Abstract
A three-dimensional reconnection process, which is caused by the magnetic arcade instability, is investigated using numerical simulations. It is found that the aspect ratio (defined as the ratio of the length to the width of the magnetic arcade) is a crucial parameter to control the nonlinear dynamics. When the aspect ratio is rather small, the dynamics is governed by a symmetric mode, and more explosive reconnection happens. In a longer arcade, on the other hand, an undulating three-dimensional activity arises. It suggests that the variety in solar coronal activity may be caused by the differece in arcade shape.
