Observation of Single Magnetic-Flux Quanta Using Electron Holography

1990 ◽  
Vol 48 (1) ◽  
pp. 210-211
Author(s):  
T. Matsuda ◽  
S. Hasegawa ◽  
J. Endo ◽  
N. Osakabe ◽  
A. Tonomura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Tungsten Wire ◽  
Thin Filament ◽  
Phase Distribution ◽  
Electron Holography ◽  
Practical Applications ◽  
Magnetic Flux Quantum ◽  
Lead Film ◽  
The Magnetic Field

A Magnetic flux quantum (fluxon) penetrating a superconductor plays an important role in both fundamental and practical applications of superconductivity. However, the fluxon has evaded direct observation, because it is shaped like an extremely thin filament in addition to its small flux value, h/2e (=2x10−15Wb). Several methods have already been developed to indirectly observe each filament of flux. One method is Bitter's [1], in which magnetic powder is sprinkled on the superconductor surface. The powder accumulates at the fluxons, and the image is observed by electron microscopy.We have observed the magnetic field of a single fluxon using holographic electron interferometry [2], in which the phase distribution of an electron beam can be measured to a precision of 2Π/50. The schematic diagram of the experiment is shown in Fig. 1. A weak magnetic field is applied perpendicularly to a superconducting lead film. Fiuxons penetrating the film are observed as phase contour fringes through the electron holography process. The sample is prepared by evaporating lead on one side of a thin tungsten wire, which is shown in Fig. 2.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

Application of electron holography to material science studies on magnetic domain states of small particles

1993 ◽  
Vol 51 ◽  
pp. 1028-1029
Author(s):  
T. Hirayama ◽  
Q. Ru ◽  
T. Tanji ◽  
A. Tonomura
Keyword(s):  
Magnetic Field ◽  
Material Science ◽  
Science Studies ◽  
Phase Distribution ◽  
Carbon Film ◽  
Objective Lens ◽  
Electron Holography ◽  
Transform Method ◽  
Transmission Electron ◽  
Thin Carbon

The observation of small magnetic materials is one of the most important applications of electron holography to material science, because interferometry by means of electron holography can directly visualize magnetic flux lines in a very small area. To observe magnetic structures by transmission electron microscopy it is important to control the magnetic field applied to the specimen in order to prevent it from changing its magnetic state. The easiest method is tuming off the objective lens current and focusing with the first intermediate lens. The other method is using a low magnetic-field lens, where the specimen is set above the lens gap.Figure 1 shows an interference micrograph of an isolated particle of barium ferrite on a thin carbon film observed from approximately [111]. A hologram of this particle was recorded by the transmission electron microscope, Hitachi HF-2000, equipped with an electron biprism. The phase distribution of the object electron wave was reconstructed digitally by the Fourier transform method and converted to the interference micrograph Fig 1.

scholarly journals Design of a New 1D Halbach Magnet Array with Good Sinusoidal Magnetic Field by Analyzing the Curved Surface

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2522
Author(s):  
Guangdou Liu ◽  
Shiqin Hou ◽  
Xingping Xu ◽  
Wensheng Xiao
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Permanent Magnets ◽  
Air Gap ◽  
Curved Surface ◽  
Magnetic Flux Density ◽  
Sinusoidal Magnetic Field ◽  
The Magnetic Field

In the linear and planar motors, the 1D Halbach magnet array is extensively used. The sinusoidal property of the magnetic field deteriorates by analyzing the magnetic field at a small air gap. Therefore, a new 1D Halbach magnet array is proposed, in which the permanent magnet with a curved surface is applied. Based on the superposition of principle and Fourier series, the magnetic flux density distribution is derived. The optimized curved surface is obtained and fitted by a polynomial. The sinusoidal magnetic field is verified by comparing it with the magnetic flux density of the finite element model. Through the analysis of different dimensions of the permanent magnet array, the optimization result has good applicability. The force ripple can be significantly reduced by the new magnet array. The effect on the mass and air gap is investigated compared with a conventional magnet array with rectangular permanent magnets. In conclusion, the new magnet array design has the scalability to be extended to various sizes of motor and is especially suitable for small air gap applications.

FINITE ENERGY ONE-HALF MONOPOLE SOLUTIONS

2012 ◽  
Vol 27 (40) ◽  
pp. 1250233 ◽  
Author(s):  
ROSY TEH ◽  
BAN-LOONG NG ◽  
KHAI-MING WONG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Topological Charge ◽  
Magnetic Monopole ◽  
Magnetic Charge ◽  
Finite Energy ◽  
Spatial Infinity ◽  
Yang Mills ◽  
The Magnetic Field

We present finite energy SU(2) Yang–Mills–Higgs particles of one-half topological charge. The magnetic fields of these solutions at spatial infinity correspond to the magnetic field of a positive one-half magnetic monopole at the origin and a semi-infinite Dirac string on one-half of the z-axis carrying a magnetic flux of [Formula: see text] going into the origin. Hence the net magnetic charge is zero. The gauge potentials are singular along one-half of the z-axis, elsewhere they are regular.

Untersuchung des Druckaufbaus einer stationären, magnetfeldstabilisierten Helium-Entladung mit Hilfe magnetischer Messungen

1967 ◽  
Vol 22 (10) ◽  
pp. 1599-1612 ◽  
Author(s):  
Otto Klüber
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Plasma Column ◽  
Ambipolar Diffusion ◽  
Nernst Effect ◽  
Thermomagnetic Effect ◽  
Field Coil ◽  
Neutral Gas ◽  
Ring Currents ◽  
The Magnetic Field

A stationary discharge is produced bya current flowing parallel to the magnetic field ofa cylindrical coil. In the region where the field is homogeneous the pressure in the plasma column is much higher than that in the surrounding neutral gas. This is mainly caused by diamagnetic ring currents, as is shown by measuring the magnetic flux due to these currents. Two effects are primarily responsible for the ring currents in this region: The already known effect of the ambipolar diffusion across the magnetic field anda thermomagnetic effect, called NERNST effect, whose influence on the pressure build-up ofa plasma has not been investigated hitherto. Other phenomena causing ring currents occur in the plasma near the coil ends and outside the field coil.

scholarly journals Properties of the inner penumbral boundary and temporal evolution of a decaying sunspot

2018 ◽  
Vol 620 ◽  
pp. A191 ◽  
Author(s):  
M. Benko ◽  
S. J. González Manrique ◽  
H. Balthasar ◽  
P. Gömöry ◽  
C. Kuckein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Temporal Evolution ◽  
Vertical Component ◽  
Field Vector ◽  
Linear Increase ◽  
Vertical Magnetic Field ◽  
Magnetic Diffusion ◽  
The Magnetic Field ◽  
Linear Decay

Context. It has been empirically determined that the umbra-penumbra boundaries of stable sunspots are characterized by a constant value of the vertical magnetic field. Aims. We analyzed the evolution of the photospheric magnetic field properties of a decaying sunspot belonging to NOAA 11277 between August 28–September 3, 2011. The observations were acquired with the spectropolarimeter on-board of the Hinode satellite. We aim to prove the validity of the constant vertical magnetic-field boundary between the umbra and penumbra in decaying sunspots. Methods. A spectral-line inversion technique was used to infer the magnetic field vector from the full-Stokes profiles. In total, eight maps were inverted and the variation of the magnetic properties in time were quantified using linear or quadratic fits. Results. We find a linear decay of the umbral vertical magnetic field, magnetic flux, and area. The penumbra showed a linear increase of the vertical magnetic field and a sharp decay of the magnetic flux. In addition, the penumbral area quadratically decayed. The vertical component of the magnetic field is weaker on the umbra-penumbra boundary of the studied decaying sunspot compared to stable sunspots. Its value seem to be steadily decreasing during the decay phase. Moreover, at any time of the sunspot decay shown, the inner penumbra boundary does not match with a constant value of the vertical magnetic field, contrary to what is seen in stable sunspots. Conclusions. During the decaying phase of the studied sunspot, the umbra does not have a sufficiently strong vertical component of the magnetic field and is thus unstable and prone to be disintegrated by convection or magnetic diffusion. No constant value of the vertical magnetic field is found for the inner penumbral boundary.

scholarly journals Non-magnetic generating electricity

2021 ◽  
Author(s):  
Shuai Yang
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Electric Field ◽  
Induced Current ◽  
Current Generation ◽  
Scientific Cognition ◽  
The Past ◽  
Directional Movement ◽  
Voltage Generation ◽  
The Magnetic Field

Abstract In the past scientific cognition, changes in the magnetic field produce electric field, so when there is current and voltage generation, need to have a change in magnetic flux, However, in the process of studying the nature of magnetization, we found that the microscopic formation of a magnetic field is the directional movement of positive and negative charges, under the guidance of this theory, we use other methods, realize the separation of positive and negative charges, observation of induced current generation, this can be used as another way to generate electricity.

scholarly journals Photospheric magnetic structure of coronal holes

2019 ◽  
Vol 629 ◽  
pp. A22 ◽  
Author(s):  
Stefan J. Hofmeister ◽  
Dominik Utz ◽  
Stephan G. Heinemann ◽  
Astrid Veronig ◽  
Manuela Temmer
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Coronal Hole ◽  
Magnetic Structure ◽  
Coronal Holes ◽  
Line Of Sight ◽  
Magnetic Elements ◽  
Background Magnetic Field ◽  
The Individual ◽  
The Magnetic Field

In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at ±25 G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc = 0.83 ± 0.01). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of 1.261 ± 0.004 (cc = 0.984 ± 0.001). Relating the magnetic elements to the overall structure of coronal holes, we find that on average (69 ± 8)% of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 h. About (22 ± 4)% of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2−1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc = 0.88 ± 0.02). The remaining flux arises from magnetic elements with lifetimes < 40 h. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc = 0.994 ± 0.001).

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