PROMPT PARTICLE-ACCELERATION AND PLASMA-JET FORMATION DURING CURRENT LOOP COALESCENCE IN SOLAR-FLARES

High-energy particle acceleration during current loop coalescence in solar flares is investigated by numerical simulation, using the theoretical model derived by Sakai and Tajima. Simulation results show that both electrons and protons can be quasi-periodically accelerated to relativistic energies within a very short time (≪1s), when the ratio Bp/Bt between the poloidal (Bp is produced by the loop current) and the toroidal (Bt is the potential field) components of the magnetic field is greater than 1. On the other hand, when Bp/Bt < 1, the two current loops begin to rotate around the reconnection point. It is shown that the spiral two-sided plasma jet can be explosively driven by the plasma rotational motion during the two-current loop coalescence process. The acceleration time getting to the maximum jet velocity is quite short and less than 1 s. It is also shown that the rebound following the plasma collapse driven by magnetic pinch effect can strongly induce super-magnetosonic flow, which can generate the fast magnetosonic shock waves.