Three-dimensional simulations of turbulent spectra in the local interstellar medium

D. Shaikh (1) , G. P. Zank (1)

1 IGPP - Institute of Geophysics and Planetary Physics [Los Angeles]

Three-dimensional time dependent numerical simulations of compressible magnetohydrodynamic fluids describing super-Alfvénic, supersonic and strongly magnetized space and laboratory plasmas show a nonlinear relaxation towards a state of near incompressibility. The latter is characterized essentially by a subsonic turbulent Mach number. This transition is mediated dynamically by disparate spectral energy dissipation rates in compressible magnetosonic and shear Alfvénic modes. Nonlinear cascades lead to super-Alfvénic turbulent motions decaying to a sub-Alfvénic regime that couples weakly with (magneto)acoustic cascades. Consequently, the supersonic plasma motion is transformed into highly subsonic motion and density fluctuations experience a passive convection. This model provides a self-consistent explaination of the ubiquitous nature of incompressible magnetoplasma fluctuations in the solar wind and the interstellar medium.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Sciences de la Terre

D. Shaikh, G. P. Zank. Three-dimensional simulations of turbulent spectra in the local interstellar medium. Nonlinear Processes in Geophysics, 2007, 14 (4), pp.351-359. ⟨hal-00302875⟩