Triggered Magnetic Energy Release in Solar Flares

Abstract

A numerical simulation is presented in this paper in terms of a two-dimensional, dissipative MHD model, concerning the magnetic energy release of a local quadrupolar force-free field with a high current layer. It is assumed that anomalous resistive dissipation occurs when electric current density exceeds a certain critical value. The magnetic energy release obtained is largely divided into two stages. The first stage lasts 1-2 minutes, characterized by anomalous resistive dissipation in the high current layer. As a result, the plasma in that layer is heated to 2 × 10<SUP>6</SUP> K, B<SUB>z</SUB> (the shear component of the magnetic field) decreases, and the magnetic field lines descend there. The descending field lines squeeze the separatrix below and cause a growth of current on it. When the current density exceeds the critical value, the second stage begins: anomalous resistive dissipation and magnetic reconnection take place across the separatrix and convert magnetic energy into thermal energy. Such a process proceeds in a chain manner, and the maximum temperature in the separatrix reaches 1.8 × 10<SUP>7</SUP> K in less than 10 minutes. The anomalous resistive dissipation in the high current layer in the first stage plays the role of trigger for the magnetic energy release of the force-free field in the second stage. We suggest that this is a possible mechanism for magnetic energy release associated with solar flares.