scholarly journals Dynamic Time Dependent Hexagonal Magnetoconvection

1985 ◽  
Vol 38 (6) ◽  
pp. 885 ◽  
Author(s):  
JM Lopez ◽  
JO Murphy
Keyword(s):  
Magnetic Field ◽  
Rayleigh Number ◽  
Time Dependence ◽  
Single Mode ◽  
Time Dependent ◽  
Oscillatory Solutions ◽  
Field Amplification ◽  
Nonzero Mean ◽  
Dynamic Time ◽  
Parameter Ranges

The time dependence of the single mode hexagonal magnetoconvective system has been investigated numerically at high Rayleigh number. It is established that, in certain parameter ranges, the system has oscillatory solutions which not only have a periodic nature, but also develop into chaotic and intermittent solutions. Further, the system generates nonzero mean kinetic and magnetic helicity together with substantial magnetic field amplification. These features are shown to be maintained in time without any externally imposed rotation of the system.

scholarly journals Nonlinear Bifurcations to Time-dependent Rayleigh?Benard Convection

1988 ◽  
Vol 41 (1) ◽  
pp. 63
Author(s):  
JM Lopez ◽  
JO Murphy
Keyword(s):  
Vertical Component ◽  
Single Mode ◽  
Time Dependent ◽  
Convection Cell ◽  
Initial Growth ◽  
Periodic Behaviour ◽  
Parameter Ranges ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard ◽  
Dependent Behaviour

The single-mode equations of Boussinesq thermal convection have been extended to include a toroidal component of velocity and hence the associated vertical component of vorticity. This formulation allows, under certain determined conditions, the purely poloidal solutions to become unstable to toroidal perturbations via symmetry breaking bifurcations. The bifurcation sequences are governed by a three parameter family: the aspect ratio of the convection cell, the Prandtl number of the fluid and the Rayleigh number of the flow. The initial growth of the vertical vorticity has been found always to be steady. However, in certain parameter ranges there are transitions leading to time-dependent behaviour via a Hopf bifurcation which may be in the form of symmetrical oscillations, asymmetrical oscillations, doubly-periodic behaviour or, possibly, chaos, depending on the form of the transient poloidal phase of the evolution.

TIME DEPENDENCE OF RESISTIVE TRANSITION OF EPITAXIAL GdBa2Cu3Oy SUPERCONDUCTING FILM IN PULSED MAGNETIC FIELD

1992 ◽  
Vol 06 (23) ◽  
pp. 1475-1479
Author(s):  
LI XIAO-GUANG ◽  
LI HONGCHENG ◽  
ZHANG YUHENG
Keyword(s):  
Magnetic Field ◽  
Time Dependence ◽  
Time Dependent ◽  
Pulsed Magnetic Field ◽  
Superconducting Film ◽  
Superconducting Transition ◽  
Resistive Transition ◽  
Field Technique ◽  
Flux Motion

Broadening of resistive superconducting transition in an epitaxial GdBa2Cu3Oy, superconducting film below Tc was studied by the pulsed magnetic field technique. The results show that the transition in the field is not only broadened but also time-dependent. It is suggested that the time dependence of the broadening of resistive transition is mainly caused by flux motion.

scholarly journals Moving Pearl Vortices in Thin-Film Superconductors

2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Vladimir Kogan ◽  
Norio Nakagawa
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Time Dependent ◽  
Superconducting Thin Film ◽  
Self Energy ◽  
London Equation ◽  
The Magnetic Field

The magnetic field hz of a moving Pearl vortex in a superconducting thin-film in (x,y) plane is studied with the help of the time-dependent London equation. It is found that for a vortex at the origin moving in +x direction, hz(x,y) is suppressed in front of the vortex, x>0, and enhanced behind (x<0). The distribution asymmetry is proportional to the velocity and to the conductivity of normal quasiparticles. The vortex self-energy and the interaction of two moving vortices are evaluated.

scholarly journals Hamiltonian Approach to Magnetic Fields with Toroidal Surfaces

1985 ◽  
Vol 40 (10) ◽  
pp. 959-967
Author(s):  
A. Salat
Keyword(s):  
Magnetic Field ◽  
Hamiltonian System ◽  
Magnetic Fields ◽  
Constant Pressure ◽  
Time Dependent ◽  
Hamiltonian Approach ◽  
One Dimensional ◽  
Mhd Equilibrium ◽  
Magnetic Surfaces ◽  
Rotational Transform

The equivalence of magnetic field line equations to a one-dimensional time-dependent Hamiltonian system is used to construct magnetic fields with arbitrary toroidal magnetic surfaces I = const. For this purpose Hamiltonians H which together with their invariants satisfy periodicity constraints have to be known. The choice of H fixes the rotational transform η(I). Arbitrary axisymmetric fields, and nonaxisymmetric fields with constant η(I) are considered in detail.Configurations with coinciding magnetic and current density surfaces are obtained. The approach used is not well suited, however, to satisfying the additional MHD equilibrium condition of constant pressure on magnetic surfaces.

scholarly journals Measurements of the time-dependent cosmic-ray Sun shadow with seven years of IceCube data: Comparison with the Solar cycle and magnetic field models

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
M. G. Aartsen ◽  
R. Abbasi ◽  
M. Ackermann ◽  
J. Adams ◽  
J. A. Aguilar ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Cosmic Ray ◽  
Time Dependent ◽  
Data Comparison

scholarly journals Structure evolution of suspensions under time-dependent electric or magnetic field

2021 ◽  
Author(s):  
Konstantinos Manikas ◽  
Markus Hütter ◽  
Patrick D. Anderson
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Brownian Dynamics ◽  
Thermal Fluctuations ◽  
Time Dependent ◽  
Structure Evolution ◽  
Strength Increase ◽  
Large Rotation ◽  
Dynamics Simulations ◽  
Brownian Dynamics Simulations

AbstractThe effect of time-dependent external fields on the structures formed by particles with induced dipoles dispersed in a viscous fluid is investigated by means of Brownian Dynamics simulations. The physical effects accounted for are thermal fluctuations, dipole-dipole and excluded volume interactions. The emerging structures are characterised in terms of particle clusters (orientation, size, anisotropy and percolation) and network structure. The strength of the external field is increased in one direction and then kept constant for a certain amount of time, with the structure formation being influenced by the slope of the field-strength increase. This effect can be partially rationalized by inhomogeneous time re-scaling with respect to the field strength, however, the presence of thermal fluctuations makes the scaling at low field strength inappropriate. After the re-scaling, one can observe that the lower the slope of the field increase, the more network-like and the thicker the structure is. In the second part of the study the field is also rotated instantaneously by a certain angle, and the effect of this transition on the structure is studied. For small rotation angles ($$\theta \le 20^{{\circ }}$$ θ ≤ 20 ∘ ) the clusters rotate but stay largely intact, while for large rotation angles ($$\theta \ge 80^{{\circ }}$$ θ ≥ 80 ∘ ) the structure disintegrates and then reforms, due to the nature of the interactions (parallel dipoles with perpendicular inter-particle vector repel each other). For intermediate angles ($$20<\theta <80^{{\circ }}$$ 20 < θ < 80 ∘ ), it seems that, during rotation, the structure is altered towards a more network-like state, as a result of cluster fusion (larger clusters). The details provided in this paper concern an electric field, however, all results can be projected into the case of a magnetic field and paramagnetic particles.

scholarly journals Magnetic field amplification in newly-born neutron stars

1996 ◽  
Vol 160 ◽  
pp. 435-436
Author(s):  
H.-J. Wiebicke ◽  
U. Geppert
Keyword(s):  
Magnetic Field ◽  
Neutron Stars ◽  
Gravitational Collapse ◽  
Dipole Field ◽  
Numerical Calculations ◽  
Selection Effects ◽  
Thermoelectric Effects ◽  
Field Amplification ◽  
Seed Field ◽  
Flux Conservation

AbstractWe present a scenario of magnetic field (MF) evolution of newly-born neutron stars (NSs). Numerical calculations show that in the hot phase of young NSs the MF can be amplified by thermoelectric effects, starting from a moderately strong seed-field. Therefore, there is no need to assume a 1012G dipole field immediately after the gravitational collapse of the supernova (SN) event. The widely accepted scenario for such a field to be produced by flux conservation during the collapse is critically discussed. Instead, it can be generated by amplification and selection effects in the first 104yrs, and by the subsequent fast ohmic decay of higher multipole components, when the NS cools down.

OBSERVATION OF THE TRANSVERSE STERN–GERLACH EFFECT IN NEUTRAL POTASSIUM

1967 ◽  
Vol 45 (4) ◽  
pp. 1481-1495 ◽  
Author(s):  
Myer Bloom ◽  
Eric Enga ◽  
Hin Lew
Keyword(s):  
Magnetic Field ◽  
Angular Velocity ◽  
Reference Frame ◽  
Inhomogeneous Magnetic Field ◽  
Time Dependent ◽  
Effective Magnetic Field ◽  
Classical Analysis ◽  
At Resonance ◽  
Rotating Reference Frame

A successful transverse Stern–Gerlach experiment has been performed, using a beam of neutral potassium atoms and an inhomogeneous time-dependent magnetic field of the form[Formula: see text]A classical analysis of the Stern–Gerlach experiment is given for a rotating inhomogeneous magnetic field. In general, when space quantization is achieved, the spins are quantized along the effective magnetic field in the reference frame rotating with angular velocity ω about the z axis. For ω = 0, the direction of quantization is the z axis (conventional Stern–Gerlach experiment), while at resonance (ω = −γH0) the direction of quantization is the x axis in the rotating reference frame (transverse Stern–Gerlach experiment). The experiment, which was performed at 7.2 Mc, is described in detail.

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