Whistler Wave Emission from a Modulated Electron Beam in a Collisional Magnetoplasma in the Presence of a Density Duct

We study the radiation from a modulated electron beam injected along the axis of a cylindrical density duct in a magnetoplasma. An expression for the average power lost by the beam at the modulation frequency is obtained and analyzed. It is shown that in the case of Cerenkov resonance of the beam with a weakly damped whistler mode of an enhanced-density duct, a noticeable increase in this power is possible compared with the case where the beam is injected in a homogeneous background magnetoplasma. Based on the results of numerical calculations performed for conditions of the Earth's ionosphere, we give estimates of an increase in the power radiated from the beam in the whistler frequency range in the presence of a cylindrical duct with enhanced density. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 730–742, September 2005.     

Whistler channeling in ducts with enhanced density in a magnetoactive plasma

We study the guided propagation of whistler waves along the density ducts created in a magnetoactive plasma under thermal nonlinear conditions. It is found that the thermal diffusion-driven redistribution of plasma due to electron heating in the quasistatic field of a current loop of fairly large radius leads to the formation of a duct with enhanced density. Based on experimental data and theoretical calculations, it is shown that such a duct can sustain the weakly decaying whistler modes excited by a magnetic-type antenna immersed in it. Radiophysical Research Institute, Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 3, pp. 384–394, March, 1998.     

Cylindrical electromagnetic waves in a nonlinear nondispersive medium: Exact solutions of the Maxwell equations

The excitation and propagation of cylindrical electromagnetic waves in a nonlinear nondispersive medium are analyzed. It is assumed that the medium lacks a center of symmetry and that the dependence of the electric displacement on the electric field can be approximated by an exponential function. For this case, a method for integrating the system of the Maxwell equations is proposed. Exact solutions to a set of nonlinear electromagnetic field equations are obtained by this method. It is shown that nonlinear effects described by these solutions can become apparent under experimental conditions.     

Phase Separation in GaMnAs Layers Grown by Laser Pulsed Deposition

GaMnAs layers grown by pulsed laser deposition were studied by magneto-optical transversal Kerr effect spectroscopy, spectral ellipsometry, resistivity and the Hall effect measurements, and magnetometry. The growth regimes for magnetically inhomogeneous layers containing Mn-enriched ferromagnetic regions with different composition and sizes were established. The layers grown at a temperature of 300°C exhibit a ferromagnetic behavior at temperatures below 80 K, which is conditioned by the presence of local ferromagnetic (Ga,Mn)As regions in the paramagnetic matrix. The nature of peculiarities in the TKE spectrum of these layers is discussed.     

Radiation of whistler-band wares in magnetoactive plasma. II

The whistle-band radiation of the ring magnetic current in a magnetoactive plasma is studied. Principal attention is given to the dependence of the distribution of the radiated power over the space spectrum of the excited plane waves (whistlers conical-refraction waves, and plasma waves) on the radiator dimensions and the magnetic-field distribution over the ring. It is shown that most of the power radiated by ring magnetic currents in the examined frequency band goes into plasma waves, regardless of the radiator dimensions.Scientific-Research Radio-Physics Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35 No. 8, pp. 631–640, August, 1992.     

Structure of the electromagnetic fields of loop radiators in magnetized plasmas over the whistler frequency range

The role of different sections of the spatial spectrum of whistler waves excited by a loop antenna in the formation of an electromagnetic field structure is investigated experimentally and theoretically. Primary attention is given to the intermediate range of distances between the source and the observation point.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 2, pp. 192–202, February, 1996.T. M. Zaboronkova, A. V. Kostrov, A. I. Smirnov, and A. A. Shaikin are grateful to The Russian Foundation for Fundamental Research (Grant No.94-02-05447a) and the George Soros International Foundation (Grant No. NOP 300) for financial support. A. V. Kudrin is grateful to the Russian Fund for Fundamental Research (Grant No. 96-02-18666) for financial support.     

Formation of spin light-emitting diodes based on InGaAs/GaAs heterostructures containing ferromagnetic inclusions

The electroluminescence of light-emitting diodes based on heterostructures with InGaAs quantum wells and a delta 〈Mn〉 doped layer in the GaAs barrier is studied. It is shown that the diodes emit circularly polarized light with the degree of polarization depending on the applied magnetic field and on temperature. We assume that the temperature dependences of the degree of polarization are determined by a change in the mutual position of energy levels of Mn ions in the delta layer and of holes in a quantum well.