Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 82234 Wessling, Germany.
Molecules. 2021 Jan 9;26(2):308. doi: 10.3390/molecules26020308.
Possible mechanisms of particle attraction providing formation of the field aligned microparticle strings in complex plasmas at elevated gas pressures are theoretically investigated in the light of the Plasmakristall-4 (PK-4) experiment on board the International Space Station. The particle interaction energy is addressed by two different approaches: (i) using the dynamically screened wake potential for small Mach numbers derived by Kompaneets et al., in 2016, and (ii) introducing effect of polarization of the trapped ion cloud by discharge electric fields. Is is found that both approaches yield the particle interaction energy which is independent of the operational discharge mode. In the parameter space of the performed experiments, the first approach can provide onset of the particle attraction and string formation only at gas pressures higher than 40-45 Pa, whilst the mechanism based on the trapped ion effect yields attraction in the experimentally important pressure range 20-40 Pa and may reconcile theory and observations.
可能的粒子吸引机制为在复杂等离子体中提供了沿磁场方向排列的微粒子串的形成，这在理论上根据国际空间站上的 Plasmakristall-4（PK-4）实验进行了研究。使用 Kompaneets 等人在 2016 年推导的针对小马赫数的动态屏蔽尾流势，以及（ii）引入放电电场对被俘获离子云的极化效应，来处理粒子相互作用能。发现这两种方法都给出了与操作放电模式无关的粒子相互作用能。在所进行的实验的参数空间中，第一种方法只能在气体压力高于 40-45 Pa 时提供粒子吸引和串形成的起始，而基于被俘获离子效应的机制则在实验上重要的压力范围内（20-40 Pa）产生吸引力，并可能协调理论和观测结果。
