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  • 1
    Electronic Resource
    Electronic Resource
    On the structural stability of magnetic configurations with two null lines (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 802-815 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonlinear dynamics of magnetoacoustic and Alfvén-type magnetohydrodynamic (MHD) perturbations in structurally unstable magnetic configurations is studied analytically and numerically. The nonlinear evolution of the perturbed electric current turns structurally unstable configurations into structurally stable ones. This transformation is forbidden in the framework of the ideal MHD equations, but can occur in the process of magnetic field line reconnection. MHD simulations of the transformation of configurations with two null lines (X-lines) under perturbations imposed from the boundaries show that the change in the magnetic field topology due to the magnetoacoustic perturbations is accompanied by the redistribution of the electric current curried by the Alfvén perturbations.© 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873320
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of an ultrashort, relativistically strong laser pulse with an overdense plasma (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 745-757 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of an analytical description and of a particle-in-cell simulation of the interaction of an ultrashort, relativistically intense laser pulse, obliquely incident on a nonuniform overdense plasma, are presented and several novel features are identified. The absorption and reflection of the ultraintense electromagnetic laser radiation from a sharp-boundary plasma, high harmonic generation, and the transformation into low-frequency radiation are discussed. In the case of weak plasma nonuniformity the excitation of nonlinear Langmuir oscillations in the plasma resonance region and the resulting electron acceleration are investigated. The vacuum heating of the electrons and the self-intersection of the electron trajectories are also studied. In the case of a sharp-boundary plasma, part of the energy of the laser pulse is found to be converted into a localized, relativistically strong, nonlinear electromagnetic pulse propagating into the plasma. The expansion of the hot electron cloud into the vacuum region and the action of the ponderomotive force of the laser pulse in the localized longitudinal electric field of the Langmuir oscillations lead to ion acceleration. The energy increase of a minority population of multicharged ions is found to be much greater than that of the ambient ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870766
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  • 3
    Electronic Resource
    Electronic Resource
    Ionization rate in the presence of runaway electrons (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 931-939 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of a fast electron population, produced by the strong electric field driving the axial current in a capillary discharge, can be essential in order to justify the appreciable concentration of highly charged C ions (C5+, C6+) as observed in many experiments with low electron temperature. Under the assumption that a quasistationary state is established during the discharge, the runaway electron distribution function is determined analytically for Zeff〉1, following the approximated method developed by Lebedev [A. N. Lebedev, Sov. Phys. JETP 21, 931 (1965)]. The strong enhancement of the ionization rate, due to the presence of an electron tail in the energy range of the ionization potential, is then demonstrated. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872188
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  • 4
    Electronic Resource
    Electronic Resource
    Nonlinear depletion of ultrashort and relativistically strong laser pulses in an underdense plasma (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1935-1942 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The depletion of a relativistically strong laser pulse in the course of interaction with underdense plasmas is considered. The driving mechanisms of distortion and fast depletion of the pulse due to the nonlinear plasma wake excitation are discussed. The role of the backward stimulated Raman scattering in the process of the leading front steepening is traced. Electron acceleration and heating due to plasma wave breaking are demonstrated. The evidence that the final stage of the pulse depletion can be accompanied by the formation of relativistically strong solitonlike electromagnetic modes is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860046
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetic reconnection in electron magnetohydrodynamics (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2499-2508 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic field dynamics and reconnection processes in a highly conducting plasma are investigated in the regimes where Ohm's law is dominated by the Hall term, using a single (electron) fluid description (electron magnetohydrodynamics). In these regimes, which correspond to the frequency range of the so-called whistler (helicon) mode, the electromagnetic field is nearly force free: (j×B)/c+eneE=0. The evolution of the magnetic field in the vicinity of an X line is discussed in the linear and nonlinear regimes. The propagation of whistler waves results in the steepening of their wave front and in the increase of the electric current density in the neighborhood of the magnetic separatrix surfaces. Small-scale magnetic reconnection occurs near surfaces where k⋅B=0, with k the mode wave number, and tearing-type modes can be unstable due to the effect of electron inertia. A class of exact self-similar solutions is obtained. These describe, within the scope of a local approximation, the nonlinear time development (magnetic collapse) of the singularities that occur in three-dimensional magnetic configurations. Flat electric current sheets are formed during this collapse. Finally, the rate of reconnection in the electron-magnetohydrodynamic frequency range is estimated in the framework of a steady-state approximation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860467
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  • 6
    Electronic Resource
    Electronic Resource
    Particle simulations of boundary-condition and hf-field effects on strong double layers in a collisionless bounded plasma (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2871-2884 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of electrostatic double layers (DL's) in a collisionless plasma diode with injection of current-carrying plasma from both ends is systematically investigated by means of particle-in-cell simulations. These simulations have been performed with the one-dimensional electrostatic bounded-plasma codes PDW1 [J. Comput. Phys. 80, 253 (1989)] and PDP1 [J. Appl. Phys. 69, 2008 (1991)]. It is found that asymmetry in the injection conditions can shift the DL toward one of the boundaries and may either stabilize or destabilize it. If a given dc potential difference is applied between the electrodes and a time-independent DL exists, the latter is always found to be adjacent to the low-potential boundary of the diode. Application of a strong hf field, modeled by an ac bias, can lead to stabilization or destabilization of the DL, depending on the driving frequency. For boundary conditions corresponding to a given constant external-circuit current, the DL's observed in the simulations are transient and decay on the time scale on which the diode fills with plasma. Of particular interest is the fact that in none of the simulations reported has a time-independent DL separating two extended regions of quasineutral plasma been obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860161
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  • 7
    Electronic Resource
    Electronic Resource
    Generation of Magnetic Field and Fast Particles During Collision of Electron-Positron Plasma Clouds (1998)
    Springer
    Astrophysics and space science 264 (1998), S. 381-390 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present results of analytical studies and 2D3V PIC simulations of electron-positron plasma cloud collisions. We concentrate on the problem of quasi-static magnetic field generation. It is shown from linear theory, using relativistic two-fluid equations for electron-positron plasmas, that the generation of a quasi-static magnetic field can be associated with the counter-streaming instability. A two-dimensional relativistic particle simulation provides good agreement with the above linear theory and that, in the nonlinear stage of the instability, about 5.3% of the initial plasma flow energy can be converted to magnetic field energy. It is also shown from the simulation that the quasi-static magnetic field undergoes a collision-less change of structure, leading to large scale, long living structures and the production of high-energy particles. These processes may be important for understanding of production of high-energy particles in the region where two pulsar winds collide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1002400520195
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  • 8
    Electronic Resource
    Electronic Resource
    Low-frequency relativistic electromagnetic solitons in collisionless plasmas (1998)
    Springer
    JETP letters 68 (1998), S. 36-41 
    Details
    ISSN: 1090-6487
    Keywords: 52.40.Nk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A relativistic electromagnetic soliton solution in the model of a one-dimensional, unbounded, cold, collisionless plasma is obtained without using the envelope approximation. The breaking of solitons with over-critical amplitudes is observed. The stability of undercritical solitons and the breaking of overcritical solitons are demonstrated by a particle-in-cell computer simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.567817
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  • 9
    Electronic Resource
    Electronic Resource
    Ion acceleration by superintense laser pulses in plasmas (1999)
    Springer
    JETP letters 70 (1999), S. 82-89 
    Details
    ISSN: 1090-6487
    Keywords: 52.65.Rr ; 52.40.Nk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ion acceleration by petawatt laser radiation in underdense and overdense plasmas is studied with 2D3V-PIC (Particle in Cell) numerical simulations. These simulations show that the laser pulse drills a channel through the plasma slab, and electrons and ions expand in vacuum. Fast electrons escape first from the electron-ion cloud. Later, ions gain a high energy on account of the Coulomb explosion of the cloud and the inductive electric field which appears due to fast change of the magnetic field generated by the laser pulse. Similarly, when a superintense laser pulse interacts with a thin slab of overdense plasma, its ponderomotive pressure blows all the electrons away from a finite-diameter spot on the slab. Then, due to the Coulomb explosion, ions gain an energy as high as 1 GeV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568134
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  • 10
    Electronic Resource
    Electronic Resource
    Generation of collimated beams of relativistic ions in laser-plasma interactions (2000)
    Springer
    JETP letters 71 (2000), S. 407-411 
    Details
    ISSN: 1090-6487
    Keywords: 52.40.Nk.408
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A method is proposed for generating collimated beams of fast ions in laser-plasma interactions. Two-dimensional and three-dimensional particle-in-cell simulations show that the ponderomotive force expels electrons from the plasma region irradiated by a laser pulse. The ions with unneutralized electric charge that remain in this region are accelerated by Coulomb repulsive forces. The ions are focused by tailoring the target and also as a result of pinching in the magnetic field produced by the electric current of fast ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.568365
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