  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.

Plasma Physics