On the scattering of a metallic cumulative jet with an intense electric current pulse passing through it

The extension of metallic cumulative jets, through which an intense electric current pulse is passed, is numerically simulated in the framework of the model of a uniformly elongating cylindrical rod. Emphasis is on the radial scattering of the jet, which is observed after it escapes from the interelectrode gap. The influence of the magnetic energy accumulated in the jet??s elements under the action of the current is elucidated. For central parts of cumulative jets generated by charges from 50 to 150 mm in diameter, the distributions of the material density and velocity along the radius of the jet immediately after the current cutoff are obtained. These distributions suggest that the surface layer of the jet may separate out and scatter under the action of the current with the central portion of the jet remaining solid. As the current passing through the jet grows, the thickness of its disintegrating layer, which acquires a radial velocity from the axis, increases. Critical currents causing separation of the jet??s surface layer and its collapse are determined.     

Distribution of the magnetic field induced by a current passing through slabs in the superconducting and normal states

The magnetic field induced by a current passing through a long slab is calculated. For the uniformly distributed current, simple formulas for the field components inside and outside the slab are derived. For the nonuniformly distributed current, the magnetic field is numerically calculated for a thin wide superconducting film (the thickness of the film is on the order of the magnetic field penetration depth). It is shown that the current-induced field distribution depends on the form of the exponential dependence of the current density. Experimental distributions are compared with results of a theory where a finite-thickness film is considered as two-dimensional (indefinitely thin). Comparison is also made between experimental and calculated values of the magnetic fields. For a number of points on a plane parallel to the slab and on a plane passing through its center, experimental data are compared with the results obtained by mere summation of partial contributions to the field.     

Displacement current and the generation of parallel electric fields

We show for the first time the dynamical relationship between the generation of magnetic field-aligned electric field (E||) and the temporal changes and spatial gradients of magnetic and velocity shears, and the plasma density in Earth's magnetosphere. We predict that the signatures of reconnection and auroral particle acceleration should have a correlation with low plasma density, and a localized voltage drop (V||) should often be associated with a localized magnetic stress concentration. Previous interpretations of the E|| generation are mostly based on the generalized Ohm's law, causing serious confusion in understanding the nature of reconnection and auroral acceleration.     

On the interfacial capacitance of an electrolyte at a metallic electrode around zero surface charge

The behaviour of the capacitance of a planar double layer containing a restricted primitive model electrolyte (equi-sized rigid ions moving in a continuum dielectric) at and around zero surface charge is examined for a polarizable electrode with particular emphasis on a metallic surface. Capacitance results are reported for symmetric valency (1:1) salts encompassing a range of concentrations and temperatures covering both electrolyte solution and ionic liquid regimes. Although the modified Poisson–Boltzmann theory is principally employed, at higher concentrations the theoretical calculations have been supplemented by Monte Carlo simulations. Capacitance anomaly, that is, increase of capacitance with temperature at low temperatures, is seen to occur when the electrode is an insulator with a low dielectric constant or when it is unpolarized. No capacitance anomaly is, however, seen for a metallic electrode with an infinite dielectric constant and in this situation the capacitance increases (a) dramatically at low temperatures (strong coupling) at a given concentration, and (b) as concentration increases at a given temperature. These capacitance trends are consistent with earlier works in the presence or absence of surface polarization and, in particular, the results for a conducting electrode at ionic liquid concentrations are consistent with that recently reported by Loth et al. [Phys. Rev. E, 82, 056102 (2010)]. Overall the theoretical predictions are qualitative to semi-quantitative with the simulations.     

On generation of boost pairs by a constant electric field

The problem of quantization of a complex scalar field in an external constant uniform electric field is considered in the basis of boost modes. The in- and out-regions in the Minkowski space are deter-mined, and the complete sets of in- and out boost modes describing particles and antiparticles are constructed. The number of boost pairs generated by the field from vacuum in each mode, as well as the total number of produced particles, is calculated.     

Electron energy distribution function in a collisional plasma heated by an electron beam

The electron energy distribution function for the non-resonant electrons in a collisional weakly ionized plasma is found, provided that the intensity of the Langmuir oscillation is spatially dependent. It is assumed that electron-electron collisions are responsible for energy loss.     

Spiral breakup induced by an electric current in a Belousov-Zhabotinsky medium

Sprial breakup in the Belousov-Zhabotinsky reaction has been observed under the influence of an externally applied alternating electric current. The dynamic mechanism of this breakup is explained in the framework of this reaction. The dependence of the critical electric current amplitude on the period of the wave and on the excitability of the medium is analyzed. Spiral breakup is shown to provide a limit of validity of electric-field-induced drift of vortices in excitable media. Experimental results are complemented with numerical simulations provided by two- and three-variable Oregonator models.     

Kerr effect caused by an electric current in a weakly ionized gas

The anisotropy of the velocity distribution caused by an electric current in a fluid leads to a molecular alignment via the non-spherical interaction. This alignment implies a birefringence proportional to the square of the applied electric field just as the ordinary Kerr effect. The kinetic theory of this phenomenon is presented for a lorentzian mixture, viz. a gas of few light charged linear molecules and of many heavy optically isotropic particles. The current-induced contribution to the Kerr effect turns out to be much larger than the contribution which stems from the usually considered orienting influence of the electric field on anisotropic molecules.     

g-factor tuning and manipulation of spins by an electric current

We investigate the Zeeman splitting of the two-dimensional electron gas in an asymmetric silicon quantum well, performing electron-spin-resonance (ESR) experiments. Applying a small dc current we observe a shift in the resonance field due to the additional current-induced Bychkov-Rashba type of spin-orbit field. We also show that a high frequency current may induce electric dipole spin resonance very efficiently. We identify different contributions to this type of ESR signal.     

Evolution of a Harris current sheet in an electric field

Evolution of a Harris current sheet in the presence of an electric field is studied numerically. An explicit scheme is used to recalculate the particle distribution function with respect to velocities. The mechanism of formation of electric fields is analyzed on the basis of the phase volume conservation theorem. The effects of 1D sheet compression and electron and ion acceleration near the magnetic field zero line are described.     

On the effect of a magnetic field on fast charged particles passing through a substance

A transport equation in the small-angle approximation is obtained for a curvilinear beam of fast charged particles passing through a substance in a nonuniform magnetic field. Green functions for this equation are found for an annular beam in a weak-focusing field and for a helical beam in the nonuniform magnetic field.     

Radiative and nonradiative spontaneous decay rates for an electric quadrupole source in the vicinity of a spherical particle

Analytic expressions for the radiative and nonradiative decay rates for an electric quadrupole source (atom, molecule) in the vicinity of a spherical particle (dielectric, metal) have been derived and analyzed within the classical electrodynamics. It has been shown that the highest increase in the decay rates appears in the quasi-static case, when the wavelength of the transition in question is much larger than the characteristic size of the system formed by the particle and the quadrupole. Asymptotic expressions for the decay rates have been derived for this case.     

Microwave generation by a self-sustained current oscillation in an InGaAs/InAlAs superlattice

We observed a self-sustained current oscillation in an InGaAs/InAlAs superlattice at room temperature. The oscillation gave rise to microwave generation at a fundamental frequency around 2 GHz and higher harmonics. The power at the first harmonic was 0.1 mW, corresponding to an efficiency (i.e. ratio of microwave power to dc power) of 3.5%. We attribute the current oscillation to travelling dipole domains.     

Imitation of wave processes by generating an electric explosion of conductors in nonuniformly heated materials

A new method for imitating wave processes in nonuniformly heated materials by means of the electroexplosion of conductors was proposed. The problem of a planar high-current discharge initiated by the explosion of a foil in the air was solved in the 1D approximation of magnetic radiation gas dynamics with regard to the dependence of the conductivity of the foil on the density and temperature of the material during electroexplosion, a dependence that characterizes the specifics of the state of the material in various areas of the phase diagram. The main parameters of the electroexplosion setup were selected. A special construction of the loading unit was developed, which eliminates the effect of current contraction in a planar conductor and ensures a uniform distribution of current over the foil and, consequently, a uniform distribution of the pressure pulse momentum over the surface area of loading. A method for imitating the temperature profile in the sample was proposed. A procedure for measuring the integral pressure pulse momentum under conditions of intense electromagnetic disturbances was developed.     

Transition radiation generated by a particle passing through the apex of a conducting cone

The spatial field distribution is determined for the transition radiation generated by a particle passing through the apex of a cone along its axis. Expressions for the angular distribution of the radiation intensity are obtained for apex angles between 0 and π. Characteristics of transition radiation emitted into a “funnel” and a dihedral angle are compared.     

Nonradiative triplet-singlet transfer of electronic excitation energy between dye molecules in the vicinity of the silver-film surface

Nonradiative triplet-singlet transfer of electronic-excitation energy between molecules of organic dyes (erythrosine and methylene blue) in a polymer film that is deposited on the surface of a silver layer is experimentally studied. It is demonstrated that the energy-transfer efficiency in such a system is lower than the efficiency in the samples without metal layers. The results of the proposed mathematical model are in qualitative agreement with the experimental data.