Session UO1 - Reconnection, Nonlinear Phenomena, and Turbulence.
ORAL session, Thursday morning, October 26
Room 301AB, Qu\'{e}bec City Convention Centre
Two dimensional numerical simulations are used to investigate nonlinear aspects of forced magnetic reconnection in a low beta highly conducting plasma. This is representative of the solar corona, where reconnection may be induced by external perturbations, for example at the photospheric boundary of the corona. The aim is to investigate the energy dissipation by the reconnection, which may provide a mechanism for heating the coronal plasma. The field is taken to be initially a sheared force-free equilibrium in a slab, and the effects of applying a slow deformation to the boundaries are investigated. Previous analytical studies assuming small departures from the initial equilibrium have found that a current sheet forms during an initial ideal phase of evolution, which subsequently relaxes to a reconnected equilibrium, releasing some magnetic energy. The linear theory predicts that the energy release has a singularity when the field is marginally stable to the tearing mode. The nonlinear evolution of the field is calculated numerically, focusing on the energy release. In particular, the strongly nonlinear behavior is studied in the parameter regime in which the linear theory breaks down. It is found that nonlinearities become strong close the marginal stability point, and that beyond this point an explosive energy relaxation, which can release greater energy compared with the pure tearing instability, indeed happens even for weak boundary deformations.