Energy Dissipation in Magnetic Islands Formed during Magnetic Reconnection

Abstract

Abstract Magnetic reconnection converts magnetic energy into particle kinetic energy, and satellite observations have shown that 20%–50% of magnetic energy is channeled into electron kinetic energy. How such a large amount of magnetic energy is dissipated into electron kinetic energy is in debate. In this paper, by performing a large-scale 2D particle-in-cell simulation of magnetic reconnection with a guide field, we find that there exist both ion and electron shear flows in magnetic islands formed during magnetic reconnection, which are unstable to the ion and electron Kelvin–Helmholtz (K-H) instabilities. With the development of the K-H instabilities, the magnetic field lines are twisted in these magnetic islands, and intensified electron-scale current sheets are consequently generated. We quantitatively analyze the energy dissipation during such a process in magnetic islands and find that electrons obtain kinetic energy from the magnetic field while ion kinetic energy is transferred into magnetic energy. At last, it results that about 42% of magnetic energy is dissipated into electron kinetic energy in the whole process of magnetic reconnection. Our results help us better understand why a large amount of magnetic energy can be dissipated into electron kinetic energy.