Electron Acceleration in a Dynamically Evolved Current Sheet of Solar Coronal Conditions

Electron acceleration in a drastically evolved current sheet of solar coronal conditions is investigated via the combined resistive Magnetohydrodynamics (MHD) and test particle approaches. With high magnetic Reynolds number, the long-thin current sheet is tearing into a chain of magnetic islands, which grow in size and coalesce together. The acceleration of electrons are explored in three typical evolvement phases: when several large magnetic islands are formed (phase1), two of them are approaching each other (phase2) and almost merging into a "monster" magnetic island (phase3). The results show that for all the three phases electrons with an initially Maxwellian distribution evolve into a heavy-tailed distribution and more than 20% of the electrons can be accelerated higher than 200 keV within 0.1 second and some of them can even be energized up to MeV ranges. Most of the energetic electrons move around the magnetic islands in clockwise direction (anti-parallel to the magnetic field lines), drifting in the -Z direction. The energetic electrons with 10 keV < Ek < 200 keV are located outside the magnetic separatrices, where parallel electric field (Ep) is small. The electrons with 200 keV < Ek < 5000 keV are distributed inside the magnetic islands where Ep is moderate large but have complex structures. The electrons with Ek > 5000 keV are located around the outer regions of the magnetic islands or at the core regions of the magnetic islands. Some of the most energetic electrons even appear in the small secondary magnetic islands that are embedded in the diusion regions in between the magnetic islands. It is the trapping eect of the magnetic islands and the distributions of Ep that determine the acceleration processes and space distribution of the energetic electrons.