On turbulent diffusion of magnetic fields and the loss of magnetic flux from stars

1991 ◽  
Vol 376 ◽  
pp. 199 ◽  
Author(s):  
Samuel I. Vainshtein ◽  
Robert Rosner
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Turbulent Diffusion

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.

Solar Filaments as Tracers of Subsurface Processes

2000 ◽  
Vol 179 ◽  
pp. 177-183
Author(s):  
D. M. Rust
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Coronal Mass Ejections ◽  
Interplanetary Space ◽  
Intermediate Stage ◽  
Coronal Plasma ◽  
Magnetic Helicity ◽  
The Sun ◽  
New Paradigm ◽  
Solar Filaments

AbstractSolar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.

Pinning features of the magnetic flux trapped by YBCO single crystals in weak constant magnetic fields

2013 ◽  
Vol 39 (2) ◽  
pp. 107-110 ◽  
Author(s):  
V. Yu. Monarkha ◽  
V. A. Paschenko ◽  
V. P. Timofeev
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Single Crystals

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.

A Case for Magneto Hydro Dynamics (MHD)

2001 ◽  
Author(s):  
Haim H. Bau
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Lorentz Force ◽  
Electric Fields ◽  
Biological Fluids ◽  
Fluid Volume ◽  
Chaotic Advection ◽  
Complex Flows ◽  
Electric Currents

Abstract In this paper, I review some of our work on the use of magneto hydrodynamics (MHD) for pumping, controlling, and stirring fluids in microdevices. In many applications, one operates with liquids that are at least slightly conductive such as biological fluids. By patterning electrodes inside flow conduits and subjecting these electrodes to potential differences, one can induce electric currents in the liquid. In the presence of a magnetic field, a Lorentz force is generated in a direction that is perpendicular to both the magnetic and electric fields. Since one has a great amount of freedom in patterning the electrodes, one can induce forces in various directions so as to generate complex flows including “guided” flows in virtual, wall-less channels. The magnetic flux generators can be either embedded in the device or be external. Despite their unfavorable scaling (the magnitude of the forces is proportional to the fluid volume), MHD offers many advantages such as the flexibility of applying forces in any desired direction and the ability to adjust the magnitude of the forces by adjusting either the electric and/or magnetic fields. We provide examples of (i) MHD pumps; (ii) controlled networks of conduits in which each conduit is equipped with a MHD actuator and by controlling the voltage applied to each actuator, one can direct the liquid to flow in any desired way without a need for valves; and (iii) MHD stirrers including stirrers that exhibit chaotic advection.

Theoretical Optimization of Cascading Magnets’ Structure for Oxygen Enrichment by Gradient Magnetic Fields

2009 ◽  
Author(s):  
Fengchao Li ◽  
Li Wang ◽  
Ping Wu ◽  
Shiping Zhang
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Oxygen Concentration ◽  
Uniform Magnetic Field ◽  
Oxygen Enrichment ◽  
Gradient Magnetic Field ◽  
Length Direction

Oxygen molecules are paramagnetic while nitrogen molecules are diamagnetic. In the same gradient magnetic field, the magnetizing forces on oxygen molecules are stronger than those on nitrogen molecules, which in opposite directions. The intercepting effect on oxygen molecules by gradient magnetic field can be used for oxygen enrichment from air. The structure, which is called multi-channel cascading magnets array frame in the paper, are optimized by additional yokes. By comparison of distributions of magnetic field in multi-channel array without yokes and that with yokes, the additional yokes can eliminate the differences among different magnetic spaces in multi-channel cascading magnets’ arrays and enhances the magnetic flux densities in spaces. Joining magnets together in the length direction can make the air stay longer in the ‘magnetic sieve’ and raise the oxygen concentration of air flowing out from the optimized multi-channel cascading magnets’ arrays. The inside additional yoke can used to avoid the gradient magnetic field at the joints of the magnets and get near uniform magnetic field along length direction. The optimized multi-channel cascading magnets’ array frames can effectively promote the development of oxygen enrichment from air by “magnetic sieve”.

scholarly journals The Small-Scale Photospheric Magnetic Field as an Indicator of the Dynamo

1993 ◽  
Vol 141 ◽  
pp. 143-146
Author(s):  
K. Petrovay ◽  
G. Szakály
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Observational Data ◽  
Convective Zone ◽  
Small Scale ◽  
Dynamo Theory ◽  
Flux Tubes ◽  
Magnetic Flux Tubes ◽  
Surface Fields

AbstractThe presently widely accepted view that the solar dynamo operates near the base of the convective zone makes it difficult to relate the magnetic fields observed in the solar atmosphere to the fields in the dynamo layer. The large amount of observational data concerning photospheric magnetic fields could in principle be used to impose constraints on dynamo theory, but in order to infer these constraints the above mentioned “missing link” between the dynamo and surface fields should be found. This paper proposes such a link by modeling the passive vertical transport of thin magnetic flux tubes through the convective zone.

scholarly journals Small-Scale Solar Magnetic Fields

1976 ◽  
Vol 71 ◽  
pp. 69-99 ◽  
Author(s):  
J. O. Stenflo
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Solar Surface ◽  
Life Time ◽  
Wave Number ◽  
Small Scale ◽  
Solar Magnetic Fields ◽  
Field Amplification ◽  
Wave Numbers ◽  
Diffuse Form

The observed properties of small-scale solar magnetic fields are reviewed. Most of the magnetic flux in the photosphere is in the form of strong fields of about 100–200 mT (1–2 kG), which have remarkably similar properties regardless of whether they occur in active or quiet regions. These fields are associated with strong atmospheric heating. Flux concentrations decay at a rate of about 107 Wb s-1, independent of the amount of flux in the decaying structure. The decay occurs by smaller flux fragments breaking loose from the larger ones, i.e. a transfer of magnetic flux from smaller to larger Fourier wave numbers, into the wave-number regime where ohmic diffusion becomes significant. This takes place in a time-scale much shorter than the length of the solar cycle.The field amplification occurs mainly below the solar surface, since very little magnetic flux appears in diffuse form in the photosphere, and the life-time of the smallest flux elements is very short. The observations further suggest that most of the magnetic flux in quiet regions is supplied directly from below the solar surface rather than being the result of turbulent diffusion of active-region magnetic fields.

scholarly journals New Infrared Measurements of Magnetic Fields on Cool Stars

1994 ◽  
Vol 154 ◽  
pp. 493-497 ◽  
Author(s):  
Steven H. Saar
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ir Spectra ◽  
Preliminary Analysis ◽  
M Dwarfs ◽  
Pressure Balance ◽  
Infrared Measurements ◽  
Cool Stars ◽  
Rs Cvn Variables ◽  
First Time

I present a preliminary analysis of IR spectra of five K and M dwarfs and two RS CVn variables. Evidence for significant magnetic flux is found on several stars, a number of which are detected for the first time. Field strengths (B) on the RS CVn variables are lower than in the active dwarfs, consistent with the concept of pressure balance limiting B in stellar photospheres. I compare the results with previous measurements.

Cytogenetic effects of 50 Hz magnetic fields of different magnetic flux densities

2000 ◽  
Vol 21 (8) ◽  
pp. 589-596 ◽  
Author(s):  
A. Maes ◽  
M. Collier ◽  
S. Vandoninck ◽  
P. Scarpa ◽  
L. Verschaeve
Keyword(s):  
Magnetic Fields ◽  
Magnetic Flux ◽  
Cytogenetic Effects
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