A TRIGGER MECHANISM OF MAGNETIC RECONNECTION AND PARTICLE ACCELERATION DURING THINNING OF THE CURRENT SHEET

摘要

One of the trigger mechanisms of magnetic reconnection in the compressing current sheet is studied by using a two-dimensional full particle-in-cell code modified from the TRISTAN code. In the compressed current sheet, the electrons are heated preferentially perpendicular to the magnetic field due to adiabatic heating. The thinning and anisotropy T_⊥/T_‖ of electrons in the current sheet vigorously enhance the tearing instability with several small-scale magnetic islands. The generated magnetic islands successively coalesce and the magnetic energy is converted into plasma kinetic energy. Through the coalescence, high-energy electrons are quasi-periodically produced. At almost the same time, some ions are accelerated by the magnetosonic shock waves generated around the current sheet. The acceleration sites for the ions move the outside of the current sheet. At the final stage, all magnetic islands merge into a large one whose width is about 10 times larger than the compressed sheet width. The thinning of the current sheet leads to the generation of large-scale magnetic islands and converts the magnetic field energy into kinetic energy of the plasma. The dynamical evolution of current sheets can be applied to solar flares.