Dynamics Of Electromagnetic Field Research Articles

Numerical insights into magnetic dynamo action in a turbulent regime

We report on hybrid numerical simulations of a turbulent magnetic dynamo. The simulated set-up mimics the Riga dynamo experiment characterized by Re ≈ 3.5 × 106 and (Gailitis et al 2000 Phys. Rev. Lett. 84 4365–8). The simulations were performed by a simultaneous fully coupled solution of the transient Reynolds-averaged Navier–Stokes (T-RANS) equations for the fluid velocity and turbulence field, and the direct numerical solution (DNS) of the magnetic induction equations. This fully integrated hybrid T-RANS/DNS approach, applied in the finite-volume numerical framework with a multi-block-structured nonorthogonal geometry-fitted computational mesh, reproduced the mechanism of self-generation of a magnetic field in close accordance with the experimental records. In addition to the numerical confirmation of the Riga findings, the numerical simulations provided detailed insights into the temporal and spatial dynamics of flow, turbulence and electromagnetic fields and their reorganization due to mutual interactions, revealing the full four-dimensional picture of a dynamo action in the turbulent regime under realistic working conditions.

Gauge Covariant Formulation of the Wigner Representation through Deformation Quantization: Application to Keldysh Formalism with an Electromagnetic Field

We developed a gauge-covariant formulation of the non-equilibrium Green function method for the dynamical and/or non-uniform electromagnetic field by means of the deformational quantization method. Such a formulation is realized by replacing the Moyal product in the so-called Wigner space by the star product, and facilitates the order-by-order calculation of a gauge-invariant observable in terms of the electromagnetic field. An application of this formalism to the linear response theory is discussed.

Dynamics of electromagnetic field in two-level doped systems

The dynamics of solitons of self-inducted transparency is theoretically and numerically investigated in the case when atoms described in the two-level approximation fit into a medium with ferroelectric properties. The interaction between electromagnetic pulses in the medium and two-level dopant atoms is considered.

Terahertz Frequency Multiplier Operation of Two Dimensional Plasmon Resonant Photomixer

We analytically investigated the feasibility of multiplier operation in the terahertz range for our original plasmon resonant photomixer. The photomixer features two unique structures (doubly interdigitated gate gratings and a vertical cavity) for higher radiation efficiencies. Its total field emission properties are the result of a combination of plasmon excitation dynamics and electromagnetic field dynamics. The plasmon excitation formulated by the hydrodynamic equations exhibits fundamental and harmonic resonances whose intensities monotonically decrease with the number of harmonics due to the dispersive plasma damping factors. The electromagnetic dynamics, on the other hand, formulated by the Maxwell's equations, reflect material- and structure-dependent device parameters; the grating-bi-coupled plasmonic cavity together with the vertical cavity structures produce nonlinear field emission properties. This results in extraordinary field enhancement at distinct frequencies inconsistent with the plasmon resonances. The frequency-dependent FDTD (finite difference time domain method) Maxwell's simulation revealed that the field emission peak frequency shifted upward apart from the fundamental mode of plasmon resonant frequency and approached to its second harmonic frequency with increasing the electron density in the plasmon cavity. Calculated total field emission spectra indicated that highly dense 2D-plasmon conditions enable frequency-doubler operation in the terahertz range.

Liouville and Fokker–Planck dynamics for classical plasmas and radiation

We consider a nonequilibrium statistical system formed by many classical non-relativistic particles of opposite electric charges (plasma) and by the classical dynamical electromagnetic (EM) field. The charges interact with one another directly through instantaneous Coulomb potentials and with the dynamical degrees of freedom of the transverse EM field. The system may also be subject to external influences of: i) either static, but spatially inhomogeneous, electric and magnetic fields (case 1)), or ii) weak distributions of electric charges and currents (case 2)). The particles and the dynamical EM field are described, for any time t > 0, by the classical phase-space probability distribution functional (CPSPDF) f and, at the initial time (t = 0), by the initial CPSPDF fin. The CPSPDF f and fin, multiplied by suitable Hermite polynomials (for particles and field) and integrated over all canonical momenta, yield new moments. The Liouville equation and fin imply a new nonequilibrium linear infinite hierarchy for the moments. In case 1), fin describes local equilibrium but global nonequilibrium, and we propose a long-time approximation in the hierarchy, which introduces irreversibility and relaxation towards global thermal equilibrium. In case 2), the statistical system, having been at global thermal equilibrium, without external influences, for t ≤ 0, is subject to weak external charge-current distributions: then, new hierarchies for moments and their long-time behaviours are discussed in outline. As examples, approximate mean-field (Vlasov) approximations are treated for both cases 1) and 2).

Liouville and Fokker–Planck dynamics for classical plasmas and radiation

AbstractWe consider a nonequilibrium statistical system formed by many classical non‐relativistic particles of opposite electric charges (plasma) and by the classical dynamical electromagnetic (EM) field. The charges interact with one another directly through instantaneous Coulomb potentials and with the dynamical degrees of freedom of the transverse EM field. The system may also be subject to external influences of: i) either static, but spatially inhomogeneous, electric and magnetic fields (case 1)), or ii) weak distributions of electric charges and currents (case 2)). The particles and the dynamical EM field are described, for any time t > 0, by the classical phase‐space probability distribution functional (CPSPDF) f and, at the initial time (t = 0), by the initial CPSPDF fin. The CPSPDF f and fin, multiplied by suitable Hermite polynomials (for particles and field) and integrated over all canonical momenta, yield new moments. The Liouville equation and fin imply a new nonequilibrium linear infinite hierarchy for the moments. In case 1), fin describes local equilibrium but global nonequilibrium, and we propose a long‐time approximation in the hierarchy, which introduces irreversibility and relaxation towards global thermal equilibrium. In case 2), the statistical system, having been at global thermal equilibrium, without external influences, for t ≤ 0, is subject to weak external charge‐current distributions: then, new hierarchies for moments and their long‐time behaviours are discussed in outline. As examples, approximate mean‐field (Vlasov) approximations are treated for both cases 1) and 2).

Surface-plasmon-based electron acceleration

In this paper, we describe a surface-plasmon-based electron acceleration model, the results of which were supported by our recent experimental observations [S. E. Irvine et al., Phys. Rev. Lett. 93, 184801 (2004)]. The model incorporates femtosecond electromagnetic field dynamics and nonlinear electron photoemission characteristics of metallic surfaces. To account for the electromagnetic field structure in space and time, we numerically solve Maxwell's equations in two dimensions. Photoelectron emission is treated quasiclassically in accordance with empirical multiphoton statistics, whereas electron dynamics and energy gain are governed by the Lorentz force. Various aspects of the acceleration mechanism are discussed including surface plasmon coupling and evanescent decay, kinetic energy spectra, angular distributions, angle-resolved energy spectra, and the dependence of maximum energy on the surface electric field.

The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron, the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude, spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS (laser synchrotron source) is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.

Dynamic thermoelectroelastic fields near moving non-smooth interfaces of media

The asymptotic behaviour of dynamic thermal, mechanical and electromagnetic fields near a singular line (a set of corner points) of a moving interface of thermoelectrically conducting media when they are subject to external dynamic thermoelectromechanical actions is established.

Numerical Electromagnetic Field Analysis of Unit Step Response Characteristics of Impulse Voltage Measuring Systems

Unit step response characteristics of impulse voltage measuring systems are studied with the help of numerical electromagnetics code (NEC-2). Prior to this analysis, the accuracy of a transient analysis by this method is investigated for a simple structure. An impulse voltage measuring system, under application of step voltage, behaves like an antenna until a traveling wave makes several roundtrips in its lead wire. NEC-2 code can analyze such dynamic electromagnetic field around a three-dimensional (3-D) conductor system. In the present paper, the role of a shield ring of a divider for lightning impulse voltage is intensively investigated and discussed.

The Kustaanheimo–Stiefel transformation in geometric algebra

The Kustaanheimo-Stiefel (KS) transformation maps the non-linear and singular equations of motion of the three-dimensional Kepler problem to the linear and regular equations of a four-dimensional harmonic oscillator. It is used extensively in studies of the perturbed Kepler problem in celestial mechanics and atomic physics. In contrast to the conventional matrix-based approach, the formulation of the KS transformation in the language of geometric Clifford algebra offers the advantages of a clearer geometrical interpretation and greater computational simplicity. It is demonstrated that the geometric algebra formalism can readily be used to derive a Lagrangian and Hamiltonian description of the KS dynamics in arbitrary static electromagnetic fields. For orbits starting at the Coulomb centre, initial conditions are derived and a framework is set up that allows a discussion of the stability of these orbits.

Radiation reaction for a massless charged particle

We derive effective equations of motion for a massless charged particle coupled to the dynamical electromagnetic field with regard to the radiation back reaction. It is shown that unlike the massive case, not all the divergences resulting from the self-action of the particle are Lagrangian, i.e., can be cancelled out by adding appropriate counterterms to the original action. Besides, the order of renormalized differential equations governing the effective dynamics turns out to be greater than the order of the corresponding Lorentz–Dirac equation for a massive particle. For the case of a homogeneous external field, the first radiative correction to the Lorentz equation is explicitly derived via the reduction of order procedure.

Dynamic Polariton and Quantum State Swapping Betweenan Electromagnetic Field and Atomic Ensemble

We analyse a dynamical swapping of the quantum state in coupled harmonicoscillators. The result can be applied to the interaction of a single-modefield with atomic ensemble in the weak field case. Similar to the caseof electromagnetic induced transparency (EIT), a dynamic polariton isformed. Therefore, the quantum state of the field can be completely mapped on tothe atomic medium, and vice versa. Using this dynamical swapping and theadiabatic transfer in the EIT between the field and atomic ensemble, we propose ascheme in which both the quantum and the coherent information can betransferred from one field to another.

Symplectic areas, quantization, and dynamics in electromagnetic fields

A gauge invariant quantization in a closed integral form is developed over a linear phase space endowed with an inhomogeneous Faraday electromagnetic tensor. An analog of the Groenewold product formula (corresponding to Weyl ordering) is obtained via a membrane magnetic area, and extended to the product of N symbols. The problem of ordering in quantization is related to different configurations of membranes: A choice of configuration determines a phase factor that fixes the ordering and controls a symplectic groupoid structure on the secondary phase space. A gauge invariant solution of the quantum evolution problem for a charged particle in an electromagnetic field is represented in an exact continual form and in the semiclassical approximation via the area of dynamical membranes.

5-2 ガラス製造プロセスにおける流体・電磁場解析の応用可能性について

This paper presents some possibilities for numerical analyses of electro-magnetic field and fluid dynamics to glass making process. The glass making processes consists of melting process, forming process annealing process and post-treatment process. In most of each precess, analyses of electro-magnetic field and fluid dynamics can play important role for designs and operations. For developing new process also, research and application of the analyses are expected

Waves of visual awareness

The old Gestalt idea that perception is driven by the dynamics of electromagnetic fields in the cerebral cortex seems to be alive and well in recent studies of visual awareness, as exemplified by the phenomenon of binocular rivalry. When different images are presented to the two eyes, they are not perceived simultaneously but one image dominates over the other. This dominance not only alternates between the images, but appears to spread in waves (examples of stimuli can be found at http://www.psy.vanderbilt.edu/faculty/blake/rivalry/waves.html). Hugh R. Wilson and colleagues [Nature (2001) 412, 907–910] have recently presented psychophysical evidence that these phenomenal waves are generated by physical waves spreading in primary visual cortex. Wilson et al. trigger waves by abruptly increasing the contrast of one of the images; then, by having subjects indicate the arrival time of the wave at different points, they can measure the speed of propagation. They found that dominance waves travel faster along lines that are collinear than along lines that are merely parallel – echoing the fact that neurons with collinear preferred orientations have stronger excitatory connections, which would be expected to give rise to faster wave propagation. Furthermore, by enlarging the stimuli so that they fall on regions of visual cortex where images are compressed, it is found that speed of propagation depends on cortical distance, rather than on distance in the image. These and other results, confirmed by a simple network model, strongly support the hypothesis that physical waves in visual cortex lead to phenomenal waves of visual awareness. MW

Dynamic analyses of electromagnetic force on ferritic board for AMTEX on JFT-2M

Covering the inside wall of the vacuum vessel with the ferritic boards (FBs) is planned in the third stage of the Advanced Material Tokamak Experiment (AMTEX) on JFT-2M. The total magnetic forces induced on FBs were calculated by the three-dimensional dynamic electromagnetic field analysis code, EMSolution, with solid magnetic elements to consider the coupled effects of eddy current and magnetization, and the skin effect of eddy current. The structural integrity was evaluated on the bolts fixing the FBs to the vacuum vessel.

Cosmological electromagnetic fields due to gravitational wave perturbations

We consider the dynamics of electromagnetic fields in an almost-Friedmann-Robertson-Walker universe using the covariant and gauge-invariant approach of Ellis and Bruni. Focusing on the situation where deviations from the background model are generated by tensor perturbations only, we demonstrate that the coupling between gravitational waves and a weak magnetic test field can generate electromagnetic waves. We show that this coupling leads to an initial pulse of electromagnetic waves whose width and amplitude is determined by the wavelengths of the magnetic field and gravitational waves. A number of implications for cosmology are discussed, in particular we calculate an upper bound of the magnitude of this effect using limits on the quadrapole anisotropy of the Cosmic Microwave Background.

Modeling of the outer electron belt during magnetic storms

The flux dropout of relativistic electrons in the earth’s outer radiation belt, during the main phase of the 26 March 1995 magnetic storm is examined. Outer belt measurements by the Radiation Environment Monitor, REM aboard the STRV-1b satellite are presented to characterize this dropout. In order to simulate the dynamics of the electron belt during the storm main phase a particle tracing code was developed which allows to trace the trajectories of equatorially mirroring electrons in a dynamic magnetospheric electromagnetic field. Two simulations were performed in a non-stationary magnetic field, one taking only the induced electric field into account (fully adiabatic motion), and one with an additional non-stationary convection electric field. The simulations show, that adiabatic deceleration can produce the observed count rate decrease and also the observed inward motion of the count rate peak. The convection electric field causes diffusion, which can take particles from low L values out to the magnetopause and contribute to an additional loss of particles, which is suggested by the observations.

Quantum Kinetic Theory for Laser Plasmas. Dynamical Screening in Strong Fields

AbstractA quantum kinetic theory for correlated charged‐particle systems in strong time‐dependent electromagnetic fields is developed. Our approach is based on a systematic gauge‐invariant nonequilibrium Green's functions formulation. Extending our previous analysis [1] we concentrate on the selfconsistent treatment of dynamical screening and electromagnetic fields which is applicable to arbitrary nonequilibrium situations. The resulting kinetic equation generalizes previous results to quantum plasmas with full dynamical screening and includes many‐body effects. It is, in particular, applicable to the interaction of dense plasmas with strong electromagnetic fields, including laser fields and x‐rays. Furthermore, results for the modification of the plasma screening and the longitudinal field fluctuations due to the electromagnetic field are presented.