Ring formation in electromagnetic beams propagating in a magnetoplasma

2009 ◽  
Vol 75 (6) ◽  
pp. 769-785 ◽  
Author(s):  
SHIKHA MISRA ◽  
S. K. MISHRA
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Theoretical Model ◽  
Ring Formation ◽  
Paraxial Approximation ◽  
Electromagnetic Beam ◽  
Self Focusing ◽  
Self Consistent ◽  
Electromagnetic Beams ◽  
The Magnetic Field

AbstractThis paper presents an analysis (in the paraxial approximation) of a self-consistent, steady-state, theoretical model, which explains the ring formation in a Gaussian electromagnetic beam propagating in a magnetoplasma, characterized by ponderomotive and collisional nonlinearities. The condition for the formation of a dark and a bright ring has been derived analytically and the focusing/defocusing of the beam has been investigated in the different regimes. Further, the effect of the magnetic field and the nature of the nonlinearity on the ring formation and self focusing of the beam have also been explored.

Focusing of a dark hollow Gaussian electromagnetic beam in a magnetoplasma

2009 ◽  
Vol 75 (6) ◽  
pp. 731-748 ◽  
Author(s):  
MAHENDRA SINGH SODHA ◽  
S. K. MISHRA ◽  
SHIKHA MISRA
Keyword(s):  
Magnetic Field ◽  
Radial Distance ◽  
The Self ◽  
Electromagnetic Beam ◽  
Dimensionless Radius ◽  
Critical Curves ◽  
Self Focusing ◽  
Subsequent Discussion ◽  
The Magnetic Field

AbstractThis paper presents an analysis and subsequent discussion of the self focusing of a dark hollow Gaussian electromagnetic beam (HGB) in a magnetoplasma, considering ponderomotive and collisional nonlinearities. A paraxial-like approach, in which the relevant parameters are expanded in terms of radial distance from the maximum of the irradiance rather than that from the axis, has been adopted to analyze the propagation of the HGB. The nature of self focusing is highlighted through the critical curves as a plot of dimensionless radius versus power of the beam. The effect of the magnetic field and the nature of the nonlinearity on self focusing of various order HGBs has also been explored.

scholarly journals Simulating Solar Global Magnetism in 3-D

2012 ◽  
Vol 10 (H16) ◽  
pp. 101-103
Author(s):  
A. S. Brun ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Recent Progress ◽  
Convection Zone ◽  
Thermal Structure ◽  
Solar Convection ◽  
Self Consistent ◽  
The Mean ◽  
The Magnetic Field

AbstractWe briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.

scholarly journals Mapping of steady-state electric fields and convective drifts in geomagnetic fields – Part 1: Elementary models

2016 ◽  
Vol 34 (1) ◽  
pp. 55-65 ◽  
Author(s):  
A. D. M. Walker ◽  
G. J. Sofko
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Electric Field ◽  
Electric Fields ◽  
Magnetic Field Line ◽  
Geomagnetic Field ◽  
Geomagnetic Field Models ◽  
Spatial Derivatives ◽  
Field Lines ◽  
The Magnetic Field

Abstract. When studying magnetospheric convection, it is often necessary to map the steady-state electric field, measured at some point on a magnetic field line, to a magnetically conjugate point in the other hemisphere, or the equatorial plane, or at the position of a satellite. Such mapping is relatively easy in a dipole field although the appropriate formulae are not easily accessible. They are derived and reviewed here with some examples. It is not possible to derive such formulae in more realistic geomagnetic field models. A new method is described in this paper for accurate mapping of electric fields along field lines, which can be used for any field model in which the magnetic field and its spatial derivatives can be computed. From the spatial derivatives of the magnetic field three first order differential equations are derived for the components of the normalized element of separation of two closely spaced field lines. These can be integrated along with the magnetic field tracing equations and Faraday's law used to obtain the electric field as a function of distance measured along the magnetic field line. The method is tested in a simple model consisting of a dipole field plus a magnetotail model. The method is shown to be accurate, convenient, and suitable for use with more realistic geomagnetic field models.

scholarly journals Deformation of a magnetic liquid drop in an applied non-stationary uniform magnetic field

2018 ◽  
Vol 185 ◽  
pp. 09006
Author(s):  
Alexander Tyatyushkin
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Steady State ◽  
Uniform Magnetic Field ◽  
Liquid Drop ◽  
Magnetic Liquid ◽  
Stationary Approximation ◽  
The Magnetic Field

Small steady-state deformational oscillations of a drop of magnetic liquid in a nonstationary uniform magnetic field are theoretically investigated. The drop is suspended in another magnetic liquid immiscible with the former. The Reynolds number is so small that the inertia can be neglected. The variation of the magnetic field is so slow that the quasi-stationary approximation for the magnetic field and the quasi-steady approximation for the flow may be used.

Rayleigh–Bénard convection and pattern formation in magnetohydrodynamics

1998 ◽  
Vol 60 (3) ◽  
pp. 529-539 ◽  
Author(s):  
RENU BAJAJ ◽  
S. K. MALIK
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Thermal Instability ◽  
Electrically Conducting ◽  
Electrically Conducting Fluid ◽  
Steady State Bifurcation ◽  
The Stability ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
The Magnetic Field

A nonlinear thermal instability in a layer of electrically conducting fluid in the presence of a magnetic field is discussed. Steady-state bifurcation results in the formation of patterns: rolls, squares and hexagons. The stability of various patterns is also investigated. It is found that in the absence of a magnetic field only rolls are stable, but when the magnetic field strength exceeds a certain finite value, squares and hexagons also become stable.

Dynamically consistent magnetic fields produced by differential rotation

1987 ◽  
Vol 178 ◽  
pp. 521-534 ◽  
Author(s):  
D. R. Fearn ◽  
M. R. E. Proctor
Keyword(s):  
Magnetic Field ◽  
Velocity Field ◽  
Flow Field ◽  
Differential Rotation ◽  
Zonal Flow ◽  
Nonlinear Characteristic ◽  
Poloidal Magnetic Field ◽  
Self Consistent ◽  
Self Consistency ◽  
The Magnetic Field

We investigate the dynamical consequences of an axisymmetric velocity field with a poloidal magnetic field driven by a prescribed e.m.f. E. The problem is motivated by previous investigations of dynamically driven dynamos in the magnetostrophic range. A geostrophic zonal flow field is added to a previously described velocity, and determined by the requirement that Taylor's constraint (Taylor 1963) (guaranteeing dynamical self-consistency of the fields) be satisfied. Several solutions are exhibited, and it is suggested that self-consistent solutions can always be found to this ‘forced’ problem, whereas the usual α-effect dynamo formalism in which E is a linear function of the magnetic field leads to a difficult transcendentally nonlinear characteristic value problem that may not always possess solutions.

The magnetic field profiles of NGC 7331, NGC 2841, and NGC 6946 - A theoretical model

1988 ◽  
Vol 331 ◽  
pp. 116 ◽  
Author(s):  
E. Battaner ◽  
E. Florido ◽  
M. L. Sanchez-Saavedra
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Ngc 6946 ◽  
The Magnetic Field

The Comparison of Magnetic Leakage of Different Teeth Structures in Magnetic Fluid Seal

2011 ◽  
Vol 197-198 ◽  
pp. 314-317 ◽  
Author(s):  
Fei Fei Xing ◽  
De Cai Li ◽  
Wen Ming Yang ◽  
Xiao Long Yang
Keyword(s):  
Magnetic Field ◽  
Finite Element Method ◽  
Finite Element ◽  
Theoretical Model ◽  
Field Distribution ◽  
Magnetic Fluid ◽  
Magnetic Field Distribution ◽  
Two Sides ◽  
The Magnetic Field ◽  
Sealing Gap

Based on the theoretical model, magnetic field distribution of rectangular teeth, two-sides dilated shape and one-side dilated shape teeth structure with common other conditions were calculated using finite element method when the sealing gap was 0.1mm and 0.12mm. The comparison of their results with the same sealing gap showed that rectangular teeth structure had the highest magnetic leakage. Moreover, the magnetic field distribution of sealing structures with rectangular stages on both the shaft and pole pieces under the same design and sealing gap were also calculated using the same method, whose result was compared with rectangular stages on pole pieces only. The comparison showed that the former did not have higher pressure capability obviously but led to higher magnetic leakage.

Focusing of a ring ripple on a Gaussian electromagnetic beam in a magnetoplasma

2009 ◽  
Vol 75 (4) ◽  
pp. 545-561 ◽  
Author(s):  
SHIKHA MISRA ◽  
S. K. MISHRA
Keyword(s):  
Magnetic Field ◽  
Thermal Conduction ◽  
Radial Expansion ◽  
Field Profile ◽  
Electromagnetic Beam ◽  
Critical Curves ◽  
Collisionless Plasmas ◽  
Ponderomotive Nonlinearity ◽  
Electric Field Profile ◽  
The Magnetic Field

AbstractIn this paper we present a theoretical investigation of the growth/propagation of a ring ripple, superposed on a Gaussian electromagnetic beam propagating along the direction of magnetic field in a magnetoplasma. The nature of propagation of the ripple is analysed in a paraxial-like approximation by radial expansion of the dielectric function, corresponding to the composite (Gaussian and ripple) electric field profile of the beam around the position of the maximum of the ripple. The two cases of collisional plasmas (with negligible thermal conduction) and collisionless plasmas (dominant ponderomotive nonlinearity) are considered. The effect of the magnetic field on the critical curves and focusing/defocusing of the ripple are studied and discussed.

scholarly journals A theoretical model of torsional oscillations from a flux transport dynamo model

2010 ◽  
Vol 6 (S273) ◽  
pp. 366-368
Author(s):  
Piyali Chatterjee ◽  
Sagar Chakraborty ◽  
Arnab Rai Choudhuri
Keyword(s):  
Magnetic Field ◽  
Theoretical Model ◽  
Lorentz Force ◽  
High Latitude ◽  
Torsional Oscillation ◽  
Sunspot Cycle ◽  
Dynamo Model ◽  
Flux Transport ◽  
Torsional Oscillations ◽  
The Magnetic Field

AbstractAssuming that the torsional oscillation is driven by the Lorentz force of the magnetic field associated with the sunspot cycle, we use a flux transport dynamo to model it and explain its initiation at a high latitude before the beginning of the sunspot cycle.

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