HR: 17:45h
AN: SH32D-08    [PDF]
TI: Large Scale Hybrid 2D Simulations of the Relaxation of an Initially Isotropic Spectrum of Alfven Waves
AU: Mangeney, A
EM: mangeney@despace.obspm.fr
AF: Observatoire de Paris, LESIA, Place Jules Janssen, Meudon, 92195 France
AU: * Travnicek, P
EM: trav@alenka.ufa.cas.cz
AF: Institute of Atmospheric Physics, Academy of Sciences of the Czech Republic, Bocni II/1401, Prague, 14131 Czech Republic
AB: In many situations observed in space plasmas, large MHD scales are believed to act as reservoir for a nonlinear cascade, bringing fluctuation energy to scales where kinetic processes (Landau or cyclotron resonnances) can transform them into thermal energy. These kinetic processes operate at smaller spatial scales and more rapid time scales, so that a numerical simulation describing both the nonlinear cascade and the kinetic processes were, untill recently, out of reach. The rapid increase of computing efficiency allows now to study the competition between these two processes in more realistic simulations. We present here 2D hybrid simulations (the protons are treated as particles and the electrons as a massless fluids) of the relaxation of an initially isotropic spectrum of Alfven waves. The dimensions achieved in these simulations can be as high as 1000x1000 cells in phsysical space ( and 1000 particles per cell), with a resolution of a few tenth of proton inertial lentgh (the electric resistivity being chosen so that the "magnetic Reynolds" number is of the order of 50-100). By changing the plasma beta and the typical wavelength of the initial perturbations, we vary the relative efficiency of the cascade processes and the cyclotron absorption. The results shows a subtle interplay between these two processes, which depend on the initial level of fluctuations (which fixes the nonlinear overturning time). We shall also discuss the relvance of these simulations for the heating of the outer corona and solar wind.
DE: 2164 Solar wind plasma
DE: 2752 MHD waves and instabilities
DE: 2753 Numerical modeling
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting