Microparticle suspensions in a polarity-switched discharge plasma of the Plasmakristall-4 facility on board the International Space Station exhibit string-like order. As pointed out in [Phys. Rev. Research 2, 033314 (2020)], the string-order is subject to evolution on the timescale of minutes at constant gas pressure and constant parameters of polarity switching. We perform a detailed analysis of this evolution using the pair correlations and length spectrum of the string-like clusters (SLCs). Average exponential decay rate of the SLC length spectrum is used as a measure of string order. The analysis shows that the improvement of the string-like order is accompanied by the decrease of the thickness of the microparticle suspension, microparticle number density, and total amount of microparticles in the field of view. This suggests that the observed long-term evolution of the string-like order is caused by the redistribution of the microparticles, which significantly modifies the plasma conditions.

中文翻译：

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PK-4实验中弦流体复合等离子体三维结构的长期演化

国际空间站上 Plasmakristall-4 设施的极性转换放电等离子体中的微粒悬浮液呈现出串状排列。正如[ Phys. 修订版研究 2, 033314 (2020)]，在恒定气压和恒定极性切换参数下，弦序在分钟的时间尺度上会发生演变。我们使用串状簇 (SLC) 的对相关性和长度谱对这种演变进行了详细分析。SLC 长度谱的平均指数衰减率用作字符串顺序的度量。分析表明，串状有序度的提高伴随着微粒悬浮液的厚度、微粒数密度和视野中微粒总量的降低。这表明观察到的弦状有序的长期演变是由微粒的重新分布引起的，这显着改变了等离子体条件。