Session UP2 - Poster Session: Supplemental/Postdeadline Abstracts.
POSTER session, Friday morning, November 19
Fifth Avenue, The Westin Seattle
Three-dimensional (3D) nonlinear dynamics of the solar coronal magnetic arcades, to which the magnetic helicity is constantly injected by a shearing motion on the feet, is investigated based on the magnetohydrodynamic numerical simulation.
The simulation shows us that, as a result of the helicity injection, the magnetic arcade instability grows up and releases the free energy supplied by the boundary motion. Just a single Fourier mode dominates the instability, and the mode number of that switches from zero to a positive number when the arcade length increases about ten times larger than the width. Therefore, 3D behavior comes up in the long arcade system, while, in relatively short arcades, the dynamics is much similar to the two dimensional (2D) model. The instability creates the current sheet above each arcade, and drives magnetic reconnection in any cases. In long arcade system, however, the current sheet appears only in some part of the arcade top, and the reconnection site travels along arcade axis. Therefore, the energy relaxation in the long arcades is much continuous compared to the intermittent activity shown in the 2D system.
Furthermore, we numerically analyze the liner stability of the equilibrium component extracted from the nonlinear simulation, and reveal that multiple number of unstable modes always exist. These results suggest that the dominant mode could be spontaneously selected by some nonlinear mechanism.
The copy of poster presentation will be uploaded in http://plasma.sci.hiroshima-u.ac.jp/\~ kusano/DPP99/.