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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1437-1446 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quasifluid formalism designed to capture some effects of cyclotron interactions is presented. Starting from the contractions of exact moments of the Vlasov equation, a closure for cyclotron interactions is achieved by using kinetic information directly. This nonperturbative approach does not require a priori assumptions about zeroth-order particle velocity distributions. The nonlinear coupling between field-aligned particle thermal velocities and transverse cyclotron wave and thermal motions are described by off-diagonal elements of the pressure tensor. These elements are related to the growth and damping of cyclotron wave energy. A functional form for an effective wave–particle momentum transport coefficient is derived from the requirement of consistency between the energy and momentum moment equations, but its specific magnitude and sign, determined by threshold temperature anisotropy levels, must be input from kinetic theory. This effective transport coefficient has a nondefinite sign, reminiscent of the gyroviscous coefficients of classical transport, and is consistent with the time reversibility of the Vlasov equation. A coupled set of cyclotron equations of state for the evolution of the parallel and perpendicular pressures are derived. This formalism provides a connection between known kinetic solutions of cyclotron interactions and fluid plasma equations. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2011-08-24
    Description: Magnetohydrodynamic (MHD) simulation are used to provide a dynamical basis for the 'vortex street' model of the quasi-periodic meridional flow observed by Voyager 2 in the outer heliosphere. Various observations suggest the existence near the current sheet at solar minimum, of a vorticity distribution of two opposite shear layers with an antisymmetric staggered velocity pattern due to structured high-speed wind surrounding low-speed equatorial flow. It is shown that this flow pattern leads to the formation of a highly stable vortex street through the nonlinear interaction of the two shear layers. Spatial profiles of various simulated parameters (velocity, density, meridional flow angle and the location of magnetic sector boundaries) and their relative locations in the quasi-steady vortex street are generally in good agreement with the observations.
    Keywords: SOLAR PHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 14, J
    Format: text
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  • 3
    Publication Date: 2011-08-24
    Description: We study a transverse plasma flow induced by the evolution of a Karman vortex street using a Chebyshev-Fourier spectral algorithm to solve both the compressible Navier-Stokes and MHD equations. The evolving vortex street is formed by the nonlinear interaction of two vortex sheets initially in equilibrium. We study spatial profiles of the total plasma velocity, the density, the meridional flow angle and the location of sector boundaries and find generally good agreement with Voyager 2 measurements of quasi-periodic transverse flow in the outer heliosphere. The pressure pulses associated with the meridional flows in the simulation are too small, although they are correctly located, and this may be due to the lack of any 'warp' in the current sheet in this model. A strong, flow-aligned magnetic field, such as would occur in the inner heliosphere, is shown to lead to weak effects that would be masked by the background interplanetary turbulence. We also study the plasma and magnetic transport resulting from the meridional flow and find that deficits of magnetic quantities do occur near the ecliptic. While the effect is relatively small, it is in general agreement with the most recent analysis of 'flux deficit' in the outer heliosphere.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 98; A8; p. 13,233-13,246.
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