AI 中文总结
该研究通过长时间二维三分量粒子模拟，在特定坐标系下研究无磁化相对论性电子 - 正电子对激波，发现激波接近稳态，下游稳态取决于上游温度，费米型加速能量受限，下游磁场有类孤子结构。
AI 中文摘要
我们展示了一系列在前共动坐标系中对无磁化相对论性电子 - 正电子对激波进行的前所未有的长时间二维三分量粒子模拟。通过在下游实施移动壁边界条件并在上游边界连续注入，维持固定模拟域大小以进行更长时间模拟。最长模拟超过100000个等离子体频率倒数，远超先前发表的模拟时长。通过多样模拟发现激波接近渐近、与时间无关状态。下游稳态仅取决于注入边界的上游温度，上游前驱演化较慢且依赖上游长度。还发现费米型加速能量受限，下游磁场有类孤子结构，磁畴独立演化。
英文摘要
We present a series of unprecedently long 2D3V PIC simulations of unmagnetized relativistic $e^{-}e^{+}$-pair shocks performed in a front-comoving frame. By implementing a moving-wall boundary condition in the downstream together with continuous injection at the upstream boundary, we maintain a fixed simulation domain size, opening the way to perform substantially longer simulations. Our longest runs extend beyond $100000\,ω_p^{-1}$, exceeding the duration of the previously published simulations by a factor of several. Across a diverse set of simulations -- varying upstream/downstream lengths, transverse sizes, and particle-per-cell counts -- we find strong evidence that the shock approaches an asymptotic, time-independent state. In the downstream region, the steady state depends only on the upstream temperature at the injection boundary and does not depend on a particular numerical realization. The upstream precursor evolves slower and retains a dependence on the simulation's upstream length, that may be of minor observational consequence, since radiation from astrophysical shocks predominantly originates from the downstream region. We also find that Fermi-type acceleration is limited in energy and a true power-law tail never forms. Another important finding is that the downstream magnetic field has a soliton-like structure, where individual magnetic domains evolve independently, each comprising a compact, highly magnetized core embedded within an extended, weakly magnetized region. The magnetic-field distribution around the centers of these spots has approximately Lorentzian profile.
Comments16 pages, 12 figures
