标题： 对流和演化的一对阿尔芬激波的粒子模拟 显示英文标题

标题： Formation and Evolution of Pair-Alfvén Shocks with PIC Simulations

摘要： 我们考虑在无碰撞电子-正电子等离子体中最近发现的\emph{对-Alfvén激波}。 我们进行了一系列一维和二维的粒子模拟，以确定这种激波的稳定条件以及维持其增长的机制。 在我们之前的模拟基础上，这些模拟已经表明，这些激波最初是由 Weibel 不稳定性介导的，之后变为阿尔芬型，我们证明激波由自生成的阿尔芬波维持，在上游等离子体中超越激波。 因此，只有当引导磁场强度，从而阿尔芬速度足够小时，增长才可能发生，$\omega_c \lesssim 0.4$（在归一化单位下）。 此外，上游波的产生依赖于阿尔芬波模式与等离子体中的热噪声之间的共振，这在高磁化情况下会被抑制。 这解释了之前识别出的此类激波的条件性缺失。 显示英文摘要

摘要： We consider the recently discovered \emph{pair-Alfv\'en shock wave} occurring in collisionless electron-positron plasmas. We perform a series of Particle-In-Cell studies in one and two dimensions in order to determine the stability conditions for such a shock and the mechanisms which sustain its growth. Building on our previous simulations, which established that these shocks are initially mediated by the Weibel instability before becoming Alfv\'enic, we demonstrate that the shock is sustained by self-generated Alfv\'en waves overtaking the shock in the upstream plasma. As a result growth is only possible when the guiding magnetic field strength, and hence Alfv\'en speed, is sufficiently small, $\omega_c \lesssim 0.4$ (in normalized units). Furthermore the production of the waves in the upstream is dependent on a resonance between the Alfv\'en wave mode and the thermal noise in the plasma, which is inhibited at high magnetization. This explains the conditional absence of this type of shock identified previously.