HR: 14:10h
AN: SH13B-03    [Abstracts]
TI: Reduced MHD and Shell-Model Simulations of Coronal Heating in Magnetized Loops: Scaling Laws.
AU: * Velli, M
EM: velli@arcetri.astro.it
AF: Dipartimento di Astronomia, Universit… di Firenze, Largo E. Fermi 2, Firenze, FI 50125 Italy
AU: * Velli, M
EM: velli@arcetri.astro.it
AF: Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 United States
AU: Rappazzo, F
EM: rappazzo@df.unipi.it
AF: Dipartimento di Fisica, Universit… di Pisa, Largo B. Pontecorvo, Pisa, PI 56100 Italy
AU: Buchlin, E
EM: eric@arcetri.astro.it
AF: Dipartimento di Astronomia, Universit… di Firenze, Largo E. Fermi 2, Firenze, FI 50125 Italy
AU: Einaudi, G
EM: einaudi@df.unipi.it
AF: Dipartimento di Fisica, Universit… di Pisa, Largo B. Pontecorvo, Pisa, PI 56100 Italy
AB: We present direct magnetohydrodynamic (MHD) simulations modeling the heating of coronal loops in the solar atmosphere via the tangling of coronal field lines by photospheric footpoint motions within the framework of reduced MHD. We carry out long-time 3D simulations with the highest resolutions to date and compare them to simpler shell-model simulations, in which the non-linear couplings in wave-number space are drastically simplified. The latter reach much larger Reynolds numbers but can not describe the dynamics in physical space, which is driven by the reconnection of induced coronal magnetic fields. In the direct numerical simulations, we reach resolutions sufficient to derive scaling properties with Reynolds numbers, loop length, and ratio of photospheric velocity to coronal Alfv‚n speeds. Line-tying of the axial field lines plays a significant role by inhibiting coalescence and inverse cascades in the loop cross-sections, which dominate dynamics in 2D models. To examine the role of line-tying simulations including gradients in the density from the photosphere to the corona are also included. Shell-model calculations are carried out for much longer time-scales, sufficient to calculate the statistical properties of heating. The scaling properties derived from the shell models and from reduced MHD are compared and contrasted and on this basis we discuss the required role of emerging flux, neglected here, in coronal heating.
DE: 7509 Corona
DE: 7519 Flares
DE: 7524 Magnetic fields
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005