We study with a two-dimensional particle-in-cell simulation the stability of a discontinuity or piston, which separates an electron-positron cloud from a cooler electron-proton plasma. Such a piston might be present in the relativistic jets of accreting black holes separating the jet material from the surrounding ambient plasma and when pair clouds form during an X-ray flare and expand into the plasma of the accretion disk corona. We inject a pair plasma at a simulation boundary with a mildly relativistic temperature and mean speed. It flows across a spatially uniform electron-proton plasma, which is permeated by a background magnetic field. The magnetic field is aligned with one simulation direction and oriented orthogonally to the mean velocity vector of the pair cloud. The expanding pair cloud expels the magnetic field and piles it up at its front. It is amplified to a value large enough to trap ambient electrons. The current of the trapped electrons, which are carried with the expanding cloud front, drives an electric field that accelerates protons. A solitary wave grows and changes into a piston after it saturated. Our simulations show that this piston undergoes a collision-less instability similar to a Rayleigh-Taylor instability. The undular mode grows and we observe fingers in the proton density distribution. The effect of the instability is to deform the piston but it cannot destroy it.

中文翻译：

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热对等离子体和电子-质子等离子体之间边界的无碰撞瑞利-泰勒不稳定性：波状模式

我们使用二维粒子胞内模拟研究了不连续性或活塞的稳定性，它将电子 - 正电子云与较冷的电子 - 质子等离子体分开。这样的活塞可能存在于吸积黑洞的相对论射流中，将射流物质与周围的环境等离子体分开，并且当在 X 射线耀斑期间形成对云并扩展到吸积盘日冕的等离子体中时。我们在具有温和相对论温度和平均速度的模拟边界处注入一对等离子体。它流过空间均匀的电子-质子等离子体，该等离子体被背景磁场所渗透。磁场与一个模拟方向对齐，并与一对云的平均速度矢量正交。膨胀的对云驱逐磁场并将其堆积在它的前面。它被放大到足以捕获环境电子的值。被俘获电子的电流随着不断扩大的云锋携带，驱动一个加速质子的电场。孤立波在饱和后会增长并变成活塞。我们的模拟表明，该活塞经历了类似于瑞利-泰勒不稳定性的无碰撞不稳定性。波状模式增长，我们在质子密度分布中观察到手指。不稳定的效果是使活塞变形，但不能破坏它。孤立波在饱和后会增长并变成活塞。我们的模拟表明，该活塞经历了类似于瑞利-泰勒不稳定性的无碰撞不稳定性。波状模式增长，我们在质子密度分布中观察到手指。不稳定的效果是使活塞变形，但不能破坏它。孤立波在饱和后会增长并变成活塞。我们的模拟表明，该活塞经历了类似于瑞利-泰勒不稳定性的无碰撞不稳定性。波状模式增长，我们在质子密度分布中观察到手指。不稳定的效果是使活塞变形，但不能破坏它。