Energy conversion during multiple X-lines reconnection

Magnetic reconnection efficiently converts magnetic energy into kinetic and thermal energy of plasmas. It is recently found that energy conversion mainly occurs at reconnection fronts (characterized by the enhancement of the reconnected magnetic field component B-z) and the reconnection exhaust during single X-line reconnection. However, magnetic islands are produced in multiple X-line reconnection. These islands can coalesce, which complicates the energy conversion process relative to the single X-line reconnection. Using 2.5D particle-in-cell simulation, we examine the energy conversion in multiple X-line reconnection. It is found that the magnetic energy releases predominantly through primary islands and second at X-lines. The contributions of secondary islands and merging current sheets to magnetic energy conversion are much less than those by the primary islands. The presence of the guide field reduces the energy conversion rate but increases the proportion of the electron energy gain. We further find that island coalescence increases the energy conversion in magnetic islands.