Wan Weigang, Lapenta Giovanni
Center for Plasma Self-Organization and Plasma Theory, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Phys Rev Lett. 2008 Jan 25;100(3):035004. doi: 10.1103/PhysRevLett.100.035004. Epub 2008 Jan 24.
The collisionless island coalescence process is studied with particle-in-cell simulations, as an internal-driven magnetic self-organization scenario. The macroscopic relaxation time, corresponding to the total time required for the coalescence to complete, is found to depend crucially on the scale of the system. For small-scale systems, where the macroscopic scales and the dissipation scales are more tightly coupled, the relaxation time is independent of the strength of the internal driving force: the small-scale processes of magnetic reconnection adjust to the amount of the initial magnetic flux to be reconnected, indicating that at the microscopic scales reconnection is enslaved by the macroscopic drive. However, for large-scale systems, where the micro-macro scale separation is larger, the relaxation time becomes dependent on the driving force.
采用粒子模拟研究了无碰撞岛屿合并过程，将其作为一种内部驱动的磁自组织情形。发现对应于合并完成所需总时间的宏观弛豫时间关键取决于系统的尺度。对于小尺度系统，宏观尺度和耗散尺度耦合更紧密，弛豫时间与内部驱动力的强度无关：磁重联的小尺度过程会根据待重联的初始磁通量大小进行调整，这表明在微观尺度上重联受宏观驱动的支配。然而，对于大尺度系统，微观与宏观尺度分离较大，弛豫时间则取决于驱动力。
