Quadrupole electromagnetic radiation of an oscillating charged droplet

Analytical calculations using the first order of smallness with respect to dimensionless amplitude of oscillations show that the intensity of electromagnetic radiation of a charged droplet is determined by time-dependent quadrupole moment.     

Capillary oscillations of a charged viscous spheroidal droplet

Dispersion relations are derived for the capillary oscillations of a charged viscous spheroidal droplet by scalarization within perturbation theory using an expansion in two small parameters, viz., the magnitude of the perturbation of the spheroidal surface as a result of thermal fluctuations and the magnitude of the deviation of the equilibrium spheroidal droplet shape from a spherical shape. It is shown analytically that the motion spectrum of the liquid consists of two components that interact in the linear theory: toroidal vortex motion and poloidal potential motions. A numerical analysis reveals that the instability growth rates of the higher modes of a highly charged droplet increase with enhancement of the degree of spheroidal strain and decrease rapidly as the viscosity of the liquid increases. Zh. Tekh. Fiz. 68, 20–27 (April 1998)     

Screened electrostatics of charged particles on a water droplet

We study the electrostatic properties of charged particles trapped at an interface in a water-in-oil microemulsion. The electrostatic potential and the counterion distribution in the water droplet are given in terms of the ratio of the Debye screening length κ^-1 and the droplet radius R. In the limit R→∞ we recover the well-known results for a flat interface. Finite-size corrections are obtained in terms of the small parameter 1/κR. Part of the counterions spread along the interface and form a charged layer of one Debye length thickness. In particular, there is a uniform surface charge contribution. We derive explicit expressions for the electric field, the mobile charge density, and the charge-induced pressure on the interface.     

On acoustic radiation accompanying vibrations of a charged droplet

The dispersion equation relation for the spectrum of capillary oscillations of a charged droplet in a compressible ambient has been derived. It has been shown that such oscillations in the case of droplets, whose sizes and charges are typical of drops in clouds, fogs, or raindrops, cause the generation of sonic and ultrasonic waves in the ambient. An expression for the total intensity of the acoustic radiation generated by a single droplet has been obtained.     

Spectral and scattering theory for a class of strongly oscillating potentials

Following a recent investigation by Pearson [23] on scattering theory for some class of oscillating potentials, we consider the Schrödinger operator inL ²(IR ⁿ ) given by:H =-e ^?U?·e ^2U ?e ^?U +e ^?2U (F + (?·Q)). HereU andF are real functions ofx, andQ is a IR ⁿ -valued function ofx, such that:

1. U is bounded, and the local singularities ofF andQ ² are controlled in a suitable sense by the kinetic energy,
2. U, Q, andF tend to zero at infinity faster than ‖x‖^?1. We defineH by a method of quadratic forms and derive the usual results of scattering theory, namely: the absolutely continuous spectrum is [0, ∞) and the singular continuous spectrum is empty, the wave operators exist and are asymptotically complete. This enlarges the class of already studied strongly oscillating potentials that give rise to the scattering and spectral properties mentioned above.

     

Development paths of the instability of a highly charged viscous droplet

Analysis is presented of the effect on the instability of a droplet of viscous liquid induced by its self-charge of such physical factors as corona discharge initiated in its vicinity and self-sustaining due to photoionization, evaporation of the liquid, and field vaporization of the charge. It has been shown that droplets of micron and submicron size lose their excess charge primarily due to field vaporization.     

Internal bremsstrahlung of strongly interacting charged particles

A universal theoretical model intended for calculating internal-bremsstrahlung spectra is proposed. In this model, which can be applied to describing nuclear decays of various type (such as alpha decay, cluster decay, and proton emission), use is made of realistic nucleus–nucleus potentials. Theoretical internal-bremsstrahlung spectra were obtained for the alpha decay of the ²¹⁴Po nucleus, as well as for the decay of the ²²²Ra nucleus via the emission of a ¹⁴C cluster and for the decay of the ¹¹³Cs nucleus via proton emission, and the properties of these spectra were studied. The contributions of various regions (internal, subbarrier, and external) to the internal-bremsstrahlung amplitude were analyzed in detail. It is shown that the contribution of the internal region to the amplitude for internal bremsstrahlung generated in nuclear decay via proton emission is quite large, but that this is not so for alpha decay and decay via cluster emission. Thus, a process in which strong interaction of nuclear particles affects the internal-bremsstrahlung spectrum if found.     

Electromagnetic energy and momentum from a charged particle

We compute the flux of the stress-energy tensor across a tube surrounding the world line of a charged particle. By slight modifications of the definition of the Coulomb energy-momentum, the resulting expression contains the radiation reaction term (proportional to the square of the four-acceleration) but not the Schott term (proportional to the derivative of the acceleration). The equation of motion for the particle derived from this expression implies a variable rest mass.     

Electromagnetic emission in a magnetized plasma

We present a theory of emission of electromagnetic waves, in the ordinary and extraordinary modes, in the presence of Langmuir turbulence in a magnetized plasma due to a high frequency nonlinear force. The mechanism of emission considered is the plasma-maser interaction which is essentially an energy up-conversion process. The growth rates of the ordinary and extra-ordinary mode emissions are calculated and the results are compared with those obtained from the direct formulation. The scope of application of the results to radio spectra from solar flares is then stressed.M.C. College, India. College of General Education, Kyushu University, Ropponmatsu, Japan. Gauhati University, India. Published in Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 5, pp. 548–562, May, 1994.     

Spray flame dynamics with oscillating flow and droplet grouping

The co-flow laminar spray diffusion flame in an oscillating flow field is investigated. Mild slip is permitted between the droplets and their host surroundings and droplet grouping resulting from the host flow oscillations is accounted for. The spray is modelled using the sectional approach and a perturbation analysis using a small sectional Stokes number is utilised for solving the liquid phase governing equations. The effect of droplet grouping is described through a specially constructed model for the vaporisation Damkohler number. The large chemical Damkohler number assumption is adopted and a formal analytical solution is developed for Schwab-Zeldovitch parameters through which the dynamics of the spray flame front shapes and thermal fields are deduced. Computed results based on the solutions demonstrate how the phenomenon of droplet grouping can lead to the existence of multiple flame sheets as a result of the dynamic change in the type of the main homogeneous flame from under- to over-ventilated as the flow field oscillates. Concomitant fluctuating thermal fields are also shown to be present indicating a potential impact on undesirable pollutants production.     

Electromagnetic perturbations of charged Kerr geometry

The freedom associated with infinitesimal co-ordinate transformations and infinitesimal tetrad rotations within the Newman Penrose formalism is used when considering electromagnetic perturbations of type D geometries. In particular, it is shown that for the charged Kerr geometry, a suitable choice of tetrad rotation leads to equations for the perturbed Newman Penrose components ₀ and ₂ which are closely related to those for the uncharged case.     

General solvation motifs of a charged linear macroion in an aqueous droplet

ABSTRACT

We explore the solvation patterns of a charged rigid and semi-rigid linear macroion in an aqueous droplet. The solvation patterns are summarised in an empirical ‘phase diagram’ on the parameter space defined by the length of the macroion and its charge density. In the study, we employ molecular dynamics and atomistic modelling. The macroion is represented by a positively charged carbon nanotube. Linear macroion-solvent interactions in droplets are distinct from those of spherical ions because of the interplay among several factors such as the tendency of the solvent to form spherical droplets in order to minimise the surface energy, the constraint on the charge of a spherical droplet imposed by the Rayleigh limit, the solvation energy of the macroion and its length. The combination of all these factors may lead to a variety of solvent distributions along the rigid rod such as asymmetric solvation of the linear macroion, formation of spiky ‘star’-like distribution of solvent, partial wetting of the rod by a droplet. The study provides insight into the solvation of macroions in droplets with applications in electrosprayed macroions and atmospheric aerosols. We also propose a possible path of generating a sequence of nanoparticles of different shapes (spheres, multi-point stars) along a linear macromolecule by exploiting the various solvation patterns.     

Electromagnetic radiation of a charged tachyon moving in a dispersive medium

At the present time a number of studies [1–6] have considered the possible properties of ultrarelativistic tachyon particles. In particular, [5, 6] were dedicated to analysis of the radiation of charged tachyons in a vacuum. The goal of the present study is to analyze the radiation emitted by charged tachyons in an immobile dispersive medium. We will consider the following problem: a charged particle moves with velocity v in an immobile dispersive medium and at time t=0 decays to neutral particles and a charged tachyon which moves at a velocity v₀. The tachyon in turn, because of collisions with neutral particles of the medium, at time t= forms a charged particle (electron) also moving with velocity v.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 130–134, June, 1978.In conclusion, the author expresses his sincere thanks to Professor Ya. P. Terletskii for his interest and aid in the study.     

Electromagnetic radiation due to nonlinear oscillations of a charged drop

The nonlinear oscillations of a spherical charged drop are asymptotically analyzed under the conditions of a multimode initial deformation of its equilibrium shape. It is found that if the spectrum of initially excited modes contains two adjacent modes, the translation mode of oscillations is excited among others. In this case, the center of the drop’s charge oscillates about the equilibrium position, generating a dipole electromagnetic radiation. It is shown that the intensity of this radiation is many orders of magnitude higher than the intensity of the drop’s radiation, which arises in calculations of the first order of smallness and is related to the drop’s charged surface oscillations.     

Electromagnetic radiation produced by linear oscillations of a charged drop

A dispersion equation is derived for the capillary oscillations of a charged drop of an ideal incompressible liquid travelling in an ideal incompressible ambient allowing for the energy lost via emission of electromagnetic radiation. The intensity of electromagnetic radiation emitted by a single drop and a storm cloud has been estimated.     

Characterisation of a laser droplet formation process by acoustic emission

The aim of this article is to describe an application of acoustic emission to characterise a process of laser droplet formation from a metal wire. Laser droplet formation is a crucial process in new laser droplet welding technology, where parts are joined by means of the heat content of a liquid metal droplet deposited onto the parts to be joined. A laser beam is used for heating and melting the wire tip, and for detaching the molten pendant droplet. Depending on the process parameters, three different outcomes of the process can be observed: (1) no droplet formed; (2) a droplet formed but not detached; (3) a droplet formed and detached from the wire. It is shown that AE can be used to monitor the process and to indicate the different process outcomes.     

Spontaneous electromagnetic emission from a strongly localized plasma flow

Laboratory observations of electromagnetic ion-cyclotron waves generated by a localized transverse dc electric field are reported. Experiments indicate that these waves result from a strong E×B flow inhomogeneity in a mildly collisional plasma with subcritical magnetic field-aligned current. The wave amplitude scales with the magnitude of the applied radial dc electric field. The electromagnetic signatures become stronger with increasing plasma β, and the radial extent of the power is larger than that of the electrostatic counterpart. Near-Earth space weather implications of the results are discussed.     

Screening of strongly charged macroparticles in liquid electrolyte solutions

A modified Poisson-Boltzmann model has been proposed which makes it possible to describe the screening of strongly charged macroparticles in liquid electrolyte Z: Z solutions in the case when parameter B= ZeQ₀/εRT?1(Q₀ is the surface electric charge, T is the temperature, ε is the solution permittivity, and Z is the valence of ions) provided that the solution is dilute: κR ≡ (8πZ²e²n_i0/εT)^1/2R?1 (n_i0 is the equilibrium number density of ions). It is assumed that the charge Q₀ of a macroparticle appears as a result of adsorption of ions of a certain polarity on its surface. Quantitative criteria of division of dissolved ions into capable and incapable of adsorption are formulated. For aqueous solutions, the adsorption mechanism always leads to values of B ? 1. It is shown that the charge inversion effect predicted by other authors on the basis of different models must be observed for such solutions for all Z ≥ 1. The effect of Brownian movement of macroparticles on their screening is considered. It is shown that viscous forces emerging during such movement lead to peripheral destruction (“washing out”) of the screening ionic shell of macroparticles and, as a result, to violation of their electroneutrality. This results in the emergence of two types of oppositely charged compound particles with small radii close to R and with radii much larger than R, the charge polarity of the latter being opposite to the polarity of Q₀. It is found that both types of ions of compound particles obey the “law of distribution” of the mean energy of their electric field, expressed by formula (29). The problem of ionic screening of gas bubbles accompanied by the formation of bubstons (bubbles stabilized by ions) is considered separately. It is shown that the bubston radius R in pure water and in aqueous solutions of electrolytes is equal to 14 nm irrespective of the ion number density n_i0. The value of n_i0 determines the number density n _b of bubstons themselves, which are formed spontaneously under equilibrium conditions.