Christensen, Ulrich R.
2014-05-01
MESSENGER magnetometer data revealed that Mercury's magnetic field is not only particularly weak but also has a peculiar geometry. The MESSENGER team finds that the location of the magnetic equator always lies significantly north of the geographic equator, is largely independent of the distance to the planet, and also varies only weakly with longitude. The field is best described by an axial dipole that is offset to the north by about 20% of the planetary radius. In terms of classical Gauss coefficients, this translates into a low axial dipole component of g10= -190 nT but a relatively large axial quadrupole contribution that amounts to roughly 40% of this value. The axial octupole is also sizable while higher harmonic contributions are much weaker. Very remarkable is also the fact that the equatorial dipole contribution is very small, consistent with a dipole tilt below 0.8 degree, and this is also true for the other non-axisymmetic field contributions. We analyze several numerical dynamos concerning their capability of explaining Mercury's magnetic field. Classical schemes geared to model the geomagnetic field typically show a much weaker quadrupole component and thus a smaller offset. The onset only becomes larger when the dynamo operates in the multipolar regime at higher Rayleigh numbers. However, since the more complex dynamics generally promotes all higher multipole contributions the location of the magnetic equator varies strongly with longitude and distance to the planet. The situation improves when introducing a stably stratified outer layer in the dynamo region, representing either a rigid FeS layer or a sub-adiabatic core-mantle boundary heat flux. This layer filters out the higher harmonic contributions and the field not only becomes sufficiently weak but also assumes a Mercury like offset geometry during a few percent of the simulation time. To increase the likelihood for the offset configuration, the north-south symmetry must be permanently broken and we explore two scenarios. Increasing the heat flux through the northern hemisphere of the core-mantle boundary is an obvious choice but is not supported by current models for Mercury's mantle. We find that a combination of internal rather than bottom driving and an increased heat flux through the equatorial region of the core-mantle boundary also promotes the required symmetry breaking and results in very Mercury like fields. The reason is that the imposed heat flux pattern, though being equatorially symmetric, lowers the critical Rayleigh number for the onset of equatorially anti-symmetric convection modes. In both scenarios, a stably stratified layer or a feedback coupling to the magnetospheric field is required for lowering the field strength to Mercury-like values.
Anisotropic Magnetism in Field-Structured Composites
Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene
1999-06-24
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.
Variability in Martian Magnetic Field Topology
NASA Astrophysics Data System (ADS)
Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.
2014-07-01
We have determined the locations of open and closed magnetic field lines at Mars as a function of four different controlling influences: solar wind magnetic field direction, solar wind pressure, martian season, and solar EUV flux.
Passive Magnetic Shielding in Gradient Fields
Bidinosti, C P
2013-01-01
The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...
Plasma stability in a dipole magnetic field
Simakov, Andrei N., 1974-
2001-01-01
The MHD and kinetic stability of an axially symmetric plasma, confined by a poloidal magnetic field with closed lines, is considered. In such a system the stabilizing effects of plasma compression and magnetic field ...
Low-frequency fluctuations in plasma magnetic fields
Cable, S.; Tajima, T. (Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712 (United States))
1992-09-15
It is shown that even a nonmagnetized plasma with temperature {ital T} sustains zero-frequency magnetic fluctuations in thermal equilibrium. Fluctuations in electric and magnetic fields, as well as in densities, are computed. Four cases are studied: a cold, gaseous, isotropic, nonmagnetized plasma; a cold, gaseous plasma in a uniform magnetic field; a warm, gaseous plasma described by kinetic theory; and a degenerate electron plasma. For the simple gaseous plasma, the fluctuation strength of the magnetic field as a function of frequency and wave number is calculated with the aid of the fluctuation-dissipation theorem. This calculation is done for both collisional and collisionless plasmas. The magnetic-field fluctuation spectrum of each plasma has a large zero-frequency peak. The peak is a Dirac {delta} function in the collisionless plasma; it is broadened into a Lorentzian curve in the collisional plasma. The plasma causes a low-frequency cutoff in the typical blackbody radiation spectrum, and the energy under the discovered peak approximates the energy lost in this cutoff. When the imposed magnetic field is weak, the magnetic-field wave-vector fluctuation spectra of the two lowest modes are independent of the strength of the imposed field. Further, these modes contain finite energy even when the imposed field is zero. It is the energy of these modes that forms the zero-frequency peak of the nonmagnetized plasma. In deriving these results, a simple relationship between the dispersion relation and the fluctuation power spectrum of electromagnetic waves is found. The warm plasma is shown, by kinetic theory, to exhibit a zero-frequency peak in its magnetic-field fluctuation spectrum as well. For the degenerate plasma, we find that electric-field fluctuations and number-density fluctuations vanish at zero frequency; however, the magnetic-field power spectrum diverges at zero frequency.
Aharonov--Bohm E#ect in Scattering by a Chain of Point--like Magnetic Fields
Aharonov--Bohm E#ect in Scattering by a Chain of Point--like Magnetic Fields Hiroshi T. Ito the scattering by several point--like magnetic fields at large separation in two dimensions. We derive. Even if a magnetic field is compactly supported, the corresponding vector potential does
Development of Techniques for Visualization of Scalar and Vector Fields in the Immersive Environment
NASA Technical Reports Server (NTRS)
Bidasaria, Hari B.; Wilson, John W.; Nealy, John E.
2005-01-01
Visualization of scalar and vector fields in the immersive environment (CAVE - Cave Automated Virtual Environment) is important for its application to radiation shielding research at NASA Langley Research Center. A complete methodology and the underlying software for this purpose have been developed. The developed software has been put to use for the visualization of the earth s magnetic field, and in particular for the study of the South Atlantic Anomaly. The methodology has also been put to use for the visualization of geomagnetically trapped protons and electrons within Earth's magnetosphere.
Minimal Distortion Morphs Generated by Time-Dependent Vector Fields
Bihun, Oksana; Harris, Steven G
2008-01-01
A morph between two Riemannian $n$-manifolds is an isotopy between them together with the set of all intermediate manifolds equipped with Riemannian metrics. We propose measures of the distortion produced by some classes of morphs and diffeomorphisms between two isotopic Riemannian $n$-manifolds and, with respect to these classes, prove the existence of minimal distortion morphs and diffeomorphisms. In particular, we consider the class of time-dependent vector fields (on an open subset $\\Omega$ of $ \\R^{n+1}$ in which the manifolds are embedded) that generate morphs between two manifolds $M$ and $N$ via an evolution equation, define the bending and the morphing distortion energies for these morphs, and prove the existence of minimizers of the corresponding functionals in the set of time-dependent vector fields that generate morphs between $M$ and $N$ and are $L^2$ functions from $[0,1]$ to the Sobolev space $W^{k,2}_0(\\Omega,\\R^{n+1})$.
New techniques in 3D scalar and vector field visualization
Max, N.; Crawfis, R.; Becker, B.
1993-05-05
At Lawrence Livermore National Laboratory (LLNL) we have recently developed several techniques for volume visualization of scalar and vector fields, all of which use back-to-front compositing. The first renders volume density clouds by compositing polyhedral volume cells or their faces. The second is a ``splatting`` scheme which composites textures used to reconstruct the scalar or vector fields. One version calculates the necessary texture values in software, and another takes advantage of hardware texture mapping. The next technique renders contour surface polygons using semi-transparent textures, which adjust appropriately when the surfaces deform in a flow, or change topology. The final one renders the ``flow volume`` of smoke or dye tracer swept out by a fluid flowing through a small generating polygon. All of these techniques are applied to a climate model data set, to visualize cloud density and wind velocity.
Near-field magnetic communication
R. Bansal
2004-01-01
Even as cell phones have shrunk in size while boasting an ever-increasing array of features, two things about them haven't changed much: they still sprout a stubby antenna and, if you want a headset, you have to put up with an unwieldy wire connecting the headset and the phone. Thanks to a patented technology called near-field magnetic communication (NFMC), from
Rotating copper plasmoid in external magnetic field
Pandey, Pramod K.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Uttar Pradesh 208 016 (India)
2013-02-15
Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.
Magnetic field effect for cellulose nanofiber alignment
NASA Astrophysics Data System (ADS)
Kim, Jaehwan; Chen, Yi; Kang, Kwang-Sun; Park, Young-Bin; Schwartz, Mark
2008-11-01
Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.
Extraterrestrial magnetic fields - Achievements and opportunities
E. J. Smith; C. P. Sonett
1976-01-01
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: magnetometers and how they operate, problems arising from spacecraft-generated magnetic fields and appropriate countermeasures and on-board processing of magnetometer data. The solar wind and interplanetary magnetic field, the
On completeness of orbits of Killing vector fields
Piotr T. Chrusciel
1993-04-21
A Theorem is proved which reduces the problem of completeness of orbits of Killing vector fields in maximal globally hyperbolic, say vacuum, space--times to some properties of the orbits near the Cauchy surface. In particular it is shown that all Killing orbits are complete in maximal developements of asymptotically flat Cauchy data, or of Cauchy data prescribed on a compact manifold. This result gives a significant strengthening of the uniqueness theorems for black holes.
Pulsed-Field Gradient Nuclear Magnetic
Duncan, James S.
Pulsed-Field Gradient Nuclear Magnetic Resonance as a Tool for Studying Translational Diffusion and biochemical systems. Pulsed-field gradient nuclear magnetic resonance pro- vides a convenient and noninvasive spin-echo pulse sequence contain- ing a magnetic field gradient pulse in each period is used to measure
Primordial magnetic field limits from cosmological data
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
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.
Rays and foci in a magneto-ionic medium with linearly varying magnetic field
R. White; M. J. Laird
1980-01-01
An analytical study is carried out of rays from a source in a magneto-ionic medium in which the magnetic field is linear in the position coordinates. A general solution is given, and special cases, including that in which the magnetic field vector is confined to a plane, are examined. In the latter case, the specific sub-case of null current density,
Some Characteristics of the Upper-Air Magnetic Field and Ionospheric Currents
Alfred J. Zmuda
1960-01-01
Characteristics of the upper-air magnetic field and ionospheric currents are determined through an analysis of published rocket data on the magnetic scalar intensity. For the region between the earth's surface and the E layer of the ionosphere, the observed values are compared with values obtained by extrapolating the surface vector field. The agreement between the two sets of values is
A new current dipole model satisfying current continuity for inverse magnetic field source problems
Hisashi Endo; Toshiyuki Takagi; Yoshifuru Saito
2005-01-01
A new current dipole model is proposed to estimate magnetic field sources. A set of the current dipoles represents a closed-loop current element, always satisfying current continuity. The target region is filled with the closed-loop current elements to derive a system of equations, then its solution estimates unknown current distribution from given magnetic field data. The generalized vector sampled pattern
Measuring the magnetic fields of jupiter and the outer solar system
E. Smith; B. Connor
1975-01-01
The vector helium magnetometer, one of the Pioneer-Jupiter experiments, has measured the magnetic field of Jupiter and the interplanetary magnetic field in the outer solar system. The comprehensive scientific objectives of the investigations are explained and are then translated into the major instrument requirements. The principles of operation of the magnetometer, which involve the optical pumping of metastable helium, are
C. Carr; P. Brown; T. L. Zhang; J. Gloag; T. Horbury; E. Lucek; W. Magnes; H. O'Brien; T. Oddy; U. Auster; P. Austin; O. Aydogar; A. Balogh; W. Baumjohann; T. Beek; H. Eichelberger; K.-H. Fornacon; E. Georgescu; K.-H. Glassmeier; M. Ludlam; R. Nakamura; I. Richter
2005-01-01
One of the primary objectives of the Double Star mission is the accurate measurement of the magnetic field vector along the orbits of the two spacecraft. The magnetic field is an essential parameter for the understanding of space plasma processes and is also required for the effective interpretation of data from the other instruments on the spacecraft. We present the
Magnetic monopole and the nature of the static magnetic field
Xiuqing Huang
2008-12-10
We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.
Cluster Magnetic Fields from Galactic Outflows
J. Donnert; K. Dolag; H. Lesch; E. Müller
2008-10-24
We performed cosmological, magneto-hydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields are galactic outflows during the star-burst phase of galactic evolution. To do this we coupled a semi-analytical model for magnetized galactic winds as suggested by \\citet{2006MNRAS.370..319B} to our cosmological simulation. We find that the strength and structure of magnetic fields observed in galaxy clusters are well reproduced for a wide range of model parameters for the magnetized, galactic winds and do only weakly depend on the exact magnetic structure within the assumed galactic outflows. Although the evolution of a primordial magnetic seed field shows no significant differences to that of galaxy clusters fields from previous studies, we find that the magnetic field pollution in the diffuse medium within filaments is below the level predicted by scenarios with pure primordial magnetic seed field. We therefore conclude that magnetized galactic outflows and their subsequent evolution within the intra-cluster medium can fully account for the observed magnetic fields in galaxy clusters. Our findings also suggest that measuring cosmological magnetic fields in low-density environments such as filaments is much more useful than observing cluster magnetic fields to infer their possible origin.
Bats respond to very weak magnetic fields.
Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang
2015-01-01
How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae) can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 ?T; the lowest field strength tested here), the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 ?T), despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05). Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years. PMID:25922944
On Killing vector fields of a homogeneous and isotropic universe in closed model
Ruslan Sharipov
2007-08-19
Killing vector fields of a closed homogeneous and isotropic universe are studied. It is shown that in general case there is no time-like Killing vector fields in such a universe. Two exceptional cases are revealed.
Petrie, G. J. D. [National Solar Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
2012-11-01
We analyze the spatial and temporal variations of the abrupt photospheric magnetic changes associated with six major flares using 12 minute, 0.''5 pixel{sup -1} vector magnetograms from NASA's Helioseismic and Magnetic Imager instrument on the Solar Dynamics Observatory satellite. The six major flares occurred near the main magnetic neutral lines of four active regions, NOAA 11158, 11166, 11283, and 11429. During all six flares the neutral-line field vectors became stronger and more horizontal, in each case almost entirely due to strengthening of the horizontal field components parallel to the neutral line. In all six cases the neutral-line pre-flare fields were more vertical than the reference potential fields, and collapsed abruptly and permanently closer to potential-field tilt angles during every flare, implying that the relaxation of magnetic stress associated with non-potential tilt angles plays a major role during major flares. The shear angle with respect to the reference potential field did not show such a pattern, demonstrating that flare processes do not generally relieve magnetic stresses associated with photospheric magnetic shear. The horizontal fields became significantly and permanently more aligned with the neutral line during the four largest flares, suggesting that the collapsing field is on average more aligned with the neutral line than the pre-flare neutral-line field. The vertical Lorentz force had a large, abrupt, permanent downward change during each of the flares, consistent with loop collapse. The horizontal Lorentz force changes acted mostly parallel to the neutral line in opposite directions on each side, a signature of the fields contracting during the flare, pulling the two sides of the neutral line toward each other. The greater effect of the flares on field tilt than on shear may be explained by photospheric line-tying.
Suppression of magnetic relaxation by a transverse alternating magnetic field
Voloshin, I. F.; Kalinov, A. V.; Fisher, L. M. [All-Russia Electrical Engineering Institute (Russian Federation)], E-mail: fisher@vei.ru; Yampol'skii, V. A. [National Academy of Sciences of Ukraine, Institute of Radiophysics and Electronics (Ukraine)], E-mail: yam@vk.kharkov.ua
2007-07-15
The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.
Magnetic field sources and their threat to magnetic media
NASA Technical Reports Server (NTRS)
Jewell, Steve
1993-01-01
Magnetic storage media (tapes, disks, cards, etc.) may be damaged by external magnetic fields. The potential for such damage has been researched, but no objective standard exists for the protection of such media. This paper summarizes a magnetic storage facility standard, Publication 933, that ensures magnetic protection of data storage media.
Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field
Mauel, M; Ryutov, D; Kesner, J
2003-12-02
In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.
Mars Global Surveyor Observations of Solar Wind Magnetic Field Draping Around Mars
Dana H. Crider; David A. Brain; Mario H. Acuña; Didier Vignes; Christian Mazelle; Cesar Bertucci
2004-01-01
We examine the magnetic field in the martian magnetosheath due to solar wind draping. Mars Global Surveyor provided 3-D vector\\u000a magnetic field measurements at a large range of altitudes, local times, and solar zenith angles as the spacecraft orbit evolved.\\u000a We choose orbits with very clean signatures of draping to establish the nominal morphology of the magnetic field lines at
Conversion of magnetic field energy into kinetic energy in the solar wind
NASA Technical Reports Server (NTRS)
Whang, Y. C.
1972-01-01
The outflow of the solar magnetic field energy (the radial component of the Poynting vector) per steradian is inversely proportional to the solar wind velocity. It is a decreasing function of the heliocentric distance. When the magnetic field effect is included in the one-fluid model of the solar wind, the transformation of magnetic field energy into kinetic energy during the expansion process increases the solar wind velocity at 1 AU by 17 percent.
Compact low field magnetic resonance imaging magnet: Design and optimization
M. Sciandrone; G. Placidi; L. Testa; A. Sotgiu
2000-01-01
Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter.
Shull, Kenneth R.
Magnetic Fields1 Increasingly, instruments that generate large static magnetic fields (e.g., NMR spectrometers, MRI) are present in research laboratories. Such magnets typically have fields of 14,000 to 235,000 G (1.4 to 23.5 T), far above that of Earth's magnetic field, which is approximately 0.5 G
Magnetic field perturbations in the systems where only poloidal magnetic field is present*
1 Magnetic field perturbations in the systems where only poloidal magnetic field is present* D In some plasma confinement systems the confinement is provided by a poloidal magnetic field (no toroidal magnetic field is present). Examples include FRC, levitated dipoles, and long diffuse pinches. We consider
Coexistence of Multiple Phases in Magnetized Quark Matter with Vector Repulsion
Denke, Robson Z
2015-01-01
We explore the phase structure of dense magnetized quark matter when a repulsive vector interaction, parametrized by $G_V$, is present. Our results show that for a given magnetic field intensity ($B$) one may find a value of $G_V$ for which quark matter may coexist at three different baryonic density values leading to the appearance of two triple points in the phase diagram which have not been observed before. Another novel result is that at high pressure and low temperature we observe a first order transition which presents a negative slope in the $P-T$ that is reminiscent of the solid-liquid transition line observed within the water phase diagram. These unusual patterns occur for $G_V$ and $B$ values which lie within the range presently considered in many investigations related to the study of magnetars.
Coexistence of Multiple Phases in Magnetized Quark Matter with Vector Repulsion
Robson Z. Denke; Marcus Benghi Pinto
2015-06-17
We explore the phase structure of dense magnetized quark matter when a repulsive vector interaction, parametrized by $G_V$, is present. Our results show that for a given magnetic field intensity ($B$) one may find a value of $G_V$ for which quark matter may coexist at three different baryonic density values leading to the appearance of two triple points in the phase diagram which have not been observed before. Another novel result is that at high pressure and low temperature we observe a first order transition which presents a negative slope in the $P-T$ that is reminiscent of the solid-liquid transition line observed within the water phase diagram. These unusual patterns occur for $G_V$ and $B$ values which lie within the range presently considered in many investigations related to the study of magnetars.
How to Draw Magnetic Fields - II
NSDL National Science Digital Library
This is an activity about depicting magnetic polarity. Learners will observe several provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines and depict the polarities for several orientations, including an arrangement of six magnetic poles. This is the fourth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.
The Local Stellar Velocity Field via Vector Spherical Harmonics
NASA Technical Reports Server (NTRS)
Makarov, V. V.; Murphy, D. W.
2007-01-01
We analyze the local field of stellar tangential velocities for a sample of 42,339 nonbinary Hipparcos stars with accurate parallaxes, using a vector spherical harmonic formalism.We derive simple relations between the parameters of the classical linear model (Ogorodnikov-Milne) of the local systemic field and low-degree terms of the general vector harmonic decomposition. Taking advantage of these relationships, we determine the solar velocity with respect to the local stars of (V(sub X), V(sub Y), V(sub Z)) = (10.5, 18.5, 7.3) +/- 0.1 km s(exp -1) not for the asymmetric drift with respect to the local standard of rest. If only stars more distant than 100 pc are considered, the peculiar solar motion is (V(sub X), V(sub Y), V(sub Z)) = (9.9, 15.6, 6.9) +/- 0.2 km s(exp -1). The adverse effects of harmonic leakage, which occurs between the reflex solar motion represented by the three electric vector harmonics in the velocity space and higher degree harmonics in the proper-motion space, are eliminated in our analysis by direct subtraction of the reflex solar velocity in its tangential components for each star...
Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization
Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)
2000-12-19
In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.
Magnetic field driven domain-wall propagation in magnetic nanowires
Wang, X.R. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China); Yan, P. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)], E-mail: yanpeng@ust.hk; Lu, J.; He, C. [Physics Department, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)
2009-08-15
The mechanism of magnetic field induced magnetic domain-wall (DW) propagation in a nanowire is revealed: A static DW cannot exist in a homogeneous magnetic nanowire when an external magnetic field is applied. Thus, a DW must vary with time under a static magnetic field. A moving DW must dissipate energy due to the Gilbert damping. As a result, the wire has to release its Zeeman energy through the DW propagation along the field direction. The DW propagation speed is proportional to the energy dissipation rate that is determined by the DW structure. The negative differential mobility in the intermediate field is due to the transition from high energy dissipation at low field to low energy dissipation at high field. For the field larger than the so-called Walker breakdown field, DW plane precesses around the wire, leading to the propagation speed oscillation.
Adaptive modular vector field control for robot contact tasks in uncertain environment
Yohei Saitoh; Zhiwei Luo; K. Watanabe
2003-01-01
This paper proposes an adaptive modular vector field control (AMVFC) approach for a robot manipulator to interact with its uncertain environmental geometric constraints. Started from the uncertain geometric model of the environment, the approach first parameterizes the desired velocity vector field of the robot by the weighted combination of a set of basis vector fields. Then, to overcome the influences
THE ZERO SET OF CONFORMAL VECTOR FIELDS ANDREI MOROIANU AND LIVIU ORNEA
Paris-Sud XI, Université de
THE ZERO SET OF CONFORMAL VECTOR FIELDS ANDREI MOROIANU AND LIVIU ORNEA Abstract. We show that every connected component of the zero set of a conformal vector field on a Riemannian manifold. Kobayashi, [3], states that the connected components of the set of zeros of a Killing vector field
Report of the panel on geopotential fields: Magnetic field, section 9
NASA Technical Reports Server (NTRS)
Achache, Jose J.; Backus, George E.; Benton, Edward R.; Harrison, Christopher G. A.; Langel, Robert A.
1991-01-01
The objective of the NASA Geodynamics program for magnetic field measurements is to study the physical state, processes and evolution of the Earth and its environment via interpretation of measurements of the near Earth magnetic field in conjunction with other geophysical data. The fields measured derive from sources in the core, the lithosphere, the ionosphere, and the magnetosphere. Panel recommendations include initiation of multi-decade long continuous scalar and vector measurements of the Earth's magnetic field by launching a five year satellite mission to measure the field to about 1 nT accuracy, improvement of our resolution of the lithographic component of the field by developing a low altitude satellite mission, and support of theoretical studies and continuing analysis of data to better understand the source physics and improve the modeling capabilities for different source regions.
Magnetic Helicity of the Parker Interplanetary Magnetic Field and Alfvén Simple Waves
NASA Astrophysics Data System (ADS)
Webb, G. M.; Hu, Q.; Dasgupta, B.; Zank, G. P.; Roberts, D. A.
2011-09-01
We discuss the relative magnetic helicity of (a) the Parker [1] interplanetary spiral magnetic field, and (b) multi-dimensional simple Alfvén waves in the solar wind. We discuss the different forms of the magnetic vector potential A using either (a) the Coulomb gauge associated with solving a Poisson equation for A, in which the current acts as a source, (b) by using the homotopy form of A or (c) using a poloidal-toroidal decomposition of the magnetic field B. For the Parker field, we show that the relative helicity for a hemispherical volume north of the current sheet is negative, and the relative helicity for a similar volume south of the current sheet is positive. The relative helicity is also calculated in terms of the linkage of the poloidal and toroidal magnetic flux. These results extend the results of Bieber et al. [2] on the magnetic helicity of the Parker field, and are related to the helicity injection rate into the solar wind determined by Berger and Ruzmaikin [3]. Similar methods are used to determine the magnetic helicity for fully nonlinear Alfvén waves in the solar wind for which the magnetic field B has a constant magnitude, and the hodograph of B moves on a sphere. The solutions have |B| = const. hodographs, similar to nonlinear Alfvén waves observed in the solar wind by Bruno et al. [4], Roberts and Goldstein [5] and Gosling et al. [6]. Both shear and 2D torsional Alfvén waves are investigated.
Modelling of solar magnetic field and prominence structures
NASA Technical Reports Server (NTRS)
Wu, Shi Tsan
1988-01-01
Using plasma theory, the interaction is studied between high frequency and magnetohydrodynamic (MHD) waves from which a set of coupling equations resulted. On the basis of this formalism, the modulation instabilities of an electromagnetic soliton in a current sheet are examined, and it is shown that there is a resistive instability at the onset of the magnetic field reconnection. This mechanism could be used to explain the onset of solar flares and prominences. To improve the resolution of vector magnetic fields at the sun's surface, state-of-the-art optics is examined to improve the design and fabrication of a new spaceborne solar vector magnetograph as part of the SAMEX (Solar Active Measurements Experiment) program.
Mapping of the lithospheric magnetic field using CHAMP satellite data
NASA Astrophysics Data System (ADS)
Saich, B.; Hamoudi, M.; Berguig, M. C.
2013-09-01
In this work, we will present a mapping of the magnetic field generated by the heterogeneities of magnetization of the lithospheric rocks. This field is so called the lithospheric field and it is the result of two contributions: the induced contribution and the remanent magnetization contribution. It therefore brings a crucial constraint on the magnetic properties of the crustal rocks. To map this field, we will use the scalar and vector data collected during CHAMP mission from July 15th, 2000 to September 19th, 2010. The sampling frequencies of 1 Hz at the average altitude of about 350 km of measurements allow us to obtain a high resolution mapping. The method used to reduce the effect of the other contributions of the Earth magnetic field is based on the separation of the internal field using models of 16th degrees. These models were calculated for each of three months in order to move secular variations. The use of these algorithms has permitted to map the strong lithospheric magnetic anomalies of large wavelength using only raw satellite observations.
Killing Vector Fields in Three Dimensions: A Method to Solve Massive Gravity Field Equations
Metin Gurses
2010-07-29
Killing vector fields in three dimensions play important role in the construction of the related spacetime geometry. In this work we show that when a three dimensional geometry admits a Killing vector field then the Ricci tensor of the geometry is determined in terms of the Killing vector field and its scalars. In this way we can generate all products and covariant derivatives at any order of the ricci tensor. Using this property we give ways of solving the field equations of Topologically Massive Gravity (TMG) and New Massive Gravity (NMG) introduced recently. In particular when the scalars of the Killing vector field (timelike, spacelike and null cases) are constants then all three dimensional symmetric tensors of the geometry, the ricci and einstein tensors, their covariant derivatives at all orders, their products of all orders are completely determined by the Killing vector field and the metric. Hence the corresponding three dimensional metrics are strong candidates of solving all higher derivative gravitational field equations in three dimensions.
Magnetic field calculation and measurement of active magnetic bearings
NASA Astrophysics Data System (ADS)
Ding, Guoping; Zhou, Zude; Hu, Yefa
2006-11-01
Magnetic Bearings are typical devices in which electric energy and mechanical energy convert mutually. Magnetic Field indicates the relationship between 2 of the most important parameters in a magnetic bearing - current and force. This paper presents calculation and measurement of the magnetic field distribution of a self-designed magnetic bearing. Firstly, the static Maxwell's equations of the magnetic bearing are presented and a Finite Element Analysis (FEA) is found to solve the equations and get post-process results by means of ANSYS software. Secondly, to confirm the calculation results a Lakeshore460 3-channel Gaussmeter is used to measure the magnetic flux density of the magnetic bearing in X, Y, Z directions accurately. According to the measurement data the author constructs a 3D magnetic field distribution digital model by means of MATLAB software. Thirdly, the calculation results and the measurement data are compared and analyzed; the comparing result indicates that the calculation results are consistent with the measurement data in allowable dimension variation, which means that the FEA calculation method of the magnetic bearing has high precision. Finally, it is concluded that the magnetic field calculation and measurement can accurately reflect the real magnetic distribution in the magnetic bearing and the result can guide the design and analysis of the magnetic bearing effectively.
Full 180° Magnetization Reversal with Electric Fields
Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.
2014-01-01
Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070
Full 180° magnetization reversal with electric fields.
Wang, J J; Hu, J M; Ma, J; Zhang, J X; Chen, L Q; Nan, C W
2014-01-01
Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070
Full 180° Magnetization Reversal with Electric Fields
NASA Astrophysics Data System (ADS)
Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.
2014-12-01
Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals.
Vlasov Equation In Magnetic Field
Biao Wu
1999-09-07
The linearized Vlasov equation for a plasma system in a uniform magnetic field and the corresponding linear Vlasov operator are studied. The spectrum and the corresponding eigenfunctions of the Vlasov operator are found. The spectrum of this operator consists of two parts: one is continuous and real; the other is discrete and complex. Interestingly, the real eigenvalues are infinitely degenerate, which causes difficulty solving this initial value problem by using the conventional eigenfunction expansion method. Finally, the Vlasov equation is solved by the resolvent method.
Boundary-integral method for poloidal axisymmetric AC magnetic fields
Janis Priede; Gunter Gerbeth
2006-01-01
This paper presents a boundary-integral equation (BIE) method for the\\u000acalculation of poloidal axisymmetric magnetic fields applicable in a wide range\\u000aof ac frequencies. The method is based on the vector potential formulation and\\u000ait uses the Green's functions of Laplace and Helmholtz equations for the\\u000aexterior and interior of conductors, respectively. The work is particularly\\u000afocused on a calculation
Deformation of Water by a Magnetic Field
ERIC Educational Resources Information Center
Chen, Zijun; Dahlberg, E. Dan
2011-01-01
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…
Coupled Field Synthesis in Magnetic Fluid Hyperthermia
Paolo Di Barba; Fabrizio Dughiero; Elisabetta Sieni; Alessandro Candeo
2011-01-01
AGNETIC fluid hyperthermia (MFH) uses magnetic nanoparticles (NPs) excited by an ac magnetic field to destroy cancer tissues (i.e., the target tissue) by means of induced heat [1]. In general, this kind of device exhibits a large iron core. For instance, at the Charité hospital in Berlin, Germany, the equipment for this kind of technique has a magnetic field source
Field Corrections of Open MRI Superconducting Magnets
Tetsuya Matsuda; Akihiko Ariyoshi; Hajime Tanabe
2005-01-01
We constructed open MRI superconducting magnets with an iron yoke that generates a 0.7T highly uniform magnetic field. A program that compensates for the error field of those magnets was developed that uses linear programming to achieve an optimal arrangement of a large number of small iron shims. Since additional homogeneity compensation near the target value becomes difficult, we also
Neutrinos with Mixing in Twisting Magnetic Fields
E. Kh. Akhmedov; S. T. Petcov; A. Yu. Smirnov
1993-01-06
Transitions in a system of neutrinos with vacuum mixing and magnetic moments, propagating in matter and transverse magnetic field, are considered. It is shown that in the realistic case of magnetic field direction varying along the neutrino path qualitatively new phenomena become possible: permutation of neutrino conversion resonances, appearance of resonances in the neutrino-antineutrino ($\
ELECTRON SPECTROMETER WITH TOROIDAL MAGNETIC FIELD
A. E. Dubinov; N. V. Minashkin; V. D. Selemir; N. V. Stepanov; V. E. Vatrunin
1993-01-01
The spectrometer allows to measure the spectrum of the electron beam, generated in the magnetized diode. Principle of the spectrometer's operation consists in spatial separation of Merent energies particles in gradient static magnetic field. Numerical integration of electron movement equations in the toroidal magnetic field %l\\/r -manner, is consistent with the experimental results received at 1-3000 accelerator. The results of
Activity recognition using a mixture of vector fields.
Nascimento, Jacinto C; Figueiredo, Mário A T; Marques, Jorge S
2013-05-01
The analysis of moving objects in image sequences (video) has been one of the major themes in computer vision. In this paper, we focus on video-surveillance tasks; more specifically, we consider pedestrian trajectories and propose modeling them through a small set of motion/vector fields together with a space-varying switching mechanism. Despite the diversity of motion patterns that can occur in a given scene, we show that it is often possible to find a relatively small number of typical behaviors, and model each of these behaviors by a "simple" motion field. We increase the expressiveness of the formulation by allowing the trajectories to switch from one motion field to another, in a space-dependent manner. We present an expectation-maximization algorithm to learn all the parameters of the model, and apply it to trajectory classification tasks. Experiments with both synthetic and real data support the claims about the performance of the proposed approach. PMID:23193235
Exploring Vector Fields with Distribution-based Streamline Analysis
Lu, Kewei; Chaudhuri, Abon; Lee, Teng-Yok; Shen, Han-Wei; Wong, Pak C.
2013-02-26
Streamline-based techniques are designed based on the idea that properties of streamlines are indicative of features in the underlying field. In this paper, we show that statistical distributions of measurements along the trajectory of a streamline can be used as a robust and effective descriptor to measure the similarity between streamlines. With the distribution-based approach, we present a framework for interactive exploration of 3D vector fields with streamline query and clustering. Streamline queries allow us to rapidly identify streamlines that share similar geometric features to the target streamline. Streamline clustering allows us to group together streamlines of similar shapes. Based on users selection, different clusters with different features at different levels of detail can be visualized to highlight features in 3D flow fields. We demonstrate the utility of our framework with simulation data sets of varying nature and size.
Use of along-track magnetic field differences in lithospheric field modelling
NASA Astrophysics Data System (ADS)
Kotsiaros, S.; Finlay, C. C.; Olsen, N.
2015-02-01
We demonstrate that first differences of polar orbiting satellite magnetic data in the along-track direction can be used to obtain high resolution models of the lithospheric field. Along-track differences approximate the north-south magnetic field gradients for non-polar latitudes. In a test case, using 2 yr of low altitude data from the CHAMP satellite, we show that use of along-track differences of vector field data results in an enhanced recovery of the small scale lithospheric field, compared to the use of the vector field data themselves. We show that the along-track technique performs especially well in the estimation of near zonal spherical harmonic coefficients. Moreover, lithospheric field models determined using along-track differences are found to be less sensitive to the presence of unmodelled external field contributions and problems associated with the polar gap are ameliorated. Experiments in modelling the Earth's lithospheric magnetic field with along-track differences are presented here as a proof of concept. We anticipate that use of such along-track differences in combination with east-west field differences, as are now provided by the Swarm satellite constellation, will be important in building the next generation of lithospheric field models.
Liu Chang; Deng Na; Liu Rui; Jing Ju; Xu Yan; Wang Shuo; Wang Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Lee, Jeongwoo [Physics Department, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Wiegelmann, Thomas, E-mail: chang.liu@njit.edu [Max Planck Institut fuer Sonnensystemforschung (MPS), Max-Planck-Strasse 2, 37191 Katlenburg-Lindau (Germany)
2012-01-20
The rapid, irreversible change of the photospheric magnetic field has been recognized as an important element of the solar flare process. This Letter reports such a rapid change of magnetic fields during the 2011 February 13 M6.6 flare in NOAA AR 11158 that we found from the vector magnetograms of the Helioseismic and Magnetic Imager (HMI) with 12 minute cadence. High-resolution magnetograms of Hinode that are available at {approx}-5.5, -1.5, 1.5, and 4 hr relative to the flare maximum are used to reconstruct a three-dimensional coronal magnetic field under the nonlinear force-free field (NLFFF) assumption. UV and hard X-ray images are also used to illuminate the magnetic field evolution and energy release. The rapid change is mainly detected by HMI in a compact region lying in the center of the magnetic sigmoid, where the mean horizontal field strength exhibited a significant increase of 28%. The region lies between the initial strong UV and hard X-ray sources in the chromosphere, which are cospatial with the central feet of the sigmoid according to the NLFFF model. The NLFFF model further shows that strong coronal currents are concentrated immediately above the region, and that, more intriguingly, the coronal current system underwent an apparent downward collapse after the sigmoid eruption. These results are discussed in favor of both the tether-cutting reconnection producing the flare and the ensuing implosion of the coronal field resulting from the energy release.
NASA Astrophysics Data System (ADS)
Kother, L. K.; Hammer, M. D.; Finlay, C. C.; Olsen, N.
2014-12-01
We present a technique for modelling the lithospheric magnetic field based on estimation of equivalent potential field sources. As a first demonstration we present an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010. Three component vector field data are utilized at all latitudes. Estimates of core and large-scale magnetospheric sources are removed from the satellite measurements using the CHAOS-4 model. Quiet-time and night-side data selection criteria are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid with an increasing grid resolution towards the airborne survey area. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model regularization (either quadratic or maximum entropy) and Huber weighting. Data error covariance matrices are implemented, accounting for the dependence of data error variances on quasi-dipole latitudes. Results show good consistency with the CM5 and MF7 models for spherical harmonic degrees up to n = 95. Advantages of the equivalent source method include its local nature and the ease of transforming to spherical harmonics when needed. The method can also be applied in local, high resolution, investigations of the lithospheric magnetic field, for example where suitable aeromagnetic data is available. To illustrate this possibility, we present preliminary results from a case study combining satellite measurements and local airborne scalar magnetic measurements of the Norwegian coastline.
A Bayesian hierarchical factorization model for vector fields.
Li, Jun; Tao, Dacheng
2013-11-01
Factorization-based techniques explain arrays of observations using a relatively small number of factors and provide an essential arsenal for multi-dimensional data analysis. Most factorization models are, however, developed on general arrays of scalar values. For a class of practical data arising from observing spatial signals including images, it is desirable for a model to consider general observations, e.g., handling a vector field and non-exchangeable factors, e.g., handling spatial connections between the columns and the rows of the data. In this paper, a probabilistic model for factorization is proposed. We adopt Bayesian hierarchical modeling and treat the factors as latent random variables. A Markov structure is imposed on the distribution of factors to account for the spatial connections. The model is designed to represent vector arrays sampled from fields of continuous domains. Therefore, a tailored observation model is developed to represent the link between the factor product and the data. The proposed technique has been shown effective in analyzing optical flow fields computed on both synthetic images and real-life videoclips. PMID:23893727
Mass Structure of Axial Vector Types of Leptons and Fields
Rasulkhozha S. Sharafiddinov
2011-04-19
A classification of currents with respect to C-operation admits the existence of C-noninvariant types of Dirac fermions. Among them one can meet an electroweakly charged C-antisymmetrical leptons, the mass of which includes the electric and weak components responsible for the existence of their anapole charge, charge radius and electric dipole moment. Such connections can constitute the paraleptons of axial-vector currents, for example, at the interactions with field of spinless nuclei of true neutrality. We derive the united equations which relate the structural parts of mass to anapole, charge radius and electric dipole of any truly neutral lepton in the framework of flavour symmetry. Thereby, they establish the C-odd nature of leptons and fields at the level of constancy law of the size implied from the multiplication of a weak mass of C-antisymmetrical lepton by its electric mass. Therefore, all leptons of C-antisymmetricality regardless of the difference in masses of an axial-vector character, have the same anapole with his radius as well as an equal electric dipole. Their analysis together with measured value of an electric dipole moment of lepton gives the right to interpret not only the existence of truly neutral types of leptons and fields but also the availability of mass structure in them as the one of earlier laboratory facts.
Construction of Solar-Wind-Like Magnetic Fields
NASA Technical Reports Server (NTRS)
Roberts, Dana Aaron
2012-01-01
Fluctuations in the solar wind fields tend to not only have velocities and magnetic fields correlated in the sense consistent with Alfven waves traveling from the Sun, but they also have the magnitude of the magnetic field remarkably constant despite their being broadband. This paper provides, for the first time, a method for constructing fields with nearly constant magnetic field, zero divergence, and with any specified power spectrum for the fluctuations of the components of the field. Every wave vector, k, is associated with two polarizations the relative phases of these can be chosen to minimize the variance of the field magnitude while retaining the\\random character of the fields. The method is applied to a case with one spatial coordinate that demonstrates good agreement with observed time series and power spectra of the magnetic field in the solar wind, as well as with the distribution of the angles of rapid changes (discontinuities), thus showing a deep connection between two seemingly unrelated issues. It is suggested that using this construction will lead to more realistic simulations of solar wind turbulence and of the propagation of energetic particles.
The flexible magnetic field thruster
NASA Technical Reports Server (NTRS)
Brophy, J. R.; Wilbur, P. J.
1982-01-01
The thruster is designed so that ion currents to various internal surfaces can be measured directly; these measurements facilitate calculations of the distribution of ion currents inside the discharge chamber. Experiments are described suggesting that the distribution of ion currents inside the discharge chamber is strongly dependent on the shape and strength of the magnetic field but independent of the discharge current, discharge voltage, and neutral flow rate. Measurements of the energy cost per plasma ion suggest that this cost decreases with increasing magnetic field strength as a consequence of increased anode shielding from the primary electrons. Energy costs per argon plasma ion as low as 50 eV are measured. The energy cost per beam ion is found to be a function of the energy cost per plasma ion, extracted ion fraction, and discharge voltage. Part of the energy cost per beam ion has to do with creating many ions in the plasma and then extracting only a fraction of them into the beam. The balance of the energy goes into accelerating the remaining plasma ions into the walls of the discharge chamber.
Formal averaging of quasi-periodic vector fields Ander Murua
Murua, Ander
the quasi-periodic vector field d dt y = f (y, t) = kZ d ei(k·)t fk(y). there exists a formal quasi-periodic change of variables y = K(Y , t) that transforms the QP system into d dt Y = F1(Y ) + 2 F2(Y·)tfk(y), y(t) = y(0) + uT u(t) u Fu(y(0)), T is the set of rooted trees labelled by k Z d , and for each u
Cyclicity of a fake saddle inside the quadratic vector fields
NASA Astrophysics Data System (ADS)
De Maesschalck, P.; Rebollo-Perdomo, S.; Torregrosa, J.
2015-01-01
This paper concerns the study of small-amplitude limit cycles that appear in the phase portrait near an unfolded fake saddle singularity. This degenerate singularity is also known as an impassable grain. The canonical form of the unperturbed vector field is like a degenerate flow box. Near the singularity, the phase portrait consists of parallel fibers, all but one of which have no singular points, and at the singular fiber, there is one node. We demonstrate different techniques in order to show that the cyclicity is bigger than or equal to two when the canonical form is quadratic.
Semiconductor Crystal Growth in Static and Rotating Magnetic fields
NASA Technical Reports Server (NTRS)
Volz, Martin
2004-01-01
Magnetic fields have been applied during the growth of bulk semiconductor crystals to control the convective flow behavior of the melt. A static magnetic field established Lorentz forces which tend to reduce the convective intensity in the melt. At sufficiently high magnetic field strengths, a boundary layer is established ahead of the solid-liquid interface where mass transport is dominated by diffusion. This can have a significant effect on segregation behavior and can eliminate striations in grown crystals resulting from convective instabilities. Experiments on dilute (Ge:Ga) and solid solution (Ge-Si) semiconductor systems show a transition from a completely mixed convective state to a diffusion-controlled state between 0 and 5 Tesla. In HgCdTe, radial segregation approached the diffusion limited regime and the curvature of the solid-liquid interface was reduced by a factor of 3 during growth in magnetic fields in excess of 0.5 Tesla. Convection can also be controlled during growth at reduced gravitational levels. However, the direction of the residual steady-state acceleration vector can compromise this effect if it cannot be controlled. A magnetic field in reduced gravity can suppress disturbances caused by residual transverse accelerations and by random non-steady accelerations. Indeed, a joint program between NASA and the NHMFL resulted in the construction of a prototype spaceflight magnet for crystal growth applications. An alternative to the suppression of convection by static magnetic fields and reduced gravity is the imposition of controlled steady flow generated by rotating magnetic fields (RMF)'s. The potential benefits of an RMF include homogenization of the melt temperature and concentration distribution, and control of the solid-liquid interface shape. Adjusting the strength and frequency of the applied magnetic field allows tailoring of the resultant flow field. A limitation of RMF's is that they introduce deleterious instabilities above a critical magnetic field value. Growth conditions in which static magnetic fields rotational magnetic fields, and reduced gravitational levels can have a beneficial role will be described.
Impact of a static magnetic field on high-order harmonic spectra
Fischer, R.; Keitel, C. H.; Jung, R.; Pretzler, G.; Willi, O. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg (Germany); Institut fuer Laser- und Plasmaphysik, Heinrich-Heine-Universitaet Duesseldorf, Universitaetsstr. 1, D-40225 Duesseldorf (Germany)
2007-03-15
We have studied the influence of a static magnetic field on the high harmonic radiation that is caused by the motion of an atomic electron along the laser propagation direction. Different from the ordinary high harmonic spectrum which has been studied under the influence of a static magnetic field, we found that the spectrum of the harmonic radiation polarized in the laser propagation direction is quite sensitive to an additional static magnetic field. The signal heights of this spectrum can be substantially affected by a relatively weak static magnetic field of the order of 30 T directed along the magnetic-field vector of the linearly polarized laser pulse. This dependence of the signal strength on the external magnetic field has clear potential to be employed as a means to measure magnetic fields.
Bipolar pulse field for magnetic refrigeration
Lubell, Martin S. (Oak Ridge, TN)
1994-01-01
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.
Exploring Magnetic Fields in Your Environment
NSDL National Science Digital Library
This is a lesson about measuring magnetic field directions of Earth and in the environment. First, learners go outside, far away from buildings, power lines, or anything electrical or metal, and use compasses to identify magnetic North. Next, they use the compasses to probe whether there are any sources of magnetic fields in the local environment, including around electronic equipment such as a CD player and speakers. This is the first lesson in the second session of the Exploring Magnetism teacher guide.
A carpet cloak for static magnetic field
NASA Astrophysics Data System (ADS)
Wang, Rongfeng; Lei Mei, Zhong; Jun Cui, Tie
2013-05-01
We present a two-dimensional carpet cloak for static magnetic field, a design that renders the magnetic response of a given volume invisible from its exterior, without altering the external magnetic fields. The device is designed using transformation optics method and can be implemented with alternating superconducting and magnetic material layers. Through the proper design of the constitutive tensors and relative thicknesses of each slab, we achieve the perfect performance of invisibility. Full wave numerical simulations confirm our design.
Magnetic Fields and Rotations of Protostars
Masahiro N. Machida; Shu-ichiro Inutsuka; Tomoaki Matsumoto
2007-07-21
The evolution of the magnetic field and angular momentum in the collapsing cloud core is studied using three-dimensional resistive MHD nested grid simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic field, we calculate the cloud evolution from the molecular cloud core (n=10^4 cm^-3) to the stellar core (n \\simeq 10^22 cm^-3). The magnetic field strengths at the center of the clouds converge to a certain value as the clouds collapse, when the clouds have the same angular momenta but different strengths of the magnetic fields at the initial state. For 10^12 cm^-3 magnetic field from the collapsing cloud core, and the magnetic field lines, which are strongly twisted for n magnetic field lines are twisted and amplified again for nc > 10^16 cm^-3, because the magnetic field is recoupled with the warm gas. Finally, protostars at their formation epoch have 0.1-1kG of the magnetic fields, which are comparable to observations. The magnetic field strength of protostar slightly depends on the angular momentum of the host cloud. The protostar formed from the slowly rotating cloud core has a stronger magnetic field. The evolution of the angular momentum is closely related to the evolution of the magnetic field. The angular momentum in the collapsing cloud is removed by the magnetic effect. The formed protostars have 0.1-2 days of the rotation period at their formation epoch, which are slightly shorter than the observation. This indicates that the further removal mechanism of the angular momentum such as interaction between the protostar and disk, wind gas or jet is important in further evolution of the protostar.
Self Magnetic Field and Current-loop of Electron with Five Different Radii and Intrinsic Properties
S. Ghosh; M. R. Devi; A. Choudhury; J. K. Sarma
2009-01-01
With the rotation of charge in a circular path current-loop is generated.\\u000aThis results in the production of magnetic fields in a charged body. This self\\u000a(internal) magnetic field is treated here with five different radii of\\u000aelectron. Closed loop line integral of magnetic induction vector or the\\u000aintegral form of the Ampere's circuital law is expressed in terms intrinsic
Self Magnetic Field and Current-loop of Electron with Five Different Radii and Intrinsic Properties
S. Ghosh; M. R. Devi; A. Choudhury; J. K. Sarma
2009-12-09
With the rotation of charge in a circular path current-loop is generated. This results in the production of magnetic fields in a charged body. This self (internal) magnetic field is treated here with five different radii of electron. Closed loop line integral of magnetic induction vector or the integral form of the Ampere's circuital law is expressed in terms intrinsic properties of electron.
Frey, Pascal
provide analysts with increasingly large vector data sets. This raw data must next be properly conveyedC1-Interpolation for Vector Field Topology Visualization Gerik Scheuermann Xavier Tricoche Hans An application of scalar interpolation for 2D vector field topol- ogy visualization is presented. Powell
Plasma and Magnetic Field Inside Magnetic Clouds: a Global Study
C. Cid; M. A. Hidalgo; T. Nieves-Chinchilla; J. Sequeiros; A. F. Viñas
2002-01-01
Data observed during spacecraft encounters with magnetic clouds have been extensively analyzed in the literature. Moreover, several models have been proposed for the magnetic topology of these events, and fitted to the observations. Although these interplanetary events present well-defined plasma features, none of those models have included a simultaneous analysis of magnetic field and plasma data. Using as a starting
NASA Astrophysics Data System (ADS)
Sayanagi, K.; Isezaki, N.; Matsuo, J.; Harada, M.; Kasaya, T.
2011-12-01
Geophysical surveys near the seafloor are very effective methods in order to investigate fine structures of the oceanic crust. Such surveys have increased in researches and developments of the seafloor, and will be more and more necessary in the future. For example, seabed resources like hydrothermal deposits have recently focused attention behind the international situation for natural resources like a competition of resources development. In order to estimate accurate abundance of those resources, the above detailed investigations should be needed because of low resolution of geophysical surveys on the sea and low efficiency of exploratory drilling. From such a viewpoint, we have been developing a measurement system for magnetic explorations using an AUV and a deep-tow system. The magnetic exploration system consists of two 3-axis flux-gate magnetometers, one/two Overhauser magnetometer(s), an optical fiber gyro, a main unit (control, communication, recording), and an onboard unit. These devices except for the onboard unit are installed in pressure cases (depth limit: 6000m). Thus this system can measure three components and total intensity of the geomagnetic field in the deep sea. In 2009, the first test of the magnetic exploration system was carried out in the Kumano Basin using AUV Urashima and towing vehicle Yokosuka Deep-Tow during the R/V Yokosuka YK09-09 cruise. In this test, we sank a small magnetic target to the seafloor, and examined how the system worked. As a result, we successfully detected magnetic anomaly of the target to confirm the expected performance of that in the sea. In 2010, the magnetic exploration system was further tested in the Bayonnaise Knoll area both using a titanium towing frame during the R/V Bosei-maru cruise and using AUV Urashima during the R/V Yokosuka YK10-17 cruise. The purpose of these tests was to evaluate the performance of the system in an actual hydrothermal deposit area for practical applications of that. The Bayonnaise Knoll is a submarine caldera with an outer rim of 2.5-3 km and a floor of 840-920 m, which is located in the Izu-Ogasawara arc. A large hydrothermal deposit, Hakurei deposit, lies in the southeast part of the caldera. In the R/V Bosei-maru cruise, we observed three components of magnetic anomalies at depths of 400-570 m along SE-NW and WE tracks across the caldera. In the R/V Yokosuka YK10-17 cruise, we observed three components and total intensity of magnetic anomalies at altitudes of 60-100 m around the Hakurei deposit and at depth of 500 m above the caldera. The analysis of these data is now energetically pushed forward. A 3D gridded data set of the vector magnetic anomaly in the latter cruise was made by solving the Laplace's equation in the areas where observation data were not available, which is the unique procedure for analysis of the vector anomalies. Several magnetization solutions have been so far obtained by successive approximation and inversion methods. We will here present the measurement of the geomagnetic field and analysis of magnetization structure in Bayonnaise Knoll caldera. Note that this study has been supported by the Ministry of Education, Culture, Sports, Science & Technology (MEXT).
Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane
NASA Technical Reports Server (NTRS)
Pant, Bharat B. (Inventor); Wan, Hong (Inventor)
2001-01-01
A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.
DC-based magnetic field controller
Kotter, D.K.; Rankin, R.A.; Morgan, J.P.
1994-05-31
A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.
DC-based magnetic field controller
Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)
1994-01-01
A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.
Liu, Chang; Liu, Rui; Lee, Jeongwoo; Wiegelmann, Thomas; Jing, Ju; Xu, Yan; Wang, Shuo; Wang, Haimin
2011-01-01
The rapid, irreversible change of the photospheric magnetic field has been recognized as an important element of the solar flare process. This Letter reports such a rapid change of magnetic fields during the 2011 February 13 M6.6 flare in NOAA AR 11158 that we found from the vector magnetograms of the Helioseismic and Magnetic Imager with 12-min cadence. High-resolution magnetograms of Hinode that are available at ~-5.5, -1.5, 1.5, and 4 hrs relative to the flare maximum are used to reconstruct three-dimensional coronal magnetic field under the nonlinear force-free field (NLFFF) assumption. UV and hard X-ray images are also used to illuminate the magnetic field evolution and energy release. The rapid change is mainly detected by HMI in a compact region lying in the center of the magnetic sigmoid, where the mean horizontal field strength exhibited a significant increase by 28%. The region lies between the initial strong UV and hard X-ray sources in the chromosphere, which are cospatial with the central feet of...
Static uniform magnetic fields and amoebae
Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A. [Tennessee Technological Univ., Cookeville, TN (United States)] [Tennessee Technological Univ., Cookeville, TN (United States)
1997-03-01
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.
Development of marine magnetic vector measurement system using AUV and deep-towed vehicle
NASA Astrophysics Data System (ADS)
Sayanagi, K.; Isezaki, N.; Matsuo, J.; Harada, M.; Kasaya, T.; Nishimura, K.; Baba, H.
2012-04-01
Marine magnetic survey is one of useful methods in order to investigate the nature of the oceanic crust. Most of the data are, however, intensity of the geomagnetic field without its direction. Therefore we cannot properly apply a physical formula describing the relation between magnetic field and magnetization to analyses of the data. With this problem, Isezaki (1986) developed a shipboard three-component magnetometer which measures the geomagnetic vector at the sea. On the other hand, geophysical surveys near the seafloor have been more and more necessary in order to show the details of the oceanic crust. For instance, development of seabed resources like hydrothermal deposits needs higher resolution surveys compared with conventional surveys at the sea for accurate estimation of abundance of the resources. From these viewpoints, we have been developing a measurement system of the deep-sea geomagnetic vector using AUV and deep-towed vehicle. The measurement system consists of two 3-axis flux-gate magnetometers, an Overhauser magnetometer, an optical fiber gyro, a main unit (control, communication, recording), and an onboard unit. These devices except for the onboard unit are installed in pressure cases (depth limit: 6000m). Thus this measurement system can measure three components and intensity of the geomagnetic field in the deep-sea. In 2009, the first test of the measurement system was carried out in the Kumano Basin using AUV Urashima and towing vehicle Yokosuka Deep-Tow during the R/V Yokosuka YK09-09 cruise. In this test, we sank a small magnetic target to the seafloor, and examined how the system worked. As a result, we successfully detected magnetic anomaly of the target to confirm the expected performance of that in the sea. In 2010, the measurement system was tested in the Bayonnaise Knoll area both using a titanium towing frame during the R/V Bosei-maru cruise and using AUV Urashima during the R/V Yokosuka YK10-17 cruise. The purpose of these tests was to evaluate the performance of the system in an actual hydrothermal deposit area for practical applications of that. The Bayonnaise Knoll is a submarine caldera with an outer rim of 2.5-3 km and a floor of 840-920 m, which is located in the Izu-Ogasawara arc. A large hydrothermal deposit, Hakurei deposit lies in the southeast part of the caldera. In the R/V Bosei-maru cruise, we observed three components of magnetic anomalies at depths of 400-570 m along SE-NW and WE tracks across the caldera. In the R/V Yokosuka YK10-17 cruise, we observed three components and intensity of magnetic anomalies at altitudes of 60-100 m around the Hakurei deposit and at depth of 500 m above the caldera. From these tests, we have succeeded in measuring the geomagnetic vector and intensity using the AUV and the deep-towed vehicle, and also have obtained detailed magnetic anomaly in the Hakurei deposit area. We will here present the outlines of the measurement system and the tests in the sea. Note that this study has been supported by the Ministry of Education, Culture, Sports, Science & Technology (MEXT).
Nonhelical inverse transfer of a decaying turbulent magnetic field.
Brandenburg, Axel; Kahniashvili, Tina; Tevzadze, Alexander G
2015-02-20
In the presence of magnetic helicity, inverse transfer from small to large scales is well known in magnetohydrodynamic (MHD) turbulence and has applications in astrophysics, cosmology, and fusion plasmas. Using high resolution direct numerical simulations of magnetically dominated self-similarly decaying MHD turbulence, we report a similar inverse transfer even in the absence of magnetic helicity. We compute for the first time spectral energy transfer rates to show that this inverse transfer is about half as strong as with helicity, but in both cases the magnetic gain at large scales results from velocity at similar scales interacting with smaller-scale magnetic fields. This suggests that both inverse transfers are a consequence of universal mechanisms for magnetically dominated turbulence. Possible explanations include inverse cascading of the mean squared vector potential associated with local near two dimensionality and the shallower k^{2} subinertial range spectrum of kinetic energy forcing the magnetic field with a k^{4} subinertial range to attain larger-scale coherence. The inertial range shows a clear k^{-2} spectrum and is the first example of fully isotropic magnetically dominated MHD turbulence exhibiting weak turbulence scaling. PMID:25763960
Multiresolution and Explicit Methods for Vector Field Analysis and Visualization
NASA Technical Reports Server (NTRS)
Nielson, Gregory M.
1997-01-01
This is a request for a second renewal (3d year of funding) of a research project on the topic of multiresolution and explicit methods for vector field analysis and visualization. In this report, we describe the progress made on this research project during the second year and give a statement of the planned research for the third year. There are two aspects to this research project. The first is concerned with the development of techniques for computing tangent curves for use in visualizing flow fields. The second aspect of the research project is concerned with the development of multiresolution methods for curvilinear grids and their use as tools for visualization, analysis and archiving of flow data. We report on our work on the development of numerical methods for tangent curve computation first.
Extraterrestrial Magnetic Fields: Achievements and Opportunities
EDWARD J. SMITHAND; Charles Sonett
1976-01-01
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
Magnetic field effects on plasma ionization balance
Weisheit, J.C.
1995-12-31
Magnetic fields give rise to several phenomena that can significantly affect ionization balance in a plasma. Theoretical models commonly used to determine the charge state distribution (viz.,
Origin of magnetic fields in galaxies
Rafael S. de Souza; Reuven Opher
2010-01-01
Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial Universe (assumed to be random), predicted by the fluctuation -dissipation theorem, predicts ˜0.034muG fields over ˜0.3kpc regions in galaxies. If the dipole magnetic
Magnetic field sensor utilizing bent fiber taper and magnetic fluid
NASA Astrophysics Data System (ADS)
Li, Jie; Tian, Zhuang; Sun, Li-Peng; Guan, Bai-Ou
2014-05-01
A magnetic field sensor is demonstrated by placing a bent-fiber taper modal interferometer inside a magnetic fluid sealed with an organic glass base. Owing to the strong refractive index dependency of the interferometer and magneto-optics property of the fluid, our sensor exhibits high sensitivity to the external magnetic field change. A linear wavelength dependency of ~58pm/Oe is experimentally obtained within a magnetic field range from 30 to 80 Oe. Our structure is featured of high sensitivity, fiber-compatibility, compactness, and robustness.
Jur?išinová, E; Jur?išin, M; Zalom, P
2014-04-01
Using the field-theoretic renormalization group technique in the two-loop approximation, the influence of helicity (spatial parity violation) on the turbulent vector Prandtl number is investigated in the model of a passive vector field advected by the turbulent helical environment driven by the stochastic Navier-Stokes equation. It is shown that the presence of helicity in the turbulent environment can significantly decrease the value of the turbulent vector Prandtl number by up to 15% of its nonhelical value. This result is compared to the corresponding results obtained recently for the turbulent Prandtl number of a passively advected scalar quantity as well as for the turbulent magnetic Prandtl number of a weak magnetic field in the framework of the kinematic magnetohydrodynamic turbulence. It is shown that the behavior of the turbulent vector Prandtl number as function of the helicity parameter is much closer to the corresponding behavior of the turbulent Prandtl number of the scalar quantity than to the behavior of the turbulent magnetic Prandtl number. PMID:24827348
Minimizing magnetic fields for precision experiments
NASA Astrophysics Data System (ADS)
Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S.; Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.
2015-06-01
An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.
Minimizing magnetic fields for precision experiments
Altarev, I; Lins, T; Marino, M G; Nießen, B; Petzoldt, G; Reisner, M; Stuiber, S; Sturm, M; Singh, J T; Taubenheim, B; Rohrer, H K; Schläpfer, U
2015-01-01
An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.
Screening magnetic fields by superconductors: A simple model
Caputo, J.-G., E-mail: caputo@insa-rouen.fr [Laboratoire de Mathématiques, INSA de Rouen, Avenue de l'Université, 76801 Saint-Etienne du Rouvray (France); Gozzelino, L.; Laviano, F.; Ghigo, G.; Gerbaldo, R. [Department of Applied Science and Technology, Politecnico di Torino, 10129, Torino (Italy); Noudem, J.; Thimont, Y.; Bernstein, P. [CRISMAT/LUSAC, Physics Department, Université de Caen (France)
2013-12-21
We introduce a simple approach to evaluate the magnetic field distribution around superconducting samples, based on the London equations; the elementary variable is the vector potential. This procedure has no adjustable parameters, only the sample geometry and the London length, ?, determine the solution. This approach was validated by comparing the induction field calculated to the one measured above MgB{sub 2} disks of different diameters, at 20?K and for applied fields lower than 0.4?T. The model can be applied if the flux line penetration inside the sample can be neglected when calculating the induction field distribution outside the superconductor. We conclude by showing on a cup-shape geometry how one can design a magnetic shield satisfying a specific constraint.
Magnetic field properties of SSC model dipole magnets
Wake, M.; Bossert, R.; Carson, J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Lamm, M.J.; Strait, J. (Fermi National Accelerator Lab., Batavia, IL (United States)); Butteris, J.; Sims, R.; Winters, M. (Superconducting Super Collider Lab., Dallas, TX (United States))
1992-09-01
SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.
Magnetic Resonance Imaging System Based on Earth's Magnetic Field
Stepi?nik, Janez
of the magnetic field enables scanning of very large volume samples. Reduction in S/N ratio due to the weak in the case of strong magnetic fields, detection and processing of low frequency signal are less 655 DOI: 10 Vol. 32, No. 6, pp. 655667, 2004 #12;demanding for the electronics. The techniques used
Magnetic field waves at Uranus
NASA Technical Reports Server (NTRS)
Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.
1991-01-01
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 (SwRI), and Goddard Space Flight Center (GSFC). In addition, other collaborations have been formed with investigators granted UDAP funds for similar studies and with investigators affiliated with other Voyager experiments. These investigations and the corresponding collaborations are included in the report. The proposed effort as originally conceived included an examination of waves downstream from the shock within the magnetosheath. However, the observations of unexpected complexity and diversity within the upstream region have necessitated that we confine our efforts to those observations recorded upstream of the bow shock on the inbound and outbound legs of the encounter by the Voyager 2 spacecraft.
Magnetic monopole field exposed by electrons
NASA Astrophysics Data System (ADS)
Béché, Armand; van Boxem, Ruben; van Tendeloo, Gustaaf; Verbeeck, Jo
2014-01-01
The experimental search for magnetic monopole particles has, so far, been in vain. Nevertheless, these elusive particles of magnetic charge have fuelled a rich field of theoretical study. Here, we created an approximation of a magnetic monopole in free space at the end of a long, nanoscopically thin magnetic needle. We experimentally demonstrate that the interaction of this approximate magnetic monopole field with a beam of electrons produces an electron vortex state, as theoretically predicted for a true magnetic monopole. This fundamental quantum mechanical scattering experiment is independent of the speed of the electrons and has consequences for all situations where electrons meet such monopole magnetic fields, as, for example, in solids. The set-up not only shows an attractive way to produce electron vortex states but also provides a unique insight into monopole fields and shows that electron vortices might well occur in unexplored solid-state physics situations.
Ferroelectric Cathodes in Transverse Magnetic Fields
Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch
2002-07-29
Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode.
Magnetic fields in anisotropic relativistic stars
NASA Astrophysics Data System (ADS)
Folomeev, Vladimir; Dzhunushaliev, Vladimir
2015-02-01
Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.
Magnetic Fields in the Milky Way
NASA Astrophysics Data System (ADS)
Haverkorn, Marijke
This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.
Magnetic fields in anisotropic relativistic stars
Vladimir Folomeev; Vladimir Dzhunushaliev
2015-02-28
Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.
Nuclear magnetic resonances in weak fields
Mitchell, Richard Warren
1953-01-01
?s technique involves ~ su41ng a molecular beam through tuo sueeessive static magnetic fields shish have gradients in opposite direotions, While passing from ene magnetic field ts tho other~ the beam is irradiated eith electro-mag- nstio ?nsrgy? When tho...Lgneto The ssmple was placed in, the best pert of the field Then a permanent magnet was brought close to the solenoid& snd pointed to a spot gust beyond the sample in such a manner that, the field of the permanent magnet was roughly opposibx to that...
Killing Vector Fields, Maxwell Equations and Lorentzian Spacetimes
Waldyr A. Rodrigues Jr
2008-08-13
In this paper we first analyze the structure of Maxwell equations in a Lorentzian spacetime where the potential A is proportional to 1-form K physically equivalent to a Killing vector field (supposed to exist). We show that such A obeys the Lorenz gauge and also a wave equation that can be written in terms of the covariant D'Alembertian or the Ricci operator. Moreover, we determine the correct current defined by that potential showing that it is of superconducting type, being two times the product of the components of A by the Ricci 1-form fields. We also study the structure of the spacetime generated by the coupled system consisting of a electromagnetic field F = dA (A, as above), an ideal charged fluid with dynamics described by an action function S and the gravitational field. We show that Einstein equations in this situation is then equivalent to Maxwell equations with a current givn by fFAF (the product meaning the Clifford product of the corresponding form fields), where f is a scalar function which satisfies a well determined algebraic quadratic equation.
Generation of the magnetic field in jets
V. Urpin
2006-05-22
We consider dynamo action under the combined influence of turbulence and large-scale shear in sheared jets. Shear can stretch turbulent magnetic field lines in such a way that even turbulent motions showing mirror symmetry become suitable for generation of a large-scale magnetic field. We derive the integral induction equation governing the behaviour of the mean field in jets. The main result is that sheared jets may generate a large-scale magnetic field if shear is sufficiently strong. The generated mean field is mainly concentrated in a magnetic sheath surrounding the central region of a jet, and it exhibits sign reversals in the direction of the jet axis. Typically, the magnetic field in a sheath is dominated by the component along the jet that can reach equipartition with the kinetic energy of particles, The field in the central region of jets has a more disordered structure.
Three Dimensional Probability Distributions of the Interplanetary Magnetic Field
NASA Astrophysics Data System (ADS)
Podesta, J. J.
2014-12-01
Empirical probability density functions (PDFs) of the interplanetary magnetic field (IMF) have been derived from spacecraft data since the early years of the space age. A survey of the literature shows that past studies have investigated the separate Cartesian components of the magnetic field, the vector magnitude, and the direction of the IMF by means of one-dimensional or two-dimensional PDFs. But, to my knowledge, there exist no studies which investigate the three dimensional nature of the IMF by means of three dimensional PDFs, either in (Bx,By,Bz)(B_x,B_y,B_z)-coordinates or (BR,BT,BN)(B_R,B_T,B_N)-coordinates or some other appropriate system of coordinates. Likewise, there exist no studies which investigate three dimensional PDFs of magnetic field fluctuations, that is, vector differences bmB(t+?)?bmB(t)bm{B}(t+tau)-bm{B}(t). In this talk, I shall present examples of three dimensional PDFs obtained from spacecraft data that demonstrate the solar wind magnetic field possesses a very interesting spatial structure that, to my knowledge, has not previously been identified. Perhaps because of the well known model of Barnes (1981) in which the magnitude of the IMF remains constant, it may be commonly believed that there is nothing new to learn from a full three dimensional PDF. To the contrary, there is much to learn from the investigation of three dimensional PDFs of the solar wind plasma velocity and the magnetic field, as well as three dimensional PDFs of their fluctuations. Knowledge of these PDFs will not only improve understanding of solar wind physics, it is an essential prerequisite for the construction of realistic models of the stochastic time series measured by a single spacecraft, one of the longstanding goals of space physics research. In addition, three dimensional PDFs contain valuable information about the anisotropy of solar wind fluctuations in three dimensional physical space, information that may help identify the reason why the three dimensional wave vector spectrum of magnetic field fluctuations in the solar wind is not axisymmetric about the direction of the mean magnetic field as recent observations in the ecliptic plane at 1 AU have shown.
Solutions and symmetries of force-free magnetic fields
Tassi, E. [Burning Plasma Research Group, Dipartimento di Energetica and CNISM, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Pegoraro, F. [Dipartimento di Fisica, E. Fermi and CNISM, Pisa (Italy); Cicogna, G. [Dipartimento di Fisica, E. Fermi and INFN, Pisa (Italy)
2008-09-15
New analytical results concerning force-free magnetic fields are presented. A number of examples of exact solutions for two-dimensional nonlinear force-free fields described by the Liouville equation are shown. These include classical solutions, such as, the Gold-Hoyle field and the force-free Harris sheet as special cases. The connection between these solutions and the Lie point symmetries of the Liouville equation is illustrated. Lie point symmetries of the equation describing force-free magnetic fields in helical symmetry in cylindrical geometry are also investigated and an infinitesimal generator that, in the vicinity of the cylinder axis, makes it possible to transform purely radially dependent solutions into helically symmetric solutions, is found. Finally we point out the existence of a formal analogy between the equations for the vector potential components of a class of force-free fields and the equations of motion of a charged particle in a magnetic field. This analogy makes it possible to transfer known results from the theory of the motion of a charged particle, into the context of force-free magnetic fields. Explicit examples of such application are given.
Reducing Field Distortion in Magnetic Resonance Imaging
NASA Technical Reports Server (NTRS)
Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob
2010-01-01
A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T
Bowman, J D; Methner, M M
2000-12-01
Magnetic field characteristics have been surveyed systematically in six factories with the Multiwave(R) II waveform capture instrument. These six facilities manufactured plastics, pharmaceuticals, cement, liquid air products, aluminum parts, and aluminum-framed filters. The study goals were to survey the physical characteristics of magnetic fields that may be related to biological effects under various interaction mechanisms and to relate those characteristics to the field's sources. From 59 waveform measurements at worker locations near sources, we calculated the extremely low frequency (ELF) and static field magnitudes, their frequency characteristics, and spatial characteristics of the 60Hz component. The RMS vector magnitude of the ELF magnetic field (the usual exposure metric in most studies) had medians ranging from 0.53 to 12.83 microT in the six factories. The static magnetic field magnitudes had medians of 24.2-46.2 microT, which is well below the geomagnetic reference field of 55.0 microT because of shielding from steel structures. The maximum static field was 128.6 microT near a DC motor. The frequency spectra of the most common fields is dominated by 60Hz, and has a median total harmonic distortion equal to 14.8%. The most common higher frequencies are the third, fifth, and second harmonics of 60Hz. However, magnetic fields in these workplaces had many other 60Hz harmonics and non-harmonic frequencies due particularly to electric motors and computer monitors. The 60Hz component magnetic fields have elliptical polarization with median axial ratio of 25.4%. The average proportion of the 60Hz component parallel to the static field vector was 51.5+/-3.0%, which indicates a significant trend towards perpendicular orientation between these two field components. In this survey of only six factories, the Multiwave(R) II measurements documented a wide diversity of complex magnetic field characteristics and non-sinusoidal waveforms. Although these characteristics are important to the various mechanisms postulated to explain biological effects, they are overlooked by the popular exposure assessment methods which only measure the ELF magnitude. Therefore, spot measurements with the Multiwave(R) II or similar waveform capture instruments are necessary for a complete magnetic field exposure assessment. PMID:11108784
Crutcher, Richard M. [Astronomy Department, University of Illinois, Urbana, IL 61801 (United States); Wandelt, Benjamin [UPMC Universite Paris 06, Institut d'Astrophysique de Paris, 98 bis, boulevard Arago, 75014 Paris (France); Heiles, Carl [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Falgarone, Edith [LRA/LERMA, CNRS UMR 8112, Ecole Normale Superieure and Observatoire de Paris, Paris (France); Troland, Thomas H. [Physics and Astronomy Department, University of Kentucky, Lexington, KY 40506 (United States)
2010-12-10
The only direct measurements of interstellar magnetic field strengths depend on the Zeeman effect, which samples the line-of-sight component B{sub z} of the magnetic vector. In this paper, we use a Bayesian approach to analyze the observed probability density function (PDF) of B{sub z} from Zeeman surveys of H I, OH, and CN spectral lines in order to infer a density-dependent stochastic model of the total field strength B in diffuse and molecular clouds. We find that at n < 300 cm{sup -3} (in the diffuse interstellar medium sampled by H I lines), B does not scale with density. This suggests that diffuse clouds are assembled by flows along magnetic field lines, which would increase the density but not the magnetic field strength. We further find strong evidence for B in molecular clouds being randomly distributed between very small values and a maximum that scales with volume density n as B {proportional_to} n {sup 0.65} for n>300 cm{sup -3}, with an uncertainty at the 50% level in the power-law exponent of about {+-}0.05. This break-point density could be interpreted as the average density at which parsec-scale clouds become self-gravitating. Both the uniform PDF of total field strengths and the scaling with density suggest that magnetic fields in molecular clouds are often too weak to dominate the star formation process. The stochasticity of the total field strength B implies that many fields are so weak that the mass/flux ratio in many clouds must be significantly supercritical. A two-thirds power law comes from isotropic contraction of gas too weakly magnetized for the magnetic field to affect the morphology of the collapse. On the other hand, our study does not rule out some clouds having strong magnetic fields with critical mass/flux ratios.
Magnetic phase control by an electric field
Thomas Lottermoser; Thomas Lonkai; Uwe Amann; Dietmar Hohlwein; Jörg Ihringer; Manfred Fiebig
2004-01-01
The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and `spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the
Magnetic Field Mapping by Selective Equipotential Excitation
Ouajdi Felfoul; Michelle Raimbert; Sylvain Martel
2006-01-01
A new magnetic field mapping method in MRI is presented. This technique is ideal for severe inhomogeneities where plane warp cannot be ignored. The present study employs a ferromagnetic ball to create a perturbation within the imaged volume. The magnetic moment and position of the device are acquired experimentally with a new technique that excites magnetic equipotentials within a volume.
LABORATORY VI MAGNETIC FIELDS AND FORCES
Minnesota, University of
. · Calculate the motion of a particle with a constant acceleration. · Calculate the motion of a particle of the universe, the atomic structure of materials, and the quark structure of elementary particles. Magnetic; · Calculate the magnetic force on a charged particle moving in a uniform magnetic field and describe its
The Physics of Attraction and Repulsion: Magnetism and Magnetic Fields
NASA Astrophysics Data System (ADS)
Nakotte, Heinz
2001-11-01
The development of new materials with improved magnetic properties completely changed the modern world in the past decades. Recent progress is predominantly due to a better understanding of magnetism that has gone far beyond compass needles rotating in a magnetic field and bar magnets attracting or repelling each other. New magnetic materials are used to build smaller and smaller read/write heads and hard disks with increased storage capacity, developments that are responsible the revolution in the computer industry. Another example is the field of magnetic levitation that became feasible for commercial applications with the discovery of new superconducting materials, and a prototype train is under development in Japan. In medicine, the development of magnetic resonance imaging (MRI) provides an alternative to other (destructive) radiation techniques.
Liu Guo-zhi; Song Xiao-xin
1998-01-01
The self-magnetic-field-limiting current of intense relativistic electron beam (IREB) without an externally applied magnetic field is reported and briefly commented in this paper. By using dynamic balance method the self-magnetic-field-limiting current of IREB under externally applied magnetic field is derived, showing that in this case it will increase. This result is obtained for the first time, so far as we
NSDL National Science Digital Library
Stern, David P. (David Peter), 1931-
This web page, authored and curated by David P. Stern, introduces vectors as an extension of numbers having both magnitude and direction. The initial motivation is to describe velocity but the material includes a general discussion of vector algebra and an application to forces for the inclined plane. The page contains links to a related lesson plan and further opportunities to explore vectors. This is part of the extensive web site "From Stargazers to Starships", that uses space exploration and space science to introduce topics in physics and astronomy. Translations in Spanish and French are available.
Magnetic field decay in model SSC dipoles
Gilbert, W.S.; Althaus, R.F.; Barale, P.J.; Benjegerdes, R.W.; Green, M.A.; Green, M.I.; Scanlan, R.M.
1988-08-01
We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs.
Yunqiu Wu; Zongxi Tang; Biao Zhang; Yuehang Xu
2007-01-01
A new method is proposed for electromagnetic parameters (permittivity and permeability) measurement. The microstrip transmission-line is used as measure structure, and supported vector machine (SVM) is introduced to extract actual permittivity and permeability of magnetic materials. Experiment results show that both permittivity and permeability of magnetic materials can be extracted accurately.
Measurement of the spin-transfer-torque vector in magnetic tunnel junctions
Loss, Daniel
ARTICLES Measurement of the spin-transfer-torque vector in magnetic tunnel junctions JACK C. SANKEY present direct measurements of both the magnitude and direction of the spin torque in magnetic tunnel with recent predictions for near-perfect spin-polarized tunnelling. We find that the strength of the in
A space vector modulation direct torque control for permanent magnet synchronous motor drive systems
D. Sun; J. G. Zhu; Y. K. He
2003-01-01
To minimize the ripples of the electro-magnetic torque and flux linkage and to fix the variable switching frequency produced in the conventional direct torque control (DTC) system for permanent magnet synchronous motors, this paper proposes a space vector modulation (SVM) DTC concept. Both simulation and experimental results show that the proposed SVM DTC can dramatically improve the steady state performance
Cosmic microwave background polarization signals from tangled magnetic fields.
Seshadri, T R; Subramanian, K
2001-09-01
Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface of the cosmic microwave background radiation. For fields which redshift to a present value of B0 = 3 x 10(-9) G, these vector modes are shown to generate polarization anisotropies of order 0.1-4 microK on small angular scales (500
Graphene Nanoribbon in Sharply Localized Magnetic Fields
Abdulaziz D. Alhaidari; Hocine Bahlouli; Abderrahim El Mouhafid; Ahmed Jellal
2013-03-20
We study the effect of a sharply localized magnetic field on the electron transport in a strip (ribbon) of graphene sheet, which allows to give results for the transmission and reflection probability through magnetic barriers. The magnetic field is taken as a single and double delta type localized functions, which are treated later as the zero width limit of gaussian fields. For both field configurations, we evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.
Coronal magnetic fields produced by photospheric shear
NASA Technical Reports Server (NTRS)
Sturrock, P. A.; Yang, W.-H.
1987-01-01
The magneto-frictional method is used for computing force free fields to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear, by a simple functional form.
Single-layer high field dipole magnets
Vadim V. Kashikhin and Alexander V. Zlobin
2001-07-30
Fermilab is developing high field dipole magnets for post-LHC hadron colliders. Several designs with a nominal field of 10-12 T, coil bore size of 40-50 mm based on both shell-type and block-type coil geometry are currently under consideration. This paper presents a new approach to magnet design, based on simple and robust single-layer coils optimized for the maximum field, good field quality and minimum number of turns.
Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind
NASA Technical Reports Server (NTRS)
Burlaga, L. F.; Barouch, E.
1974-01-01
The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.
Field Corrections of Open MRI Superconducting Magnets
NASA Astrophysics Data System (ADS)
Matsuda, Tetsuya; Ariyoshi, Akihiko; Tanabe, Hajime
We constructed open MRI superconducting magnets with an iron yoke that generates a 0.7T highly uniform magnetic field. A program that compensates for the error field of those magnets was developed that uses linear programming to achieve an optimal arrangement of a large number of small iron shims. Since additional homogeneity compensation near the target value becomes difficult, we also used nonlinear programming. We must evaluate all shim magnetizations precisely by making a 3D finite element shim model. Since, it is impossible to make such shims in a large magnet model, we describe a fast calculation method of shim magnetizations without that model. Homogeneity of 0.35ppm (Vrms) at 35cm Diameter Spherical Volume (DSV), which is the top value of an open MRI magnet, is obtained by applying these methods. The number of correction times were reduced by half of initial manufactured magnets.
Equivalence of periodic magnetic field to uniform magnetic field in electron beam focusing
K. Ura; M. Terada
1966-01-01
The general solution of the electron trajectory equation in a periodic magnetic field is derived in the form of series expansion, assuming laminar electron flow and small perturbation. It is concluded that if the cathode is not very heavily immersed in a magnetic field, beam focusing by a periodic magnetic field would be almost equivalent to that by a uniform
The National High Magnetic Field Laboratory
NASA Astrophysics Data System (ADS)
Jaime, M.; Lacerda, A.; Takano, Y.; Boebinger, G. S.
2006-11-01
The National High Magnetic Field Laboratory, established in 1990 with support from the National Science Foundation, the State of Florida, and the US Department of Energy, is a facility open to external users around the world. The experimental capabilities are distributed in three campuses. In Tallahassee, Florida, continuous magnetic fields are produced by means of superconducting and resistive magnets reaching fields of up to 33T (resistive), and 45T (hybrid). EMR, ICR, and a 900MHz wide bore NMR magnet are also available. The facility in Gainesville, Florida, is devoted to generating extremely low temperatures in the presence of external magnetic fields (15T, down to 0.4mK), and large MRI imaging capabilities. In Los Alamos, New Mexico, a 9 kV-capable capacitor bank and a number of different liquid Nitrogen-cooled resistive magnets produce repetitive pulses up to 75 T and now a single-shot pulsed up to 300T.
Two-axis magnetic field sensor
NASA Technical Reports Server (NTRS)
Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)
2006-01-01
A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.
Coronal holes and solar magnetic fields
NASA Technical Reports Server (NTRS)
Harvey, J. W.; Sheeley, N. R., Jr.
1979-01-01
Since 1972 nearly continuous observations of coronal holes and their associated photospheric magnetic fields have been made using a variety of satellite and ground-based equipment. The present paper reviews the results of comparisons of these data and shows that the structure and evolution of coronal holes is basically governed by the large-scale distribution of photospheric magnetic flux. Nonpolar holes form in the decaying remnants of bipolar magnetic regions in areas with a large-scale flux imbalance. In addition, there is strong indirect evidence that the magnetic field in coronal holes is always open to interplanetary space, but not all open-field regions have associated coronal holes.
Magnetic fields and rotation of spiral galaxies
E. Battaner; H. Lesch; E. Florido
1998-02-02
We present a simplified model in which we suggest that two important galactic problems -the magnetic field configuration at large scales and the flat rotation curve- may be simultaneously explained. A highly convective disc produces a high turbulent magnetic diffusion in the vertical direction, stablishing a merging of extragalactic and galactic magnetic fields. The outer disc may then adquire a magnetic energy gradient very close to the gradient required to explain the rotation curve, without the hypothesis of galactic dark matter. Our model predicts symmetries of the galactic field in noticeable agreement with the large scale structure of our galaxy.
High concentration ferronematics in low magnetic fields
T. Tóth-Katona; P. Salamon; N. Éber; N. Tomašovi?ová; Z. Mitróová; P. Kop?anský
2014-09-05
We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field $B_{bias}$, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that $B_{bias}$ is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.
Harmonic-Killing vector fields C.T.J. Dodson M.Trinidad Perez M.E. VazquezAbal
Dodson, C.T.J.
Harmonic-Killing vector fields C.T.J. Dodson M.Trinidad PÂ´erez M.E. VÂ´azquezÂAbal Preprint date May this class of vector fields, which we call harmonic-Killing vector fields. 2000 Mathematics Subject transformations consists of isometric, affine or conformal maps, a vector field is called respectively Killing
Fluctuating magnetic field induced resonant activation.
Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra
2014-12-14
In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field. PMID:25494726
Black holes with a single Killing vector field: black resonators
Dias, Oscar J C; Way, Benson
2015-01-01
We numerically construct asymptotically anti-de Sitter (AdS) black holes in four dimensions that contain only a single Killing vector field. These solutions, which we coin black resonators, link the superradiant instability of Kerr-AdS to the nonlinear weakly turbulent instability of AdS by connecting the onset of the superradiance instability to smooth, horizonless geometries called geons. Furthermore, they demonstrate non-uniqueness of Kerr-AdS by sharing asymptotic charges. Where black resonators coexist with Kerr-AdS, we find that the black resonators have higher entropy. Nevertheless, we show that black resonators are unstable and comment on the implications for the endpoint of the superradiant instability.
The Unified First law in "Cosmic Triad" Vector Field Scenario
Yi Zhang; Yungui Gong; Zong-Hong Zhu
2011-08-04
In this letter, we try to apply the unified first law to the "cosmic triad" vector field scenario both in the minimal coupling case and in the non-minimalcoupling case. After transferring the non-minimally coupling action in Jordan frame to Einstein frame, the correct dynamical equation (Friedmann equation) is gotten in a thermal equilibrium process by using the already existing entropy while the entropy in the non-minimal coupled "cosmic triad" scenario has not been derived. And after transferring the variables back to Jordan frame, the corresponding Friedmann equation is demonstrated to be correct. For complete arguments, we also calculate the related Misner-Sharp energy in Jordan and Einstein frames.
Magnetic Helicity and Large Scale Magnetic Fields: A Primer
NASA Astrophysics Data System (ADS)
Blackman, Eric G.
2015-05-01
Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. Here I discuss how magnetic helicity has come to help us understand the saturation of and sustenance of large scale dynamos, the need for either local or global helicity fluxes to avoid dynamo quenching, and the associated observational consequences. I also discuss how magnetic helicity acts as a hindrance to turbulent diffusion of large scale fields, and thus a helper for fossil remnant large scale field origin models in some contexts. I briefly discuss the connection between large scale fields and accretion disk theory as well. The goal here is to provide a conceptual primer to help the reader efficiently penetrate the literature.
Decay of positronium in strong magnetic fields
G. Wunner; H. Herold
1979-01-01
We investigate the decay of bound electron-positron pairs (positronium) in strong magnetic fields (of order 1012 Gauss, which are assumed for neutron stars) on the basis of a correct treatment of the two-body problem, thus improving previous work by Carr and Sutherland (1978). We find that, even in the presence of a strong magnetic field, the decay of the ground
Ensemble Solar Global Magnetic Field Modeling
C. J. Henney; C. N. Arge; J. Koller; W. A. Toussaint; S. L. Young; J. W. Harvey
2010-01-01
The ability to forecast geoeffective space weather events is critically dependent on the estimation of the global solar photospheric magnetic field distribution as input to coronal and heliospheric models. Currently, the solar magnetic field can only be recorded for approximately half of the solar surface at any given time. Since the rotation period of the Sun as observed from Earth
Photon-neutrino interactions in magnetic fields
Shaisultanov R
1998-02-28
The low-energy two neutrino-two photon interactions in the presence of homogeneous magnetic field are studied. The cross sections in external magnetic field are shown to be larger than in vacuum by factor $\\sim (m_W /m_e) ^4(B/B_c) ^2$. The energy-loss rate due to the process $\\gamma \\gamma \\to \
Lengthwise field variation in CBA magnets
Willen
1984-01-01
The multipole content of the magnetic field in accelerator superconducting magnets built with a cos theta current distribution inside an iron yoke is determined by the placement of the individual current-carrying turns in the coil, by the location of the coil inside the iron yoke and by the amount of iron saturation at high field. Differences in these parameters cause
Coulomb crystals in the magnetic field
Baiko, D. A. [A.F. Ioffe Physical-Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)
2009-10-15
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 > or approx. 10{sup 14} G). 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.
Line Sink in Uniform Magnetic Field
Jai Prakash Narain; Mahinder S. Uberoi
1971-01-01
The motion of an inviscid, incompressible, and conducting fluid due to a line sink in a uniform strong magnetic field is considered. The solutions show that motion is confined in a narrow region parallel to the magnetic field. Such a motion for a point sink has erroneously been named as a wake or backward jet flow. Finally, the known solution
Directional discontinuities in the interplanetary magnetic field
Leonard F. Burlaga
1969-01-01
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 (˜
On the origins of galactic magnetic fields
A. Borzou; H. R. Sepangi; R. Yousefi; A. H. Ziaie
2009-11-18
We present a five dimensional unified theory of gravity and electromagnetism which leads to modified Maxwell equations, suggesting a new origin for galactic magnetic fields. It is shown that a region with nonzero scalar curvature would amplify the magnetic fields under certain conditions.
Magnetic fields, branes, and noncommutative geometry
Daniela Bigatti; Leonard Susskind
2000-01-01
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
The formation of sunspot penumbra. Magnetic field properties
NASA Astrophysics Data System (ADS)
Rezaei, R.; Bello González, N.; Schlichenmaier, R.
2012-01-01
Aims: We study the magnetic flux emergence and formation of a sunspot penumbra in the active region NOAA 11024. Methods: We simultaneously observed the Stokes parameters of the photospheric iron lines at 1089.6 nm with the TIP and 617.3 nm with the GFPI spectropolarimeters along with broad-band images using G-band and Ca ii K filters at the German VTT. The photospheric magnetic field vector was reconstructed from an inversion of the measured Stokes profiles. Using the AZAM code, we converted the inclination from line-of-sight (LOS) to the local reference frame (LRF). Results: Individual filaments are resolved in maps of magnetic parameters. The formation of the penumbra is intimately related to the inclined magnetic field. No penumbra forms in areas with strong magnetic field strength and small inclination. Within 4.5 h observing time, the LRF magnetic flux of the penumbra increases from 9.7 × 1020 to 18.2 × 1020 Mx, while the magnetic flux of the umbra remains constant at ~3.8 × 1020 Mx. Magnetic flux in the immediate surroundings is incorporated into the spot, and new flux is supplied via small flux patches (SFPs), which on average have a flux of 2-3 × 1018 Mx. The spot's flux increase rate of 4.2 × 1016 Mx s-1 corresponds to the merging of one SFP per minute. We also find that, during the formation of the spot penumbra, a) the maximum magnetic field strength of the umbra does not change; b) the magnetic neutral line keeps the same position relative to the umbra; c) the new flux arrives on the emergence side of the spot while the penumbra forms on the opposite side; d) the average LRF inclination of the light bridges decreases from 50° to 37°; and e) as the penumbra develops, the mean magnetic field strength at the spot border decreases from 1.0 to 0.8 kG. Conclusions: The SFPs associated with elongated granules are the building blocks of structure formation in active regions. During the sunspot formation, their contribution is comparable to the coalescence of pores. Besides a set of critical parameters for the magnetic field, a quiet environment in the surroundings is important for penumbral formation. As remnants of trapped granulation between merging pores, the light bridges are found to play a crucial role in the formation process. They seem to channel the magnetic flux through the spot during its formation. Light bridges are also the locations where the first penumbral filaments form.
Magnetic Fields in Stars: Origin and Impact
NASA Astrophysics Data System (ADS)
Langer, N.
2014-08-01
Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10% of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.
Solar Mean Magnetic Field Observed by GONG
J. W. Harvey; G. Petrie; R. Clark
2009-01-01
The average line-of-sight (LOS) magnetic field of the Sun has been observed for decades, either by measuring the circular polarization across a selected spectrum line using integrated sunlight or by averaging such measurements in spatially resolved images. The GONG instruments produce full-disk LOS magnetic images every minute, which can be averaged to yield the mean magnetic field nearly continuously. Such
Permanent magnet edge-field quadrupole
Tatchyn, Roman O. (Mountain View, CA)
1997-01-01
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.
Dynamical evolution of a vector field perturbation coupling to Einstein tensor
Songbai Chen; Jiliang Jing
2014-12-04
We have investigated the wave dynamics of a vector field perturbation coupling to Einstein tensor in the four-dimensional Reissner-Nordstr\\"{o}m black hole spacetime. Our results show that besides the dependence on the coupling between the vector field and Einstein tensor, the wave dynamic equation of the vector field perturbation strongly depends on the parity of the perturbation itself, which is quite different from that of the usual vector field perturbation without the coupling in the four-dimensional spacetime. Moreover, we also find that the vector field perturbation with odd parity grows with exponential rate if the coupling strength is stronger than certain a critical value. However, the vector field perturbation with even parity always decays in the Reissner-Nordstr\\"{o}m black hole spacetime.
Manipulation of Raman Resonances Using Magnetic Fields
NASA Astrophysics Data System (ADS)
Desavage, Sara A.; Davis, Jon P.; Narducci, Frank A.
2012-06-01
We have theoretically and experimentally studied Raman resonances in multi-level atoms (specifically ^85Rb). Our emphasis has been on varying the relative orientation of the magnetic field with respect to the propagation direction of the Raman fields. We find that, in general, the spectrum consists of up to 11 peaks. By considering selection rules, we show that it is possible to orient the magnetic field so that either a 6 peak spectrum or 5 peak spectrum results, depending on whether the Raman fields contain a polarization component along the magnetic field direction or not. Furthermore, we find that the spectrum is not always symmetric with respect to the magnetically insensitive transition (clock transition). We explore the origins of the asymmetry and the overall shape of the spectra. We will discuss applications to magnetically sensitive atom interferometry.
Processing of polymers in high magnetic fields
Douglas, E.P.; Smith, M.E.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States); Earls, J.D.; Priester, R.D. Jr. [Dow Chemical Co., Freeport, TX (United States)
1996-05-01
Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. This work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing. The liquid crystal thermoset chosen for this study is the diglycidyl ether of dihydroxy-{alpha}-methylstilbene cured with the diamine sulfamilamide. This thermoset has been cured at field strengths up to 18 Tesla.
Chaotic magnetic fields: Particle motion and energization
Dasgupta, Brahmananda [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Li, Gang [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Li, Xiaocan [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
2014-02-11
Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space.
Jur?išinová, E; Jur?išin, M; Remecký, R
2013-07-01
The turbulent Prandtl number in the model of a passive vector field advected by the turbulent environment driven by the stochastic Navier-Stokes equation is studied by using the field theoretic renormalization group technique in the two-loop approximation. It is shown that unlike the turbulent Prandtl number in the model of passively advected scalar field, as well as the turbulent magnetic Prandtl number of passively advected magnetic field in the framework of the kinematic magnetohydrodynamic turbulence, where the two-loop corrections to the corresponding Prandtl numbers are very small (less than 2% of their one-loop values), the two-loop correction to the turbulent Prandtl number of passively advected vector field is considerably larger; namely, it is 27% of its one-loop value. At the same time, the calculated two-loop value of the turbulent vector Prandtl number, Pr(v,t)=0.7307, is surprisingly very close to the two-loop value of the turbulent Prandtl number of passively advected scalar field, Pr(t)=0.7040. PMID:23944403
Initial Results from the Vector Electric Field Investigation on the C/NOFS Satellite
NASA Technical Reports Server (NTRS)
Pfaff, R.; Rowland, D.; Acuna, M.; Le, G.; Farrell, W.; Holzworth, R.; Wilson, G.; Burke, W.; Freudenreich, H.; Bromund, K.; Liebrecht, C.; Martin, S.; Kujawski, J.; Uribe, P.; Fourre, R.; McCarthy, M.; Maynard, N.; Berthelier, J.-J.; Steigies, C.
2009-01-01
Initial results are presented from the Vector Electric Field Investigation (VEFI) on the Air Force Communication/Navigation Outage Forecasting System (C/NOFS) satellite, a mission designed to understand, model, and forecast the presence of equatorial ionospheric irregularities. The VEFI instrument includes a vector DC electric field detector, a fixed-bias Langmuir probe operating in the ion saturation regime, a flux gate magnetometer, an optical lightning detector, and associated electronics including a burst memory. The DC electric field detector has revealed zonal and meridional electric fields that undergo a diurnal variation, typically displaying eastward and outward-directed fields during the day and westward and downward-directed fields at night. In general, the measured DC electric field amplitudes are in the 0.5-2 mV/m range, corresponding to I3 x B drifts of the order of 30-150 m/s. What is surprising is the high degree of large-scale (10's to 100's of km) structure in the DC electric field, particularly at night, regardless of whether well-defined spread-F plasma density depletions are present. The spread-F density depletions and corresponding electric fields that have been detected thus far have displayed a preponderance to appear between midnight and dawn. Associated with the narrow plasma depletions that are detected are broad spectra of electric field and plasma density irregularities for which a full vector set of measurements is available for detailed study. On some occasions, localized regions of low frequency (< 8 Hz) magnetic field broadband irregularities have been detected, suggestive of filamentary currents, although there is no one-to-one correspondence of these waves with the observed plasma density depletions, at least within the data examined thus far. Finally, the data set includes a wide range of ELF/VLF/HF waves corresponding to a variety of plasma waves, in particular banded ELF hiss, whistlers, and lower hybrid wave turbulence triggered by lightning-induced sferics. The VEFI data set represents a treasure trove of measurements that are germane to numerous fundamental aspects of the electrodynamics and irregularities inherent to the Earth's low latitude ionosphere.
Quark condensate in a magnetic field
Shushpanov, I A
1997-01-01
We study the dependence of quark condensate $\\Sigma$ on an external magnetic field. For weak fields, it rises linearly with the field. Pion mass and residue are also shifted so that the Gell-Mann - Oakes - Renner relation is satisfied. In the strong field region, $\\Sigma(H) \\propto (eH)^{3/2}$.
Magnetic fields in Neutron Stars
NASA Astrophysics Data System (ADS)
Viganò, D.; Pons, J. A.; Miralles, J. A.; Rea, N.
2015-05-01
Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.
Warm inflation in presence of magnetic fields
Piccinelli, Gabriella [Centro Tecnológico, FES Aragón, Universidad Nacional Autónoma de México, Avenida Rancho Seco S/N, Bosques de Aragón, Nezahualcóyotl, Estado de México 57130 (Mexico)] [Centro Tecnológico, FES Aragón, Universidad Nacional Autónoma de México, Avenida Rancho Seco S/N, Bosques de Aragón, Nezahualcóyotl, Estado de México 57130 (Mexico); Sánchez, Ángel [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States)] [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States); Ayala, Alejandro; Mizher, Ana Julia [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510 (Mexico)] [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510 (Mexico)
2013-07-23
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.
Auroral vector electric field and particle comparisons. 1: Pre-midnight convection topology
NASA Technical Reports Server (NTRS)
Maynard, N. C.; Evans, D. S.; Maehlum, B.; Egeland, A.
1976-01-01
Polar 3 was launched in northern Norway on January 27, 1974. Traversing nearly 3 deg latitude, the rocket crossed over a stable IBC II auroral arc in the positive bay region and continued north to a convection boundary which was identified as the Harang discontinuity. Measurement of the complete electric field vector, of energetic electrons and of the auroral N+2 and OI emissions were used to study the convection topology in the pre-magnetic-midnight region. A strong anticorrelation was observed between the electric field and the precipitating energetic electrons. The inverted V nature of the electron precipitations at the convection boundary, compared with the lack of such structure over the arc which was within the positive bay region, leads to the conclusion that auroral arcs are likely to be associated with inverted V type precipitation only at or poleward of convection boundaries and their eddy structures.
Modeling and vector control of planar magnetic levitator
Won-Jong Kim; David L. Trumper; Jeffrey H. Lang
1998-01-01
The authors designed and implemented a magnetically levitated stage with large planar motion capability. This planar magnetic levitator employs four novel permanent-magnet linear motors. Each motor generates vertical force for suspension against gravity, as well as a horizontal force for drive. These linear levitation motors can be used as building blocks in the general class of multi-degree-of-freedom motion stages. In
Field Mapping System for Solenoid Magnet
NASA Astrophysics Data System (ADS)
Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.
2007-01-01
A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.
Magnetic-field-controlled reconfigurable semiconductor logic.
Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark
2013-02-01
Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices. PMID:23364687
Compact low field magnetic resonance imaging magnet: Design and optimization
NASA Astrophysics Data System (ADS)
Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.
2000-03-01
Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.