  The sudden reconnection of a non-force free 2D current layer, embedded in a
low-beta plasma, triggered by the onset of an anomalous resistivity, is studied
in detail. The resulting behaviour consists of two main phases. Firstly, a
transient reconnection phase, in which the current in the layer is rapidly
dispersed and some flux is reconnected. This dispersal of current launches a
family of small amplitude magnetic and plasma perturbations, which propagate
away from the null at the local fast and slow magnetosonic speeds. The vast
majority of the magnetic energy released in this phase goes into internal
energy of the plasma, and only a tiny amount is converted into kinetic energy.
In the wake of the outwards propagating pulses, an imbalance of Lorentz and
pressure forces creates a stagnation flow which drives a regime of impulsive
bursty reconnection, in which fast reconnection is turned on and off in a
turbulent manner as the current density exceeds and falls below a critical
value. During this phase, the null current density is continuously built up
above a certain critical level, then dissipated very rapidly, and built up
again, in a stochastic manner. Interestingly, the magnetic energy converted
during this quasi-steady phase is greater than that converted during the
initial transient reconnection phase. Again essentially all the energy
converted during this phase goes directly to internal energy. These results are
of potential importance for solar flares and coronal heating, and set a
conceptually important reference for future 3D studies.
