磁场重联的二维粒子模拟研究

TWO-DIMENSIONAL PARTICLE SIMULATION STUDY OF MAGNETIC RECONNECTION

利用二维全粒子模拟方法研究了无碰撞等离子体中的磁场重联过程,得到了不同区域的离子和电子速度分布。计算结果表明,电子和离子在扩散区中的不同动力学特性产生的Hall电流使磁场的y分量B_y呈现四极形分布。离子和电子的速度分布偏离了初态时的Maxwell分布,呈现非局域的多重分布。同时由于磁场重联而产生的电场使电子在X点附近得到加速和加热,因而在电子的能谱分布中形成一高能尾。

The process of magnetic reconnection in the collisionless plasma and distributions of particles in different positions are studied based on two-dimensional particle simulation. It is found that the procedure of the magnetic reconnection saturates at t=14.8 after a phase of linear growth, and the difference between the ion and electron dynamics in the diffusion region gives rise to in-plane (Hall) currents, which produces an out-of-plane By field with a quadrupolar structure. The velocity distributions of ion and electron deviate from the initial Maxwell distribution and are characterized by non-local multi-component distributions with high anisotropy, which is consistent with the observations of Seon and Onsager. At the same time the electron acceleration and heating take place near the X-type region, so the electron distribution shows a high-energy tail in the electron energy distribution. At last, we find that outgoing flux velocity of the electrons near the X point is higher than that of the ions. The flux velocity of the electrons is about 2 Alfven speed, while the flux velocity of the ions is about 1 Alfven speed.