Liu Yi-Hsin, Guo Fan, Daughton William, Li Hui, Hesse Michael
NASA-Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev Lett. 2015 Mar 6;114(9):095002. doi: 10.1103/PhysRevLett.114.095002. Epub 2015 Mar 3.
Using fully kinetic simulations, we study the scaling of the inflow speed of collisionless magnetic reconnection in electron-positron plasmas from the nonrelativistic to ultrarelativistic limit. In the antiparallel configuration, the inflow speed increases with the upstream magnetization parameter σ and approaches the speed of light when σ>O(100), leading to an enhanced reconnection rate. In all regimes, the divergence of the pressure tensor is the dominant term responsible for breaking the frozen-in condition at the x line. The observed scaling agrees well with a simple model that accounts for the Lorentz contraction of the plasma passing through the diffusion region. The results demonstrate that the aspect ratio of the diffusion region, modified by the compression factor of proper density, remains ∼0.1 in both the nonrelativistic and relativistic limits.
通过全动力学模拟，我们研究了电子 - 正电子等离子体中无碰撞磁重联流入速度从非相对论极限到超相对论极限的标度关系。在反平行构型中，流入速度随上游磁化参数σ增加，当σ > O(100)时接近光速，导致重联率增强。在所有情况下，压力张量的散度是在x线处打破冻结条件的主导项。观测到的标度关系与一个简单模型吻合良好，该模型考虑了通过扩散区域的等离子体的洛伦兹收缩。结果表明，在非相对论和相对论极限下，由适当密度压缩因子修正的扩散区域的纵横比均保持在~0.1。
