Counterstreaming electron beams drifting along the magnetic field in electron–proton plasmas may lead to the generation of electrostatic (ES) waves and structures widely observed in planetary magnetospheres. In electron–positron plasmas, streaming electron/positron beams along the background magnetic field may first result in ES waves followed by the electromagnetic (EM) waves with substantial magnetic field perturbations, as shown by Jao and Hau [Phys. Rev. E 98, 013203 (2018)]. In this study, we examine the formation of ES and EM waves driven by current free counterstreaming electron beams in electron–ion background plasmas and current free electron–positron beams in electron–proton–positron background plasmas based on one-dimensional EM particle-in-cell simulations with the drift velocity being along the background magnetic field. For the former cases, the effects of ion-to-electron mass ratios are examined, which have implications for two- and three-dimensional particle in cell simulations with reduced mass ratios. For the latter cases, the effects of positrons are examined, which have applications to astrophysical plasma environments and laboratory experiments. It is shown that the presence of positrons or light ions may shorten the occurrence times between the ES and EM waves driven by current free electron beam instability. The EM waves have relatively longer wavelengths as compared to the ES waves and the magnetic field evolution resembles parallel proton firehose instability. The effects of positrons, background compositions, and ion-to-electron mass ratios on the occurrence of ES and EM waves are consistent with the linear fluid theory.

中文翻译：

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电流自由电子束不稳定性驱动的静电波和电磁波：正电子，背景成分和离子电子质量比的影响

沿电子-质子等离子体中的磁场漂移的逆流电子束可能导致产生静电（ES）波和在行星磁层中广泛观察到的结构。在电子-正电子等离子体中，沿着背景磁场流过的电子/正电子束可能首先产生ES波，然后产生具有实质性磁场扰动的电磁（EM）波，如Jao和Hau [Phys。E 98版，013203（2018）]。在这项研究中，我们基于一维EM粒子输入，研究了由电子离子背景等离子体中的自由电流逆流电子束和在电子质子-正电子背景等离子体中的自由电流电子-正电子束驱动的ES和EM波的形成-细胞模拟，漂移速度沿着背景磁场。对于前一种情况，研究了离子与电子质量比的影响，这对于降低质量比的电池模拟中的二维和三维粒子具有影响。对于后一种情况，检查了正电子的作用，这些作用已应用于天体等离子体环境和实验室实验。结果表明，正电子或轻离子的存在可以缩短由电流自由电子束不稳定性驱动的ES波和EM波之间的发生时间。与ES波相比，EM波具有相对较长的波长，并且磁场演化类似于平行质子的流管不稳定性。正电子，本底组成和离子电子质量比对ES和EM波发生的影响与线性流体理论一致。