Release of magnetic energy in asymmetrical quadrupolar force-free fields

Using a two-dimensional, three-component dissipative MHD model we numerically simulated the process of magnetic energy release in a local asymmetrical quadrupolar force-free field with a high current layer. The results show that the process can be divided into two stages, first, anomalous resistive dissipation in the high current layer heats up the plasma in the layer to 3×10⁶K, forming a hot ring; next, triggered by the dissipation, the current in the magnetic separation surface rises rapidly and erupts into anomalous resistive dissipation and field reconnection. The main energy release takes place at the magnetic separation line and the separation surface in the high-shear force-free field, with the plasma temperature as high as 1.9×10⁷K. This process of triggered energy release may be an important mechanism of solar flares.