HR: 0800h
AN: SH51C-0283    [Abstracts]
TI: Spectral Maps of Collisionless-MHD Turbulence in $k{_\parallel}$-$k_{\perp}$ Space
AU: * Borovsky, J E
EM: jborovsky@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D466, Los Alamos, NM 87545 United States
AU: Gary, S P
EM: pgary@lanl.gov
AF: Los Alamos National Laboratory, Mail Stop D466, Los Alamos, NM 87545 United States
AB: For turbulence in fluids, the energy cascade is famously depicted by a one-dimensional (omnidirectional) wavenumber spectrum that is divided into three regions: an energy subrange at small k, an inertial subrange at intermediate k, and a dissipation subrange at large $k$. Eddy-eddy interactions produce a net flow of energy from small-$k$ to large-$k$. For turbulence in collisionless plasmas, the magnetic field ${\vec B}$ of the plasma defines a coordiante system with behavior parallel to${\vec B}$ differing from behavior perpendicular to ${\vec B}$. A map of MHD turbulence in $k_\parallel$-$k_\perp$ space is considered. Owing to the magnetic field, every turbulent fluctuation in a plasma has an eddy nature and an Alfven-wave nature. The wave nature of the fluctuations has two major effects. First, the wave nature splits the inertial subrange into two regions in $k_\parallel$-$k_\perp$ space: a region where eddy-eddy interactions happen more quickly than Alfven-wave effects (the Kolmogorov-turbulence region at $k_\perp$ $\gg$ $k_\parallel$) and a region where eddy-eddy interactions happen more slowly than Alfven-wave effects (the Kraichnan-turbulence region at $k_\perp$ $\ll$ $k_\parallel$). Second, the wave nature of the fluctuations allows wave-particle interactions to dissipate the turbulence. The boundary ("inner scale") between the inertial subrange and the dissipation subrange is a curve in $k_\parallel$-$k_\perp$ space that depends on where electron Landau damping, ion Landau damping, or ion cyclotron damping dominates over eddy-eddy energy transfer, which differs for left-hand-polarized (Alfven-cyclotron branch) and right-hand-polarized (magnetosonic-whister branch) turbulent fluctuations. For solar-wind turbulence, the two $k_\parallel$-$k_\perp$ maps are drawn: one for the left-hand fluctuations in the turbulence and one for the right-hand fluctuations in the turbulence.
DE: 7863 Turbulence
DE: 7867 Wave/particle interactions
DE: 2149 MHD waves and turbulence
DE: 2159 Plasma waves and turbulence
DE: 2164 Solar wind plasma
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting