Picosecond Studies of Nonequilibrium Flux Dynamics in Superconductors

MRS Proceedings ◽

10.1557/proc-290-323 ◽

1992 ◽

Vol 290 ◽

Author(s):

M. R. Freeman

Keyword(s):

Magnetic Field ◽

Magnetic Flux ◽

Intermediate State ◽

Nonequilibrium State ◽

Normal Metal ◽

Fast Time ◽

Type I ◽

Superconducting Transition ◽

Local Motion ◽

Flux Dynamics

AbstractA fast time-domain magneto-optical technique is used to explore magnetic flux dynamics in the optically driven nonequilibrium state of Type I superconducting Pb films. It is found that the effective penetration of flux through the nonequilibrium intermediate state can be dramatically faster than through the normal metal. The system is probed through the application of rapid transient magnetic field pulses. Above the superconducting transition temperature, a direct measure of the diffusion coefficient of the magnetic field in the normal metal is obtained, on a time scale where the inhomogeneous spatial distribution of scattering sites is relevant. In the nonequilibrium superconductor the observations are dominated by coupling of the field transients to local motion of magnetic flux threading the normal domains. Studies as a function of how far the system is driven from equilibrium, and of the effect of a static applied magnetic field, indicate that the observations reflect the dynamics of normal/superconducting interfaces, and are strongly dependent on the microscopic arrangement of the intermediate state. By contrasting the response of pure Pb films to that of Pb1−xInx alloys, a comparison to Type II superconductivity is made.

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Improvements of Feedback Control Algorism in Two-Dimensional Vector Magnetic Property Measurements

Materials Science Forum ◽

10.4028/www.scientific.net/msf.670.327 ◽

2010 ◽

Vol 670 ◽

pp. 327-335 ◽

Cited By ~ 1

Author(s):

Takashi Todaka ◽

Takeru Sato ◽

Seiji Ishikawa ◽

Yoshitaka Maeda ◽

Masato Enokizono

Keyword(s):

Magnetic Field ◽

Magnetic Property ◽

Feedback Control ◽

Magnetic Flux ◽

High Magnetic Field ◽

Type I ◽

Control Methods ◽

Two Dimensional ◽

Dimensional Vector ◽

Fast Measurement

This paper presents comparison of feedback control algorisms of magnetic flux conditions in two-dimensional vector magnetic property measurements under high magnetic field over 1.6 T. In order to develop a fast measurement algorism, several PID feedback control methods were tested. The results show that the proportion-derivative precedence type (I-PD) control is suitable for reduction of measurement times in vector magnetic property measurements.

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Equilibrium intermediate-state patterns in a type-I superconducting slab in an arbitrarily oriented applied magnetic field

Physical Review B ◽

10.1103/physrevb.88.104504 ◽

2013 ◽

Vol 88 (10) ◽

Cited By ~ 7

Author(s):

John R. Clem ◽

Ruslan Prozorov ◽

Rinke J. Wijngaarden

Keyword(s):

Magnetic Field ◽

Applied Magnetic Field ◽

Intermediate State ◽

Type I

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The Effect of an Applied Transverse Magnetic Field on the Flow Stress of Superconducting Lead

Canadian Journal of Physics ◽

10.1139/p75-119 ◽

1975 ◽

Vol 53 (10) ◽

pp. 945-947 ◽

Cited By ~ 4

Author(s):

T. S. Hutchison ◽

S. L. McBride

Keyword(s):

Magnetic Field ◽

Thermal Conductivity ◽

Flow Stress ◽

Plastic Flow ◽

Transverse Magnetic Field ◽

Intermediate State ◽

Transverse Magnetic ◽

Type I ◽

Field Dependent ◽

Plastic Flow Stress

The intermediate state in type I superconductors of rod form subject to a transverse magnetic field is characterized by a laminar normal superconducting structure. This gives rise to temperature and field dependent minima in the thermal conductivity. The measured plastic flow stress of lead crystals under these conditions is shown to be field dependent and to be related to the thermal conductivity via the previously developed relation (σH − σS) = −AT ln (κH/κS).

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Magnetic flux density and the critical field in the intermediate state of type-I superconductors

Physical Review B ◽

10.1103/physrevb.89.100503 ◽

2014 ◽

Vol 89 (10) ◽

Cited By ~ 8

Author(s):

V. Kozhevnikov ◽

R. J. Wijngaarden ◽

J. de Wit ◽

C. Van Haesendonck

Keyword(s):

Magnetic Flux ◽

Flux Density ◽

Critical Field ◽

Intermediate State ◽

Magnetic Flux Density ◽

Type I

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Experimental Study of the Magnetic Field Distribution and Shape of Domains Near the Surface of a Type-I Superconductor in the Intermediate State

Journal of Superconductivity and Novel Magnetism ◽

10.1007/s10948-020-05576-1 ◽

2020 ◽

Vol 33 (11) ◽

pp. 3361-3376

Author(s):

V. Kozhevnikov ◽

A. Suter ◽

T. Prokscha ◽

C. Van Haesendonck

Keyword(s):

Magnetic Field ◽

Experimental Study ◽

Field Distribution ◽

Intermediate State ◽

Magnetic Field Distribution ◽

Type I ◽

The Magnetic Field

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Impeded Growth of Magnetic Flux Bubbles in the Intermediate State Pattern of Type I Superconductors

Physical Review Letters ◽

10.1103/physrevlett.92.147001 ◽

2004 ◽

Vol 92 (14) ◽

Cited By ~ 19

Author(s):

V. Jeudy ◽

C. Gourdon ◽

T. Okada

Keyword(s):

Magnetic Flux ◽

Intermediate State ◽

Type I

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Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

International Astronomical Union Colloquium ◽

10.1017/s0252921100064630 ◽

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.

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Basic Statements of Research and Magnetic Field of Axial Excitation Inductor Generator

Scientific Journal of Riga Technical University Power and Electrical Engineering ◽

10.2478/v10144-011-0008-8 ◽

2011 ◽

Vol 28 (1) ◽

pp. 49-52

Author(s):

Igors Stroganovs ◽

Andrejs Zviedris

Keyword(s):

Magnetic Field ◽

Finite Element Method ◽

Finite Element ◽

Magnetic Flux ◽

Magnetic System ◽

System Optimization ◽

Magnetic Saturation ◽

The Finite Element Method ◽

Flux Linkage ◽

Axial Excitation

Basic Statements of Research and Magnetic Field of Axial Excitation Inductor GeneratorIn this work the main features of axial excitation inductor generators are described. Mathematical simulation of a magnetic field is realized by using the finite element method. The objective of this work is to elucidate how single elements shape, geometric dimensions and magnetic saturation of magnetic system affect the main characteristics of the field (magnetic induction, magnetic flux linkage). The main directions of a magnetic system optimization are specified.

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Energetics of magnetic transients in a solar active region plage

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834548 ◽

2019 ◽

Vol 623 ◽

pp. A176 ◽

Cited By ~ 3

Author(s):

L. P. Chitta ◽

A. R. C. Sukarmadji ◽

L. Rouppe van der Voort ◽

H. Peter

Keyword(s):

Magnetic Field ◽

Active Region ◽

Magnetic Flux ◽

Numerical Simulations ◽

Extreme Ultraviolet ◽

Spatial Scales ◽

Coronal Loops ◽

The Sun ◽

Flux Emergence ◽

Transient Events

Context. Densely packed coronal loops are rooted in photospheric plages in the vicinity of active regions on the Sun. The photospheric magnetic features underlying these plage areas are patches of mostly unidirectional magnetic field extending several arcsec on the solar surface. Aims. We aim to explore the transient nature of the magnetic field, its mixed-polarity characteristics, and the associated energetics in the active region plage using high spatial resolution observations and numerical simulations. Methods. We used photospheric Fe I 6173 Å spectropolarimetric observations of a decaying active region obtained from the Swedish 1-m Solar Telescope (SST). These data were inverted to retrieve the photospheric magnetic field underlying the plage as identified in the extreme-ultraviolet emission maps obtained from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). To obtain better insight into the evolution of extended unidirectional magnetic field patches on the Sun, we performed 3D radiation magnetohydrodynamic simulations of magnetoconvection using the MURaM code. Results. The observations show transient magnetic flux emergence and cancellation events within the extended predominantly unipolar patch on timescales of a few 100 s and on spatial scales comparable to granules. These transient events occur at the footpoints of active region plage loops. In one case the coronal response at the footpoints of these loops is clearly associated with the underlying transient. The numerical simulations also reveal similar magnetic flux emergence and cancellation events that extend to even smaller spatial and temporal scales. Individual simulated transient events transfer an energy flux in excess of 1 MW m−2 through the photosphere. Conclusions. We suggest that the magnetic transients could play an important role in the energetics of active region plage. Both in observations and simulations, the opposite-polarity magnetic field brought up by transient flux emergence cancels with the surrounding plage field. Magnetic reconnection associated with such transient events likely conduits magnetic energy to power the overlying chromosphere and coronal loops.

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