Satellite Observations And Full Particle Simulations Of Multiple X Line Magnetic Reconnection

Magnetic reconnection,widely spread in universe and experimental plasma,is a physical process in highly conducting plasmas in which the magnetic topology is rearranged and magnetic energy is converted to kinetic energy, thermal energy.Many explosive space plasma phenomena related to magnetic reconnection, such as, solar flares, magnetospheric substorms. Over the past decades, the satellite observations provided the evidence of collisionless reconnection in magnetosphere, We study on the structure of multiple X line collisionless reconnection and mechanism of high energy electrons,which are based on the Cluster satellite and full particle simulation.The main contents are as follows:As is well known,magnetic reconnection has long been believed to be an efficient engine for energetic electrons production. Four different structures have been proposed for electrons being energized: flux pileup region, density cavity located around the separatrix, magnetic island and thin current sheet. We used the flux ratio between the energetic electrons(> 50 ke V) and lower energy electrons(<26 ke V) to quantify the electron acceleration efficiency. We do not find any specific sequence in which electrons are accelerated within these structures,though the flux pileup region, magnetic island and thin current sheet have higher probabilities to reach the maximum efficiency among the four structures than the density cavity.However, the most efficient electron energization usually occurs outside these structures. Our results could provide important constraints for the further modeling of electron acceleration during magnetic reconnection.We will study the coalescence physical process of multiple X line reconnection in the guide field. The magnetic island structures are formed of multiple X line reconnection. When there are many magnetic islands formed in the reconnection, the magnetic island are easily coalescence between two neighboring.Meanwhile, we will focus on the behavior of the inflow or outflow of particle,and out-of-the plane of jy,Hall electric field and magnetic field, especially the behavior characteristic of electrons, and clear explicitly reconnection electric field in the merging point sources by analyzing the generalized Ohm's law. Finally,we conclude that the coalescence of primary magnetic island is symmetry, but the coalescence of secondary island is asymmetry.