Ion dynamics in steady collisionless driven reconnection

Improvement of the Multi-Hierarchy Simulation Model Based on the Real-Space Decomposition Method

Multi-hierarchy simulation models aimed at analysis of magnetic reconnection were developed. Based on the real-space decomposition method, the simulation domain consists of three parts: a magnetohydrodynamics (MHD) domain, a particle-in-cell (PIC) domain, and an interface domain to communicate MHD and PIC data. In this paper, the previous model (the 1D interlocking with the upstream condition) by the authors is improved to three types of new models, i.e., two types of the 1D interlocking with the downstream condition and one type of the 2D interlocking with the upstream condition. For their verification, simulations of plasma propagation across the multiple domains were performed in the multi-hierarchy models, and it was confirmed that the new interlocking methods are physically correct.

Observation of ion acceleration and heating during collisionless magnetic reconnection in a laboratory plasma

The ion dynamics in a collisionless magnetic reconnection layer are studied in a laboratory plasma. The measured in-plane plasma potential profile, which is established by electrons accelerated around the electron diffusion region, shows a saddle-shaped structure that is wider and deeper towards the outflow direction. This potential structure ballistically accelerates ions near the separatrices toward the outflow direction. Ions are heated as they travel into the high-pressure downstream region.

Suppression of Hall-term effects by gyroviscous cancellation in steady collisionless magnetic reconnection

The formation of an ion-dissipation region, in which motions of electrons and ions decouple and fast magnetic reconnection occurs, is demonstrated during a steady state of two-dimensional collisionless driven reconnection by means of full-particle simulations. The Hall-term effect is suppressed due to the gyroviscous cancellation at scales between the ion-skin depth and ion-meandering-orbit scale, and thus ions are tied to the magnetic field. The ion frozen-in constraint is strongly broken by nongyrotropic pressure tensor effects due to ion-meandering motion, and thus the ion-dissipation region is formed at scales below the ion-meandering-orbit scale. A similar process is observed in the formation of an electron-dissipation region. These two dissipation regions are clearly observed in an out-of-plane current density profile.