Towards cross-hierarchy simulation of collisionless driven reconnection in an open system

The basic idea of a cross-hierarchy model for magnetic reconnection in an open system is proposed, where a microscopic system is surrounded by a macroscopic system and the interaction between the two systems is expressed by the plasma inflow and outflow through the system boundary. Collisionless driven reconnection in two-dimensional and three-dimensional open systems is demonstrated using an open particle simulation model developed as a microscopic part of a cross-hierarchy model. It is found that the openness of the system and scale-coupling effects play crucial roles in collisionless driven reconnection

Structure formation and dynamical behavior of kinetic plasmas controlled by magnetic reconnection

Structure formation and dynamical behavior of kinetic plasmas controlled by magnetic reconnection is investigated by means of electromagnetic particle simulations. Two-dimensional simulation in a long time scale reveals that there are two evolving regimes in the temporal behavior of current layer structure, dependently on the spatial size of plasma inflow through the upstream boundary, i.e., a steady regime and an intermittent regime. In three-dimensional case the spatial structure of current sheet is dynamically modified by plasma instabilities excited through wave-particle interaction

Three-dimensional particle simulation on structure formation and plasma instabilities in collisionless driven reconnection

Structure formation and plasma instabilities in collisionless driven reconnection are investigated by three-dimensional electromagnetic (EM) particle simulation in an open system. In the early period, the lower-hybrid drift instability is excited in the periphery of the current layer. In the intermediate period, magnetic islands are created in the downstream due to magnetic reconnection, and they become unstable against a kink instability. In the late period, after the magnetic islands go out through the boundary, a wide, thin current sheet is generated and a low-frequency EM mode is excited in the central region. This mode has a frequency comparable to the ion gyration frequency, and thus it is considered to be the drift kink instability

Two-scale structure of the current layer controlled by meandering motion during steady-state collisionless driven reconnection

A steady two-scale structure of current layer is demonstrated in the collisionless driven reconnections without a guide field by means of two-dimensional full-particle simulations in an open system. The current density profile along the inflow direction consists of two parts. One is a low shoulder controlled by the ion-meandering motion, which is a bouncing motion in a field reversal region. The other is a sharp peak caused mainly by the electron-meandering motion. The shoulder structure is clearly separated from the sharp peak for the case of a large mass ratio calculation mi/m_e = 200 because the ratio of the ion-meandering orbit amplitude to the electron-meandering orbit amplitude is proportional to (mi/m_e)^1/4. Although the ion frozen-in constraint is broken within a distance of the ion skin depth c/omega_pi, the violation due to the ion inertia is weak compared to the strong violation caused by the ion-meandering motion. The violation of the electron frozen-in constraint caused by the electron-meandering motion is stronger than the violation due to the electron inertia, and thus the electron-meandering motion produces the reconnection electric field in the central region where the current has the sharp peak structure