Alpha-model MHD computation

P.D. MININNI, D.C. MONTGOMERY, Y A. POUQUET

Savannah, Estados Unidos

Congreso; 46th Annual Meeting of the Division of Plasma Physics, American Physical Society; 2004

APS

Magnetohydrodynamic (MHD) turbulent computations with wide spatial-scale separations often demand more spatial resolution than is available or affordable. The "alpha model´´ of D. Holm and colleagues has shown some success in computing realistic large-scale behavior of Navier-Stokes fluids by systematically suppressing the small scales. Here, we report an extension of the alpha model to MHD. Three well-known two-dimensional MHD turbulent phenomena have been computed both with full MHD and with alpha model MHD starting from identical initial conditions, in regimes where full MHD computation is possible. Long wavelength components of the spectra are well reproduced by the alpha model at greatly reduced resolution. However, individual phase-dependent features, such as the locations of configuration-space structures, are not accurately tracked. We also present results for a direct cascade situation that lies outside presently resolvable regimes for full MHD computation, to see what power-law energy spectra will result.