Particle-in-cell (PIC) simulations of collisionless jets of electrons and positrons in an ambient electron-proton plasma have revealed an acceleration of positrons at the expense of electron kinetic energy. The dominant instability within the jet was a filamentation instability between electrons, protons and positrons. In this work we show that a filamentation instability, between an initially unmagnetized ambient electron-proton plasma at rest and a beam of pair plasma that moves through it at a non-relativistic speed, indeed results in preferential positron acceleration. Filaments form that are filled predominantly with particles with the same direction of their electric current vector. Positron filaments are separated by electromagnetic fields from beam electron filaments. Some particles can cross the field boundary and enter the filament of the other species. Positron filaments can neutralize their net charge by collecting the electrons of the ambient plasma while protons cannot easily follow the beam electron filaments. Positron filaments can thus be compressed to a higher density and temperature than the beam electron filaments. Filament mergers, which take place after the exponential growth phase of the instability has ended, lead to an expansion of the beam electron filaments, which amplifies the magnetic field they generate and induces an electric field in this filament. Beam electrons lose a substantial fraction of their kinetic energy to the electric field. Some positrons in the beam electron filament are accelerated by the induced electric field to almost twice their initial speed. The simulations show that a weaker electric field is induced in the positron filament and particles in this filament hardly change their speed.

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通过电子-质子束和一对等离子体束之间的丝状不稳定性优先加速正电子

环境电子-质子等离子体中电子和正电子的无碰撞射流的胞内粒子 (PIC) 模拟揭示了以电子动能为代价的正电子加速。射流内的主要不稳定性是电子、质子和正电子之间的丝状不稳定性。在这项工作中，我们表明，在最初未磁化的静止环境电子 - 质子等离子体和以非相对论速度穿过它的一对等离子体束之间的丝状不稳定性确实导致优先正电子加速。形成的细丝主要填充与电流矢量方向相同的粒子。正电子丝通过电磁场与束电子丝分离。一些粒子可以穿过场边界并进入其他物种的细丝。正电子丝可以通过收集周围等离子体的电子来中和它们的净电荷，而质子不能轻易跟随束电子丝。因此，正电子丝可以被压缩到比束电子丝更高的密度和温度。在不稳定的指数增长阶段结束后发生的灯丝合并导致束电子灯丝的膨胀，这会放大它们产生的磁场并在该灯丝中感应出电场。束电子在电场中损失了大部分动能。束电子灯丝中的一些正电子被感应电场加速到几乎两倍于它们的初始速度。