Influence of Induced Magnetic Field on Large-Scale Pulsed MHD Generator

2002 ◽  
Author(s):  
Yuki Koshiba ◽  
Takehiko Matsushita ◽  
Motoo Ishikawa
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Induced Magnetic Field ◽  
Mhd Generator

scholarly journals Depth of origin of ocean-circulation-induced magnetic signals

2018 ◽  
Vol 36 (1) ◽  
pp. 167-180 ◽  
Author(s):  
Christopher Irrgang ◽  
Jan Saynisch-Wagner ◽  
Maik Thomas
Keyword(s):  
Magnetic Field ◽  
Ocean Circulation ◽  
Large Scale ◽  
Ocean Basin ◽  
Ocean Currents ◽  
Induced Magnetic Field ◽  
Electric Currents ◽  
Regional Patterns ◽  
Motional Induction ◽  
Different Depths

Abstract. As the world ocean moves through the ambient geomagnetic core field, electric currents are generated in the entire ocean basin. These oceanic electric currents induce weak magnetic signals that are principally observable outside of the ocean and allow inferences about large-scale oceanic transports of water, heat, and salinity. The ocean-induced magnetic field is an integral quantity and, to first order, it is proportional to depth-integrated and conductivity-weighted ocean currents. However, the specific contribution of oceanic transports at different depths to the motional induction process remains unclear and is examined in this study. We show that large-scale motional induction due to the general ocean circulation is dominantly generated by ocean currents in the upper 2000 m of the ocean basin. In particular, our findings allow relating regional patterns of the oceanic magnetic field to corresponding oceanic transports at different depths. Ocean currents below 3000 m, in contrast, only contribute a small fraction to the ocean-induced magnetic signal strength with values up to 0.2 nT at sea surface and less than 0.1 nT at the Swarm satellite altitude. Thereby, potential satellite observations of ocean-circulation-induced magnetic signals are found to be likely insensitive to deep ocean currents. Furthermore, it is shown that annual temporal variations of the ocean-induced magnetic field in the region of the Antarctic Circumpolar Current contain information about sub-surface ocean currents below 1000 m with intra-annual periods. Specifically, ocean currents with sub-monthly periods dominate the annual temporal variability of the ocean-induced magnetic field. Keywords. Electromagnetics (numerical methods) – geomagnetism and paleomagnetism (geomagnetic induction) – history of geophysics (transport)

Mîcromagnetic Modeling of the Behavior of Magnetostrictive Films under Stress

2003 ◽  
Vol 785 ◽  
Author(s):  
Y. C. Shu ◽  
J. H. Yen
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Domain ◽  
Conventional Approach ◽  
Intrinsic Stress ◽  
Induced Magnetic Field ◽  
Kinematic Constraint ◽  
Strain Compatibility ◽  
Micromagnetic Modeling ◽  
Simulation Results

ABSTRACTWe study the effect of stress on the behavior of magnetostrictive films. Our approach is different from the conventional one which neglects the strain compatibility. Here, we include the kinematic constraint in our micromagnetic model and proposed to use the average to calculate the stress-induced magnetic field. The analytic formulation of magnetostrictive energy is derived which enables us to perform simulation at a large scale with few iteration steps. The simulation results show that the conventional approach is insufficient to predict magnetic domain patterns for materials with large magnetostriction, and the effect of intrinsic stress cannot be neglected.

Screening current induced magnetic field and stress in ultra-high-field magnets using REBCO coated conductors

2021 ◽  
Author(s):  
Yufan Yan ◽  
Yi Li ◽  
Ti-Ming Qu
Keyword(s):  
Magnetic Field ◽  
High Field ◽  
Large Scale ◽  
Field Experiments ◽  
Field Performance ◽  
Coated Conductors ◽  
Induced Magnetic Field ◽  
Ultra High Field ◽  
Mitigation Methods ◽  
Open Question

Abstract Rare-earth-based barium copper oxide (REBCO) coated conductors are promising candidates for the development of ultra-high-field (UHF) magnets, due to its high in-field performance, engineering current density, tensile strength and commercial availability. However, technological challenges pertaining to the large screening currents still remain. The major issues caused by the screening currents in REBCO conductors in UHF applications involve two aspects: the screening current induced magnetic field (SCF), and the screening current induced stress (SCS). In the past decades, extensive research has been devoted to the SCF, offering a variety of possible remedies. With latest advances in the construction and testing of UHF magnets, new observations of the SCF involving REBCO coils were reported. The SCS was identified in recent years and has raised growing concerns. The excessive and highly concentrated Lorentz force, rooted in the high magnetic field and the screening currents, poses threats to the mechanical strength of the REBCO coated conductors. The aim of this paper is to review recent research efforts in understanding and tackling the screening current related technological issues. For the SCF, we focus on the latest observations in high-field experiments and its various mitigation methods. For the SCS, we present recent studies including experimental characterizations, numerical modelling and possible countermeasures. It is still an open question to precisely predict SCS in large-scale HTS magnets. How to minimize the influence of SCF and SCS is one key technical issue for the design of future UHF magnets.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

scholarly journals An 84-μG Magnetic Field in a Galaxy at Z=0.692?

2008 ◽  
Vol 4 (S254) ◽  
pp. 95-96
Author(s):  
Arthur M. Wolfe ◽  
Regina A. Jorgenson ◽  
Timothy Robishaw ◽  
Carl Heiles ◽  
Jason X. Prochaska
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Faraday Rotation ◽  
Large Scale ◽  
Dynamo Model ◽  
Magnetic Field Generation ◽  
Interstellar Gas ◽  
Splitting Technique ◽  
Average Value ◽  
The Magnetic Field

AbstractThe magnetic field pervading our Galaxy is a crucial constituent of the interstellar medium: it mediates the dynamics of interstellar clouds, the energy density of cosmic rays, and the formation of stars (Beck 2005). The field associated with ionized interstellar gas has been determined through observations of pulsars in our Galaxy. Radio-frequency measurements of pulse dispersion and the rotation of the plane of linear polarization, i.e., Faraday rotation, yield an average value B ≈ 3 μG (Han et al. 2006). The possible detection of Faraday rotation of linearly polarized photons emitted by high-redshift quasars (Kronberg et al. 2008) suggests similar magnetic fields are present in foreground galaxies with redshifts z > 1. As Faraday rotation alone, however, determines neither the magnitude nor the redshift of the magnetic field, the strength of galactic magnetic fields at redshifts z > 0 remains uncertain.Here we report a measurement of a magnetic field of B ≈ 84 μG in a galaxy at z =0.692, using the same Zeeman-splitting technique that revealed an average value of B = 6 μG in the neutral interstellar gas of our Galaxy (Heiles et al. 2004). This is unexpected, as the leading theory of magnetic field generation, the mean-field dynamo model, predicts large-scale magnetic fields to be weaker in the past, rather than stronger (Parker 1970).The full text of this paper was published in Nature (Wolfe et al. 2008).

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