太阳物理研究组知识库

Electric field induced in magnetic reconnection is an efficient mechanism for generating energetic particles, but the detailed role it plays is still an open question in solar flares. In this work, accelerations of particles in an evolving reconnecting current sheet are investigated via the test-particle approach, and the electromagnetic field is taken in a self-consistent fashion from a 2.5D numerical experiment for the magnetic reconnection process in the corona. The plasma instabilities like the tearing mode in the current sheet produce magnetic islands in the sheet, and island merging occurs as well. For the motion of the magnetic island, it yields the occurrence of the opposite electric field at both endpoints of the island; hence, tracking the accelerated particles around magnetic islands suggests that the parallel acceleration does not apparently impact the energy gain of particles, but the perpendicular acceleration does. Furthermore, our results indicate that the impact of the guide field on the trajectory of accelerated particles in a more realistic electromagnetic configuration works only on those particles that are energetic enough. The energy spectra of both species show a single power-law shape. The higher-energy component of the power-law spectrum results from the particles that are trapped in the current sheet, while the escaped and partly trapped particles contribute to the lower-energy component of the spectrum. The evolution of the spectrum shows a soft-hard-soft pattern that has been observed in flares.