Analysis of anisotropic dust-dust interaction potential in a microgravity dusty plasma

Studying the dynamics of charged microparticles (dust) suspended in plasma is a rich topic of research that provides a unique window into the study of self-organization and stability of complex systems. Due to the macroscopic size of the dust, a conventional camera can be used to directly image the dust at the kinetic level. Thus, all of phase space can be sampled and used to investigate the properties of different structural states and transitions. Here we present analysis of microgravity dusty plasma from the Plasmakristall-4 (PK-4) facility on board the International Space Station where arrangements of filamentary dust structures have been observed to emerge under external electric field in a large plasma parameter space. The investigation of the form of the anisotropic dust-dust interactions is of particular interest; it can reveal whether the observed filamentary structures are reminiscent of an electrorheological or a liquid crystal state. We present analysis of the particle dynamics from several PK-4 experiments using particle tracking velocimetry techniques along with novel machine learning methods which exploit sparse regression techniques. The interaction anisotropies inferred from experiments using these methods are compared against the predictions from molecular dynamics simulations.