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  • 1
    Digitale Medien
    Digitale Medien
    Anomalous electron precipitation near the Earth's auroral zone induced by the wave–particle interaction (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2269-2275 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The results of a numerical simulation of anomalous electron precipitation in the Earth's auroral zone induced by waves are discussed. In order to study the plasma electron–wave interaction, a two-dimensional quasilinear code has been used. A quasilinear operator models the electron Landau damping of any plasma eigenmodes: kinetic Alfvén waves, whistlers, lower hybrid waves, etc. The distribution function structure was analyzed. The electron current induced by waves, the density, and the plasma energy decay, which stimulates the electron precipitation, have also been investigated. © 1997 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.872390
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  • 2
    Digitale Medien
    Digitale Medien
    Alfvén waves and rotation of collisional plasmas in tokamaks (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2818-2820 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The effect of radio frequency fields on a plasma rotation in the edge (collisional) region of slightly rippled tokamaks is considered. The expressions for poloidal and toroidal velocities and for quasistationary radial electric fields are obtained as a function of absorbed rf power. The estimations of these quantities for the Phaedrus-T tokamak [N. Hershkovitz et al., 15th International Atomic Energy Agency Conference on Plasma Physics and Controlled Fusion, Seville, 1994 (International Atomic Energy Agency, Vienna, in press)] are also presented. It is shown that Alfvén waves can strongly modify the rotation velocities and radial electric fields in collisional regions of tokamak plasmas. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871716
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  • 3
    Digitale Medien
    Digitale Medien
    Influence of trapped electrons on the dielectric properties of the Earth's radiation belts (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 3798-3808 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The dielectric tensor of an axisymmetric magnetosphere is derived by solving the Vlasov equations for trapped particles for a two-dimensional plasma model with circular magnetic field lines. Because of the nonuniformity of the geomagnetic field any Fourier harmonic of the perturbed current density (after its Fourier expansion over the geomagnetic latitude) is proportional to the sum over all harmonics of the oscillating electric field; that leads to additional wave dissipation effects. The resonant conditions for wave–particle interactions are discussed taking into account the cyclotron and bounce resonances; these conditions in magnetospheric plasmas are entirely different from the Landau damping resonant factor in the uniform magnetic field. The numerical calculations of the longitudinal permeability in the Earth's radiation belts (the equatorial distance of the magnetic field line is five Earth's radii) are carried out for short-period oscillations with the frequency ω∼2 s−1 and longitudinal wave numbers n=1,...,15. The different energy levels of the trapped electrons, T∼40–4000 eV, are considered. It is shown that, in the low-frequency region, the imaginary part of the longitudinal permeability decreases as ∼T−2.5 whereas the electron temperature increases. This decrease is stronger than ∼T−1.5 for plasmas in a straight magnetic field. For a given wave frequency, the basic contribution of trapped electrons to the imaginary part of longitudinal permeability is associated with the low numbers of bounce resonances and the low longitudinal wave numbers. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871512
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  • 4
    Digitale Medien
    Digitale Medien
    Alfvén wave heating and current drive : The 42nd annual meeting of the division of plasma physics of the American Physical Society and the 10th international congress on plasma physics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 2050-2056 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Progress in the theory of Alfvén wave (AW) heating, current drive, and plasma flow, which may be relevant for improved confinement scenarios in tokamaks, is discussed. The effect of poloidal mode coupling on the power deposition of AW eigenmodes is investigated. Resonant absorption of the coupled side bands causes a broad power deposition close to the plasma boundary which can surpass the power deposition of the main global AW at the plasma center. A small population of impurities, such as carbon, in a hydrogen plasma can strongly modify the dispersion of the global AW, the AW continuum and the wave dissipation profile. The ponderomotive forces produced by rf fields are expressed as a sum of a gradient (radial derivative) part and of a wave momentum transfer force found to be proportional to wave dissipation. Finally, the rf force is balanced by the friction (or neo-classical viscosity) force to calculate relevant current drive and plasma specie flows. Estimates of AW power requirements to drive substantial heating, current, and poloidal flow are made for plasmas in the Tokamak Chauffage Alfvén wave experiment in Brazil (TCABR) [L. Ruchko et al., Nucl. Fusion 30, 503 (1996)]. The first results of Alfvén wave heating and current drive experiments with a low level of wave dissipation in the TCABR are discussed. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1350572
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  • 5
    Digitale Medien
    Digitale Medien
    The Coulomb scattering effect on trapped particles bounce-resonance dissipation in magnetized toroidal plasmas (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1547-1553 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The solution of the Vlasov equation with a simplified Fokker–Planck collision operator is presented for axially symmetric tokamak plasmas with a circular cross section of magnetic surfaces. The analytical expression for the parallel component of the dielectric permittivity tensor of trapped particles is obtained. This expression is used for theoretical analyses of the collision effect on the bounce-resonance wave dissipation. Conditions for a collisionless description of radio-frequency (rf) oscillations are found. This dielectric tensor components can be used for computer calculations of the rf field structure and the rf dissipated power related to trapped electrons in tokamak plasmas. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873408
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  • 6
    Digitale Medien
    Digitale Medien
    Anomalous and neoclassical transport suppression by the radial electric field, induced by Alfvén waves in tokamaks (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 3548-3553 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The suppression of anomalous transport and/or reduction of neoclassical transport caused by the Alfvén-wave-induced shear of the radial electric field in tokamaks is investigated. The simple quantitative estimates reported in previous papers are checked by a consistent evaluation of the profile of the radial electric field created by the resonant absorption of Alfvén waves. The radial variations of the ion viscosity and heat conductivity across the mode conversion layer are evaluated both in the banana and potato regions. In agreement with previous analytical results, it is shown that the kinetic Alfvén waves may play the role of a convenient mechanism for reduction of anomalous and neoclassical transport and formation of transport barriers in tokamaks. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.873615
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  • 7
    Digitale Medien
    Digitale Medien
    Hydrodynamic description of Alfvén and fast wave current drive in weakly collisional plasmas of magnetic traps (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2784-2789 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this paper, general aspects of the Alfvén and fast wave nonresonant and resonant current-drive problem are considered both for collisional and weakly collisional plasmas. The magnetohydrodynamic approach is used for all collisional regimes and Landau damping is taken into account in the weakly collisional plasma case. Averaged in time and over magnetic surface, the general form of current-drive forces are derived, including the viscosity and collision frequency perturbation terms. As an example, a weakly collisional plasma cylinder case is discussed and some disagreements on this problem between different authors results are eliminated. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.871176
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  • 8
    Digitale Medien
    Digitale Medien
    Radial plasma transport and toroidal current driven by nonresonant ponderomotive forces (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2882-2889 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A general form of the time-averaged ponderomotive force produced by radio frequency waves in magnetized plasma configurations is treated. Included in the ponderomotive force are components that result from plasma flow, the dynamo effect, and wave helicity. A detailed description of effects of individual components in the ponderomotive force on radio frequency (RF) driven transport and current is given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.870528
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  • 9
    Digitale Medien
    Digitale Medien
    Calculations of Alfvén wave driving forces, plasma flow, and current drive in the Tokamak Chauffage Alfvén wave experiment in Brazil (TCABR) (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 210-215 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The current and plasma flows driven by ponderomotive forces are calculated for tokamak plasmas, using a kinetic code in the Alfvén range of frequencies. The rf (radio frequency) ponderomotive force is expressed as a sum of a gradient part and of a wave momentum transfer force, which is proportional to wave dissipation (electron Landau damping and transit time magnetic pumping). Finally, the rf force is balanced by the viscous force in the fluid momentum response to the rf fields in the plasma. The relative magnitudes of the different forces for kinetic and global Alfvén waves with low phase velocities are explicitly calculated. It is shown that, dissipating in electrons, Alfvén waves can drive ion flow via the gradient force, which is dominated in m=0-sideband harmonic resonance induced by toroidal mode coupling. Estimates of power requirements to drive substantial poloidal flow in the Tokamak Chauffage Alfvén wave heating experiment in Brazil (TCABR) [L. Ruchko, M. C. Andrade, R. M. O. Galva˜o, Nucl. Fusion 30, 503 (1996)] are made. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1332813
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  • 10
    Digitale Medien
    Digitale Medien
    Comment on "Alfvén wave current drive in tokamak rotating plasma with negative magnetic shear" [Phys. Plasmas 6, 4633 (1999)] (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3119-3119 
    Details
    ISSN: 1089-7674
    Quelle: AIP Digital Archive
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.874170
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