Scattering of a plane inhomogeneous electromagnetic wave by a spherical particle

We extend an analytical solution for the problem of diffraction of a plane wave by a spherical particle to the case of an inhomogeneous wave. Numerical examples showing a significant change in the scattered-wave structure compared with the case of diffraction of a homogeneous wave are presented. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 1, pp. 72–81, January 2006.     

Absorption of electromagnetic radiation by an inhomogeneous spherical particle

The cross section of absorption of electromagnetic radiation by an inhomogeneous spherical particle is calculated. The general case of an arbitrary value of the ratio of the particle radius to the radius of the dielectric core is considered. The condition of diffuse reflection of electrons from the inner and outer surfaces of the metal layer of the particle is taken as the boundary condition of the problem. The limiting cases are considered and the results obtained are discussed.     

Light scattering by an inhomogeneous spherical particle with intermediate layers

A model of a radially inhomogeneous multilayer spherical particle with a continuously varying refractive index in the intermediate layers between the shells of the particle and between the particle and the surroundings is proposed. Such a particle scatters light much like a dust particle with a rough and ragged surface of the layers, which is simulated with the help of the discrete dipole approximation method. For dust particles whose surface shape deviates from the spherical one, the refractive index profile and the behavior of the extinction Q _ext(x) and absorption Q _abs(x) efficiency factors with increasing thickness of the intermediate layers are studied. Properties of such particles in dependence on the number of layers are also studied. It is revealed that, as the number of shells increases, the order of the relative position of substances ceases to play a role, as is also the case for a multilayer spherical particle without intermediate layers. It is shown that, upon an increase in the number of shells at the same percentages of substances in the intermediate layers, the difference of the values of Q _ext(x) and Q _abs(x) from the corresponding values calculated with the model without intermediate layers decreases.     

Depolarization of the electromagnetic field in a locally inhomogeneous earth-ionosphere waveguide

This paper presents a further development of the numerical-analytical method for the solution of three-dimensional problems in the theory of radio wave propagation. We consider a vector problem of the electromagnetic field of a vertical electric dipole in a plane Earth-ionosphere waveguide with a local large-scale irregularity on the anisotropic ionosphere wall. The possibility of lowering (elevating) of the local region of the upper waveguide wall with respect to the regular ionosphere level is taken into account. The field components on the boundary surfaces obey the Leontovich impedance conditions. The problem is reduced to a system of two-dimensional integral equations taking into account the overexcitation and depolarization of the field scattered by the irregularity. Using asymptotic (with respect to the parameter kr ≫1) integration along the direction perpendicular to the ray path, we transform this system to a system of one-dimensional integral equations. The system is solved numerically in the diagonal approximation, combining direct inversion of the Volterra integral operator and the subsequent iterations. The proposed method reduces the computer time required for solving the problem and is useful for the study of both small-scale and large-scale irregularities. We obtained estimates of the TE field components that are not excited by the source considered and originate entirely from field scattering by a three-dimensional irregularity disturbing the geometric regularity of the ionospheric waveguide wall. State University of St. Petersburg, Russia Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 7, pp. 617–629, July, 2000.     

On rainbows of inhomogeneous spherical droplets

The paper is devoted to the study of the intensity distributions and the angular spectra of the second and fifth rainbows of homogeneous and inhomogeneous spherical particles predicted by Lorenz-Mie theory. The results show that the distribution around the second rainbow angle for a homogeneous sphere of refractive index between 1.32 and 1.33 is due to the interference of the light after two or five internal reflections. The structure of the scattering diagram and the angular spectrum for homogeneous and radially inhomogeneous spheres are studied. For a homogeneous sphere we show that the second and fifth rainbows can be independently reconstructed by filtering the calculated spectrum. Since each order of rainbow penetrates the particle to different depths, such methods could be used to provide information about the refractive index profile or the temperature gradient of an inhomogeneous sphere. The Airy-like peaks of the second and fifth rainbows are closely connected with the refractive index profile, which is beneficial to the measurement of its refractive index profile or temperature gradient.     

Canonical form of the averaged equations of motion of a charged particle upon superposition of an electromagnetic wave field on a weakly inhomogeneous magnetic field

The Hamiltonian function of a charged particle in a weakly inhomogeneous magnetic field perturbed by a plane wave is determined correct to terms of the order of the small parameter inclusive. The canonical motion equations averaged over the fast phase for motion in the vicinity of the resonance are derived.     

The electromagnetic field above a two-dimensional inhomogeneous structure. Boundary conditions

Summary The induction problem in the case of an inhomogeneous two-dimensional conductor presenting a vertical contact between two media of diverse resistivity is considered. TheE andH polarizations are treated in a similar way. The general solutions of the Helmholtz equation in the atmosphere is constructed. Far above the conductivity contrast the asymptotic form of the anomalous electromagnetic field is analytically found. It is proved that in theE-polarization case the asymptotic behaviour of the anomalous field differs very much from the generally assumed one. The conclusion of this paper is that in theE-polarization case the boundary conditions widely utilized in numerical computations are incorrect.

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Riassunto Si considera il problema dell'induzione nel caso di un conduttore bidimensionale inomogeneo che presenta un contatto verticale tra due mezzi di diversa resistività. Le polarizzazioniE eH sono trattate in modo simile. Si costruisce la soluzione generale dell'equazione di Helmholtz nell'atmosfera. Molto al di sopra del contrasto di conduttività, la forma asintotica del campo elettromagnetico anomalo è trovata analiticamente. Si prova che, nel caso della polarizzazioneE, il comportamento asintotico del campo anomalo differisce molto da quello generalmente considerato. La conclusione di questo lavoro è che nel caso della polarizzazioneE le condizioni al limite ampiamente usate nei calcoli numerici non sono corrette.

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Резюме Рассматривается проблема индукции в сличае неоднородното двумерного проводинка, представляющего вертикальный контакт между двумя средами с различными сопротивлениями.Е-иН-поляризации трактуются обычным образом. Конструируется общее решеиие уравнения Гельмгольца в атмосфере. Аналитически получена асимптотическая форма аномального електромагнитного поля значительно выше контраста проводимости. Доказывается, что в случаеЕ-поляризации асимптотическое поведение аномального поля сильно отличается от обычного поведения. В работе делается заключение, что в случаеЕ-поляризации граничные условия, широко используемые при численных вычислениях, не являются корректными.

     

偶极子在径向非均匀介质中的电磁场分布

提出了柱状多层介质中的磁偶极子在任意介质层中的电磁场的递推算法，给出了磁偶极子产生的电磁波在柱状多层介质中的反射、透射系数和广义反射系数，从而得到了任意介质层中满足各层界面边界条件的电磁场解析表达式．     

Heat exchange by fluctuating electromagnetic field between highly conductive tangentially inhomogeneous metals

A general expression is derived for the heat flux resulting from the fluctuating electromagnetic field between two highly conductive tangentially inhomogeneous (with properties that are functions of the coordinates of the surface point) metals heated to different temperatures that occupy half-spaces that are separated by a plane vacuum gap of arbitrary width a. The practically important particular case of a smooth dependence of the parameters of the metals on the tangential coordinates, in which the general expressions are greatly simplified, is studied in detail.     

The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction

The relation between corresponding trigonometric functions in two rotating coordinate systems is presented. The transformation formula for a vector in the two rotating spherical coordinate systems is obtained. The scattering fields for a spherical target irradiated by a plane electromagnetic wave in an arbitrary direction are derived. These fields in a particular case retrogress to those available in the literature. The obtained results have great potential in practical applications.     

Effects of aggregation on the electromagnetic resonance scattering of dielectric spherical objects

Summary The effects of aggregation on the electromagnetic resonance scattering by small, strongly reflecting spheres are studied. Two or more spheres are allowed to cluster together to form rather complicated anisotropic scatterers whose extinction cross-section is calculated as a function of the wave number of the incident field in the neighbourhood of the lowest resonance of the individual spheres. The macroscopic absorption coefficient of a low-density random dispersion of clusters is also calculated in the same range of wave number. The results for two-, three- and four-sphere clusters are discussed. Work supported in part by C.N.R. through the G.N.S.M. and in part by the U.S. Army European Research Office through grant DAJA45-84-C-0005 and contract DAJA37-81-C-0895.     

Electron in the field of two plane electromagnetic waves and an inhomogeneous electric field

This work examines the motion of an electron in an electromagnetic field consisting of the field of two plane electromagnetic waves of different frequencies ₁, ₂ and an electric fieldE'=(E₀ + E₃cos₃)e₃. The method of separation of variables is used to construct the solution of the Hamilton-Jacobi equation. The motion of the electron in the external electromagnetic field is described by those solutions of the Dirac equation coinciding with the eigenfunctions of the commutating operators.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 89–94, February, 1982.     

Multi-hybrid method for investigation of EM scattering from inhomogeneous object above a dielectric rough surface

An iterative strategy combining Kirchhoff approximation(KA) with the hybrid finite element-boundary integral(FE-BI) method is presented in this paper to study the interactions between the inhomogeneous object and the underlying rough surface.KA is applied to study scattering from underlying rough surfaces,whereas FE-BI deals with scattering from the above target.Both two methods use updated excitation sources.Huygens equivalence principle and an iterative strategy are employed to consider the multi-scattering effects.This hybrid FE-BI-KA scheme is an improved and generalized version of previous hybrid Kirchhoff approximation-method of moments(KA-MoM).This newly presented hybrid method has the following advantages:(1) the feasibility of modeling multi-scale scattering problems(large scale underlying surface and small scale target);(2) low memory requirement as in hybrid KA-MoM;(3) the ability to deal with scattering from inhomogeneous(including coated or layered) scatterers above rough surfaces.The numerical results are given to evaluate the accuracy of the multi-hybrid technique;the computing time and memory requirements consumed in specific numerical simulation of FE-BI-KA are compared with those of MoM.The convergence performance is analyzed by studying the iteration number variation caused by related parameters.Then bistatic scattering from inhomogeneous object of different configurations above dielectric Gaussian rough surface is calculated and the influences of dielectric compositions and surface roughness on the scattering pattern are discussed.     

Resonance radiation in electromagnetic wave scattering by a fast electron in the external magnetic field

The resonance radiation in Compton scattering of an electromagnetic wave by a fast relativistic electron moving in a given magnetic field is investigated with allowance for deceleration by the radiation. A general expression for the electric field of an arbitrarily polarized scattered wave is derived within the framework of small-perturbation theory. It is shown that the resonance peak in the scattering cross-section is caused by the small radiation friction. The dependence of the resonance line width on the characteristic parameters of the problem is examined. The scattering of a given polarized wave is considered, and the degree of linear polarization of the radiated wave under resonance is determined.Institute of Radiophysics and Electronics, Armenian Academy of Sciences, Erevan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 10, pp. 1001–1011, October, 1995.     

Scattering of spatially inhomogeneous sound waves by a spherical particle

The problem of monopole, dipole, and rotational scattering of a spatially inhomogeneous time-harmonic sound field by an arbitrary spherical particle is solved for the cases of the medium being a viscous compressible liquid or an isotropic elastic medium. Equations for the spherical mean fields at the particle are obtained. These equations are used to derive the formulas for the scattered fields. Different limiting cases of particle behavior are considered. In particular, it is shown that the dipole scattering is determined by two components of particle oscillations, one of which corresponds to translational oscillatory motion and the other to oscillations of two antiphase monopoles. For these types of particle oscillations, a scattering matrix, which determines the scattering of an arbitrary field by a particle, is constructed. The matrix allows the formalization of the processes of multiple sound scattering by particles and is valid for any distances between the particles down to their contact.     

Intensity of electromagnetic energy radiation by a quiescent ferromagnetic spherical particle placed in a permanent magnetic field

Technical Physics - The classical problem of calculating the energy of electromagnetic energy radiated from a ferromagnetic particle is solved for the case when the vector of spontaneous...