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  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Optics and Lasers in Engineering 18 (1993), S. 307-324 
    ISSN: 0143-8166
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics , Technology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6805-6805 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently it was shown that the light absorption spectrum of (CH2)2(NH3)2MnCl4 (EDAMnCl4) differs strongly from those of other compounds of this family (CH2)n(NH3)2MnCl4. Additional peculiarities in the spectral distributions of two-magnon Raman scattering and the coefficient of exciton-magnon absorption were found. It was also determined that the pure exciton band in the absorption spectrum is of the electric dipole type of polarization. All these peculiarities are out of the framework of the usual tetragonal two-sublattice antiferromagnet model and indicate the inverse center loss and magnetic cell doubling. Results of studying the absorption spectrum of EDAMnCl4 presented in the report show that not less than three Davydov components of the exciton band σA1g(σS)→4Eg(4G) optical transition may be detected with confidence in magnetic fields oriented along the c axis. It confirms the four-sublattice magnetic structure of EDAMnCl4. The presence of exciton line splitting at H=0 and its nonlinear character at H(parallel)α (that is practically parallel to l) allows us to make a conclusion about the resonance interaction between ions with antiparallel spins and, probably, about the initial noncollinearity of magnetic structure. Parameters characterizing the magnetic Davydov splitting are determined using comparison of the experimental data and theoretical analysis.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 516-526 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper numerical solutions of Zakharov-type equations for lower-hybrid (LH) waves, including pumping at the long wavelengths and dissipation at short wavelengths in the form of dissipative cavitons are described. The caviton is a quasistationary structure undergoing many sequences of collapse due to dissipation, created by ion–wave interactions, which is compensated for by constant pump action. The possibility of trapping of short-wavelength LH oscillations by much broader density cavitons is investigated both analytically and numerically. Analytic self-similar solutions corresponding to collapse of such cavitons are constructed and demonstrate cascading to shorter wavelengths, which develops faster than the three-dimensional (3-D) quasiclassical cavity contraction. Numerical solutions show the development of deep caviton modulation due to the instability of quasiclassical collapse. Results of the numerical and analytical investigation are used to explain the recent observations of cavity formation in the auroral ionosphere, and show that the measured structures could indeed arise from quasiclassical LH collapse. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The linear and nonlinear dynamics of modulational interaction between small-scale drift waves and large-scale trapped ion convective cells are investigated. This example is a paradigm of the more general problem of describing the self-consistent interaction of small-scale fluctuations with mean sheared flows. The growth rate of modulational instability is determined by spectral properties of drift waves and can exceed the linear growth rate of the trapped ion mode. An anisotropic spectrum of drift waves is always modulationally unstable. The spatial orientation of the convective cell pattern and structure (i.e., shear strength) is determined by drift wave spectrum anisotropy and propagation direction. In the presence of a sheared magnetic field, which pins small-scale drift waves to mode rational surfaces, the modulational growth rate becomes intrinsically anisotropic, on account of the modified radial structure of drift waves. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 222-224 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tilting instability is an instability of convective motion in two-dimensional (2-D) ideal fluid transforming convection into sheared flow. An analytical model of the tilting instability is proposed that clearly exhibits inverse cascade phenomenon, conserving both energy and enstrophy. Obtained solution describes the evolution of the nonlinear stage in which initial fluid convection is transformed completely into the large-scale flow.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 654-677 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments are described on the interaction of a weak warm beam with a broad spectrum of unstable waves on a traveling wave tube. The wave–particle interactions are similar to those in beam–plasma systems, and are traditionally described by quasilinear theory. The precise wave evolution is obtained by launching a specified waveform, allowing it to interact with the beam, and analyzing the received waveform. Significant mode coupling is observed, resulting in saturated waves correlated less than 0.5 with their launch values. Experimentally, each wave is separated into a component proportional to the launch amplitude and a component due solely to mode coupling. The measured properties of these separate components agree quantitatively with a four-wave coupling model. Strongest coupling is observed between waves whose wave numbers match within about an inverse turbulent trapping length. In the linear growth regime, the measured ensemble-averaged wave growth rates and beam velocity diffusion rates agree reasonably with quasilinear and resonance-broadening theory; in the nonlinear regime near saturation, the discrepancies become larger. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3148-3162 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The modulational instability and collapse of waves in the vicinity of the lower-hybrid resonance including both magnetosonic and lower-hybrid waves are investigated by analytical and numerical methods. The mechanism leading to the modulational instability is the nonlinear coupling of lower-hybrid waves with the much lower-frequency quasineutral density perturbations via the ponderomotive force. The result is a filamentation of the high-frequency field producing elongated, cigar-shaped nonlinear wave packets aligned along the magnetic field with the plasma expelled outside (cavities). The analytical self-similar solutions describing cavity collapse are obtained and compared with the results of numerical simulation for both two- and three-dimensional cavity geometries. It is shown that in three-dimensional solutions the transverse, with respect to the magnetic field, contraction remains prevailing. The possibility of ion acceleration as the result of the lower-hybrid collapse is discussed and detailed comparison is made with the observations of the phenomena in the auroral ionosphere.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The comments of Montgomery and Matthaeus on the authors' paper1, have been answered. The results do not contradict those of Montgomery and Matthaeus but for simple case considered, transition to shear flow state and shape of initial vortices is explained. (AIP)
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1728-1738 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: One of the main experiments of the Active Magnetospheric Particle Tracer Explorers (AMPTE) [J. Geophys. Res. 91, 10013 (1986)] satellite mission was the release of neutral barium atoms in the solar wind. The barium atoms ionized by photoionization extremely rapidly forming a dense, expanding, plasma cloud that interrupted the solar wind flow creating diamagnetic cavities. On the upstream side of the cavity a region of compressed plasma and enhanced magnetic field was created as the result of being produced by the slowing down and deflection of the solar wind, and magnetic field line draping. Intense electrostatic and magnetic turbulence was observed by both the IRM [J. Geophys. Res. 91, 10 013 (1986)] and UKS [J. Geophys. Res. 91, 1320 (1986)] satellites at the boundary of the diamagnetic cavity, with the most intense waves being detected near the outer boundary of the compressed region. This paper examines how the newly created expanding plasma couples to the solar wind by means of plasma–beam and current-driven instabilities. In particular, it is shown how lower-hybrid and lower-hybrid drift waves are generated by cross-field proton–barium streaming instabilities and cross-field electron currents. The saturation mechanism for these waves is considered to be the modulational instability, this instability can also lead to filamentation and coupling to magnetosonic modes, which are also observed. As the result of modulational instability the k(parallel) component increases, which allows the heating and acceleration of electrons that is consistent with the observations.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 3562-3568 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents a model of beam–plasma discharge resulting from the quasilinear heating of plasma electrons by Langmuir waves which are excited by beam–plasma interactions. The heating is made possible by the spectral transformation of waves propagating radially from the central beam-occupied region toward the region of lower plasma density. In this paper equations describing the wave spectral density, the distribution function of a high-energy electron tail, and its stationary density profile are obtained and numerically solved; to do so a balanced diffusion and ionization is assumed. The possibility of significant plasma density enhancement in beam–plasma discharge is demonstrated.
    Type of Medium: Electronic Resource
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