Dynamical behavior of thin current sheets controlled by collisionless reconnection in the presence of plasma inflow and outflow through the boundary is investigated by using newly developed electromagnetic (EM) particle simulation codes. It is found from 2D EM particle simulation that there are two evolving regimes in the temporal behavior of collisionless reconnection, dependently on the window size of plasma inflow, i.e., a steady regime and an intermittent regime [1,2]. The steady collisionless reconnection is realized in the case of small input window size, in which the reconnection rate is balanced with the flux input rate at the upstream boundary and the global dynamic process of magnetic reconnection is dominantly controlled by ion dynamics [3]. As the window size increases, the current sheet becomes longer, which is favorable to the excitation of an electron tearing instability. The system evolves into an intermittent regime, in which magnetic islands are frequently generated in the current sheet.
In three-dimensional case the spatial structure of current sheet is dynamically modified by plasma instabilities excited through wave-particle interaction. The lower hybrid drift instability (LHDI) is observed to grow in the periphery of current layer in an early period, while a drift-kink instability (DKI) is triggered at the neutral sheet as a second instability after the current sheet is modified through nonlinear evolution of the LHDI and its width becomes less than ion Larmor radius[1,4]. It is also found that local island structures of plasmas that are generated by tearing instability in the central current sheet move to grow in the downstream, and suffer from the kink-like instability after the current accumulation inside the islands [5].

References