SPONTANEOUS RECONNECTION OF LINE-TIED FLUX TUBES

A model is presented, for spontaneous reconnection of coronal magnetic fields subject to axial line-tying. An initial equilibrium representi ng multiple flux tubes of alternating helicity is shown to be linearly unstable to a line-tied generalization of island coalescence. Numeric al time-dependent simulations of the nonlinear evolution of this syste m reveal the rapid ideal development of intense current layers between current tubes with the same sign of helicity. The flow which arises f rom this stage leads to equally rapid dissipation of the current layer . This is accompanied by reconnection as it can be defined for three-d imensional line-tied fields. The current layers form at the ''top'' of the flux tubes, away from the line-tied ends. In this region the reco nnection very much resembles the resistive phase of two-dimensional co alescence. The structure of the current layer near the line-tied ends hints at a generalization of current-sheet theories to three dimension s. Reconnection can liberate more than 20% of the free magnetic energy in the initial equilibrium.