HR: 0830h
AN: SH21B-0131    [PDF]
TI: Whistler wave turbulence in astrophysical plasmas
AU: * McKenzie, J
AF: Institute of Geophysics and Planetary Physics (IGPP), University of California, Riverside, CA 92521 United States
AU: Dastgeer, S
EM: dastgeer@citrus.ucr.edu
AF: Institute of Geophysics and Planetary Physics (IGPP), University of California, Riverside, CA 92521 United States
AU: Zank, G
AF: Institute of Geophysics and Planetary Physics (IGPP), University of California, Riverside, CA 92521 United States
AB: In certain circumstances, astrophysical and laboratory plasmas are characterized by time and spatial length scales that are relatively fast and small compared to ion gyro-periods and gyro-radii which can not be explained by magnetohydrodynamical (MHD) description of plasmas (accruing on Alfven transit time). A theory best suited for describing rapid electron time scale phenomena is known as electron magnetohydrodynamics (EMHD) in which Whistler waves are the characteristic modes propagating along a self-consistent or mean magnetic field. Whistler waves and electron dynamics are critical to many aspects of astrophysical plasmas, such as the structure of collisionless quasi-perpendicular shocks, to our understanding of magnetic reconnection, dissipation and heating processes in the solar wind, fast plasma opening switches, anomalous diffusion of field in plasma, and others. In this work, we investigate spectral transfer processes in the presence of a self-consistent or mean magnetic field in a two dimensional EMHD model. Our investigation, based upon fluid simulations, reveal that an initially isotropic turbulent spectrum evolves into an anisotropic spectrum in the presence of a mean magnetic field. The anisotropy varies systematically with the strength of the external magnetic field. A particularly simple relationship between the anisotropy of the turbulence and the external mean magnetic field emerges from the simulations. We find that the anisotropic cascades in the EMHD turbulence acquire an almost linear relationship with the magnitude of the external magnetic field. Based on weak turbulence theory, we confirm that the whistler waves mediate anisotropic cascades by suppressing the spectral transfer in their direction of propagation.
DE: 2149 MHD waves and turbulence
DE: 2164 Solar wind plasma
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting