Browsing by Author "Rudakov, Leonid"

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    Model for nonlinear evolution of localized ion ring beam in magnetoplasma
    Scales, Wayne A.; Ganguli, Gurudas; Rudakov, Leonid; Mithaiwala, Manish (AIP Publishing, 2012-06-01)
    An electrostatic hybrid model, which investigates the nonlinear evolution of a localized ion ring beam in a magnetoplasma, is described and applied to the generation and evolution of turbulence in the very low frequency (VLF) (Omega(ci) < omega < Omega(ce)) range, where Omega(ci(e)) is the ion (electron) gyro frequency. Electrons are treated as a fluid and the ions with the particle-in-cell method. Although the model is electrostatic, it includes the effects of energy loss by convection of electromagnetic VLF waves out of the instability region by utilizing a phenomenological model for effective collisions with the fluid electrons. In comparison with a more conventional electrostatic hybrid model, the new model shows much more efficient extraction of energy from the ion ring beam and reduced background plasma heating over a range of parameters. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729330]
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    Three dimensional character of whistler turbulence
    Ganguli, Gurudas; Rudakov, Leonid; Scales, Wayne A.; Wang, Joseph J.; Mithaiwala, Manish (AIP Publishing, 2010-05-01)
    It is shown that the dominant nonlinear effect makes the evolution of whistler turbulence essentially three dimensional in character. Induced nonlinear scattering due to slow density perturbation resulting from ponderomotive force triggers energy flux toward lower frequency. Anisotropic wave vector spectrum is generated by large angle scatterings from thermal plasma particles, in which the wave propagation angle is substantially altered but the frequency spectrum changes a little. As a consequence, the wave vector spectrum does not indicate the trajectory of the energy flux. There can be conversion of quasielectrostatic waves into electromagnetic waves with large group velocity, enabling convection of energy away from the region. We use a two-dimensional electromagnetic particle-in-cell model with the ambient magnetic field out of the simulation plane to generate the essential three-dimensional nonlinear effects. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3420245]