HR: 1340h
AN: NG43A-0556    [Abstracts]
TI: On the Dynamics of Incompressibility in the Solar Wind
AU: * Shaikh, D
EM: dastgeer@ucr.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 United States
AU: Zank, G P
EM: zank@ucr.edu
AF: Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521 United States
AB: Solar wind and insterstellar magnetoplasmas frequently behave as though they are incompressible. This has proved a major challenge to our understanding of small-scale dynamical processes in a plasma. A significant motivation for these studies is the observation of a Kolmogorov-like density spectrum over decades in wavenumber space that appears to pervade the ISM. Why an apparently compressive characteristic of ISM turbulence should behave as though it were a manifestation of incompressible MHD turbulence has yet to be answered conclusively. On the basis of three-dimensional time dependent numerical simulations, we find that compressible magneto hydrodynamic fluids describing super-Alfvénic, supersonic and strongly magnetized space and laboratory plasmas decay progressively to a state of near incompressibility, characterized by a subsonic turbulent Mach number. This transition is mediated dynamically by disparate spectral energy dissipation rates in compressible magnetosonic and shear Alfvénic modes. Dissipation leads to super-Alfvénic turbulent motions decaying to a sub-Alfvénic regime that couples weakly with (magneto)acoustic cascades. Consequently, the supersonic plasma motion dissipates into highly subsonic motion and density fluctuations experience a passive convection.
DE: 2149 MHD waves and turbulence (2752, 6050, 7836)
DE: 2164 Solar wind plasma
DE: 4455 Nonlinear waves, shock waves, solitons (0689, 2487, 3280, 3285, 4275, 6934, 7851, DE: 7599 General or miscellaneous
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
SC: Nonlinear Geophysics [NG]
MN: Fall Meeting 2005