Effect of ionization waves on dust chain formation in a DC discharge

TL;DR

This paper investigates how ionization waves influence dust chain formation in a DC discharge, combining experiments and multi-scale simulations to understand the inhomogeneous electric fields and resulting dust structures.

Contribution

It introduces a multi-scale numerical model to analyze the impact of ionization waves on dust grain charging and string formation in complex plasma under DC discharge conditions.

Findings

Ionization waves cause significant electric field oscillations.

Dust grains form string-like structures influenced by ion wakefields.

Model results align with PK-4 experimental observations.

Abstract

An interesting aspect of complex plasma is its ability to self-organize into a variety of structural configurations and undergo transitions between these states. A striking phenomenon is the isotropic-to-string transition observed in electrorheological complex plasma under the influence of a symmetric ion wakefield. Such transitions have been investigated using the Plasma Kristall-4 (PK-4) microgravity laboratory on the International Space Station (ISS). Recent experiments and numerical simulations have shown that, under PK-4 relevant discharge conditions, the seemingly homogeneous DC discharge column is highly inhomogeneous, with large axial electric field oscillations associated with ionization waves occurring on microsecond time scales. A multi-scale numerical model of the dust-plasma interactions is employed to investigate the role of the electric field on the charge of individual dust grains, the ion wakefield, and the order of string-like structures. Results are compared to dust strings formed in similar conditions in the PK-4 experiment.