Propagation of electromagnetic waves in hot magnetoactive plasma

The paper derives the general form of the tensor of dielectric permittivity? _ij(ω,k), Eq. (15), of non-relativistic hot magnetoactive collisionless plasma taking into consideration the influence of spatial dispersion. The general form of the tensor? _ij(ω,k) is used to express the tensorε _ij(ω,k) in the region of weak and strong spatial dispersion and in some special cases. A general dispersion equation (30) is derived and an analysis is made of the waves propagating in hot magnetoactive plasma. The expressions derived are used to investigate the damping of a right-handed circularly polarized wave propagating in hot magnetoactive plasma in the direction of the magnetic field.     

Localization of intense electromagnetic waves in a relativistically hot plasma

We consider nonlinear interactions between intense short electromagnetic waves (EMWs) and a relativistically hot electron plasma that supports relativistic electron holes (REHs). It is shown that such EMW-REH interactions are governed by a coupled nonlinear system of equations composed of a nonlinear Schro dinger equation describing the dynamics of the EMWs and the Poisson-relativistic Vlasov system describing the dynamics of driven REHs. The present nonlinear system of equations admits both a linearly trapped discrete number of eigenmodes of the EMWs in a quasistationary REH and a modification of the REH by large-amplitude trapped EMWs. Computer simulations of the relativistic Vlasov and Maxwell-Poisson system of equations show complex interactions between REHs loaded with localized EMWs.     

Diffraction of electromagnetic waves by a nonconducting half-plane in a hot plasma

The diffraction of transverse and longitudinal plane waves by a thin nonconducting perfectly rigid half-plane in a hot plasma is examined. The general solution of the problem and asymptotic formulas for the far zone are found. It is shown that they are significantly simplified for frequencies well above the plasma frequency. The behavior of the field near the edge is analyzed.St. Petersburg State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 12, pp. 1503–1511, December, 1994.     

Experimental and theoretical study of crude oil pretreatment using low-frequency ultrasonic waves

In this work, an ultrasound experimental setup was designed to investigate the feasibility of using low-frequency ultrasonic waves as a substitute to reduce the consumption of chemical demulsifiers in the pretreatment of crude oil. The experiments were planned to study the effects of irradiation time, ultrasonic field intensity and initial water content on the efficiency of separation. The results of experiments showed that by selecting a proper irradiation time and field intensity, it is possible to decrease the usage of demulsifiers by 50%. Moreover, a population balance model was proposed to explicate the experimental data. A hybrid coalescence model was developed to determine the frequency of aggregation. The parameters of the model were estimated by linear regression. The parameter estimation was performed using a parallel execution of the particle swarm optimization algorithm. The results of the model showed a decent agreement with the experimental data.     

Ion acoustic waves in the presence of electron plasma waves

Long-wavelength ion acoustic waves in the presence of propagating short-wavelength electron plasma waves are examined. The influence of the high frequency oscillations is to decrease the phase velocity and the damping distance of the ion wave.     

Instability of plasma waves in an electromagnetic field

Summary In the presence of a weak laser field the plasma scattering by electrons is discussed.

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Riassunto In presenza di un campo laser debole, si discute la diffusione del plasma mediante elettroni.

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Резюме В присутствии слабого лазерного поля обсуждается рассеяние плазмы на электронах.

     

The coherence of low-frequency sound in shallow water in the presence of internal waves

The coherence time and transverse coherence length of a low-frequency (100–300 Hz) sound field that is formed by an omnidirectional point source at a distance of 10–30 km in a shallow-water acoustic waveguide, which is characteristic of an open ocean shelf, were estimated analytically and in a numerical experiment. An anisotropic field of background internal waves is considered as a source of spatiotemporal fluctuations. It is shown that the coherence time decreases as the frequency increases, and strongly depends on the perturbation-movement direction. The transverse coherence length is primarily determined by phase incursions that are related to the cylindrical shape of the acoustic-wave front. In the case of transverse propagation, background internal waves may lead to significant variations in this length. The introduction of compensating phase corrections during processing provides a considerable increase in the average transverse coherence length.     

Penetration of electromagnetic waves into magnetoactive plasma

Landau studied the longitudinal field penetration into a semi-bounded plasma considering specularly reflecting electrons at the boundary. Kurilko and Popov and then Gorman examined the same problem considering a fraction “p” of all incident electrons reflecting specularly and the remaining portion difusely. Lastly, Mason treated the same problem at length and gave solutions for specular and diffuse reflections. Here the penetration of transverse electromagnetic waves into magnetoactive semi-bounded plasma has been studied and the electric field for specular reflection of electrons is obtained.     

Low frequency electromagnetic waves in a multi-ion plasma

The dispersion characteristics of low-frequency electromagnetic waves are studied in a plasma containing hydrogen ions and positively and negatively charged oxygen ions and electrons. This composition of the plasma approximates very well the coma of comet Halley where many heavy ions have been observed in appreciable numbers. The excitation of these waves results from the relative motion between the protons and the heavy ions, which are considered unmagnetised and, therefore, may act like a beam. We find that the wave growth increases with increasing heavy ion densities, beam velocities and propagation angles.     

Diffraction and propagation of electromagnetic waves in the presence of chiral media

The propagation of electromagnetic waves in infinite, semiinfinite, and laminar chiral structures is investigated, along with the diffraction of electromagnetic waves on semiinfinite objects in a chiral medium and three-dimensional objects consisting entirely or partially of chiral materials. Particular attention is paid to diffraction on three-dimensional uniform chiral bodies and ideally conducting bodies covered by chiral shells. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 50–61, August, 1998.