Magnetic-field generation in laser fusion and hot-electron transport

1986 ◽  
Vol 64 (8) ◽  
pp. 912-919 ◽  
Author(s):  
M. G. Haines
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Diffusion Processes ◽  
Anisotropic Pressure ◽  
Laser Fusion ◽  
Hot Electron ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
The Many ◽  
Many Sources

The many sources of generation of magnetic field are derived from a generalized Ohm's law. These sources include the [Formula: see text] effect, anisotropic pressure, as well as the effect of the quiver velocity associated with the incident laser beam. The magnetic field can be generated either through some imposed lack of spherical symmetry or through an instability. Among the latter, the collisional Weibel instability appears to be the most important. Convection and amplification can occur through the Nernst effect, and the resulting magnetic-field structure can inhibit fast-electron transport. Dynamo action and diffusion processes are also included in this review.

scholarly journals XIII.—The Strains Produced in Iron, Steel, and Nickel Tubes in the Magnetic Field. Part I.

1897 ◽  
Vol 38 (3) ◽  
pp. 527-555 ◽  
Author(s):  
C. G. Knott
Keyword(s):  
Magnetic Field ◽  
Short Note ◽  
Interesting Phenomenon ◽  
Senior Student ◽  
Sources Of Error ◽  
Physical Laboratory ◽  
The Many ◽  
Many Sources ◽  
The Magnetic Field ◽  
Interior Volume

On July 20th, 1891, I communicated to the Society a short note on the effect of longitudinal magnetisation on the interior volume of iron and nickel tubes (see Proceedings, 1890–91, pp. 315–7). These earliest results of observation of a new and interesting phenomenon in magnetic strains were obtained during my last few months' residence in Japan. In following out the lines of research therein suggested, I have been fortunate in having had placed at my disposal by Professor Tait the resources of the Physical Laboratory of Edinburgh University. I desire here to record my great indebtedness to him for the interest he has taken in the work, and for his many helpful suggestions. In surmounting the many experimental difficulties met with at every turn, I had the invaluable co-operation of Mr A. Shand, a senior student in the Physical Laboratory. Various results obtained since 1892 have been communicated in short notes from time to time (see Proceedings, 1891–2, pp. 85–88, 249–252; 1893–4, pp. 295–7; 1894–5, pp. 334–5; see also B. A. Reports, 1892 and 1893); but it was not possible to regard these as altogether satisfactory. It was only in May of last year (1895) that the many sources of error were finally got rid of, and the apparatus perfected. The present paper deals entirely with the results obtained since then. In these later experiments I was ably assisted by Mr A. C. Smith, a student in the Physical Laboratory.

Magnetic field generation by baroclinic waves

1975 ◽  
Vol 347 (1648) ◽  
pp. 125-140 ◽  
Keyword(s):  
Magnetic Field ◽  
Plane Layer ◽  
Rotating Magnetic Field ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
Wind Speeds ◽  
Baroclinic Waves ◽  
The Face ◽  
Layer I ◽  
Horizontal Density Gradient

The general theory of the linear instabilities created by density differences in a rotating magnetic system is considered, and is applied to a plane layer stably stratified but with a slight superimposed horizontal density gradient that can give rise to baroclinic waves, modified by the presence of a horizontal co-rotating magnetic field parallel to the thermal wind. It is shown that, unlike the conceptually similar models of Gilman, regeneration of this magnetic field by the waves in the face of a slight resistivity of the medium can only occur within the critical layer, i. e. the diffusive layer surrounding the level at which wave and wind speeds are equal. Conditions for such self-sustaining dynamo action are given.

scholarly journals Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow

2013 ◽  
Vol 731 ◽  
pp. 1-45 ◽  
Author(s):  
A. Riols ◽  
F. Rincon ◽  
C. Cossu ◽  
G. Lesur ◽  
P.-Y. Longaretti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shear Flow ◽  
Shear Flows ◽  
Three Dimensional ◽  
Transition To Turbulence ◽  
Global Bifurcations ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
Systems Research ◽  
Hydrodynamic Shear

AbstractMagnetorotational dynamo action in Keplerian shear flow is a three-dimensional nonlinear magnetohydrodynamic process, the study of which is relevant to the understanding of accretion processes and magnetic field generation in astrophysics. Transition to this form of dynamo action is subcritical and shares many characteristics with transition to turbulence in non-rotating hydrodynamic shear flows. This suggests that these different fluid systems become active through similar generic bifurcation mechanisms, which in both cases have eluded detailed understanding so far. In this paper, we build on recent work on the two problems to investigate numerically the bifurcation mechanisms at work in the incompressible Keplerian magnetorotational dynamo problem in the shearing box framework. Using numerical techniques imported from dynamical systems research, we show that the onset of chaotic dynamo action at magnetic Prandtl numbers larger than unity is primarily associated with global homoclinic and heteroclinic bifurcations of nonlinear magnetorotational dynamo cycles born out of saddle-node bifurcations. These global bifurcations are found to be supplemented by local bifurcations of cycles marking the beginning of period-doubling cascades. The results suggest that nonlinear magnetorotational dynamo cycles provide the pathway to injection of both kinetic and magnetic energy for the problem of transition to turbulence and dynamo action in incompressible magnetohydrodynamic Keplerian shear flow in the absence of an externally imposed magnetic field. Studying the nonlinear physics and bifurcations of these cycles in different regimes and configurations may subsequently help to understand better the physical conditions of excitation of magnetohydrodynamic turbulence and instability-driven dynamos in a variety of astrophysical systems and laboratory experiments. The detailed characterization of global bifurcations provided for this three-dimensional subcritical fluid dynamics problem may also prove useful for the problem of transition to turbulence in hydrodynamic shear flows.

scholarly journals The effect of velocity shear on dynamo action due to rotating convection

2013 ◽  
Vol 717 ◽  
pp. 395-416 ◽  
Author(s):  
D. W. Hughes ◽  
M. R. E. Proctor
Keyword(s):  
Magnetic Field ◽  
Velocity Field ◽  
Large Scale ◽  
Mean Field ◽  
Magnetic Reynolds Number ◽  
Velocity Shear ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
Rotating Convection ◽  
The Magnetic Field

AbstractRecent numerical simulations of dynamo action resulting from rotating convection have revealed some serious problems in applying the standard picture of mean field electrodynamics at high values of the magnetic Reynolds number, and have thereby underlined the difficulties in large-scale magnetic field generation in this regime. Here we consider kinematic dynamo processes in a rotating convective layer of Boussinesq fluid with the additional influence of a large-scale horizontal velocity shear. Incorporating the shear flow enhances the dynamo growth rate and also leads to the generation of significant magnetic fields on large scales. By the technique of spectral filtering, we analyse the modes in the velocity that are principally responsible for dynamo action, and show that the magnetic field resulting from the full flow relies crucially on a range of scales in the velocity field. Filtering the flow to provide a true separation of scales between the shear and the convective flow also leads to dynamo action; however, the magnetic field in this case has a very different structure from that generated by the full velocity field. We also show that the nature of the dynamo action is broadly similar irrespective of whether the flow in the absence of shear can support dynamo action.

Characterization of GaAs/AlGaAs hot electron transistors using magnetic field effects on launched-electron transport

1986 ◽  
Vol 174 (1-3) ◽  
pp. 481-486 ◽  
Author(s):  
K. Imamura ◽  
S. Muto ◽  
N. Yokoyama ◽  
M. Sasa ◽  
H. Ohnishi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Hot Electron ◽  
Magnetic Field Effects ◽  
Field Effects ◽  
Electron Transistors

Hot‐electron transport in GaAs in the presence of a magnetic field

1987 ◽  
Vol 51 (18) ◽  
pp. 1425-1427 ◽  
Author(s):  
P. H. Beton ◽  
A. P. Long ◽  
M. J. Kelly
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Hot Electron ◽  
Hot Electron Transport

Magnetic field dependence of hot‐electron transport in GaAs

1985 ◽  
Vol 47 (9) ◽  
pp. 964-966 ◽  
Author(s):  
J. R. Hayes ◽  
A. F. J. Levi ◽  
W. Wiegmann
Keyword(s):  
Magnetic Field ◽  
Electron Transport ◽  
Field Dependence ◽  
Magnetic Field Dependence ◽  
Hot Electron ◽  
Hot Electron Transport

scholarly journals Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars

2018 ◽  
Vol 609 ◽  
pp. A51 ◽  
Author(s):  
J. Warnecke ◽  
M. Rheinhardt ◽  
S. Tuomisto ◽  
P. J. Käpylä ◽  
M. J. Käpylä ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Turbulent Transport ◽  
Transport Coefficients ◽  
Test Field ◽  
Nonlinear Feedback ◽  
Magnetic Field Generation ◽  
Dynamo Action ◽  
Flux Transport ◽  
The Magnetic Field

Aims.We investigate dynamo action in global compressible solar-like convective dynamos in the framework of mean-field theory.Methods.We simulate a solar-type star in a wedge-shaped spherical shell, where the interplay between convection and rotation self-consistently drives a large-scale dynamo. To analyze the dynamo mechanism we apply the test-field method for azimuthally (φ) averaged fields to determine the 27 turbulent transport coefficients of the electromotive force, of which six are related to theαtensor. This method has previously been used either in simulations in Cartesian coordinates or in the geodynamo context and is applied here for the first time to fully compressible simulations of solar-like dynamos.Results.We find that theφφ-component of theαtensor does not follow the profile expected from that of kinetic helicity. The turbulent pumping velocities significantly alter the effective mean flows acting on the magnetic field and therefore challenge the flux transport dynamo concept. All coefficients are significantly affected by dynamically important magnetic fields. Quenching as well as enhancement are being observed. This leads to a modulation of the coefficients with the activity cycle. The temporal variations are found to be comparable to the time-averaged values and seem to be responsible for a nonlinear feedback on the magnetic field generation. Furthermore, we quantify the validity of the Parker-Yoshimura rule for the equatorward propagation of the mean magnetic field in the present case.

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