Formation of Filaments and Nested Surfaces in Microgravity Dusty Plasma

This research examines the structure and spacing of particles within microgravity dusty plasma clouds using video data from the PlasmaKristall-4 (PK-4) apparatus onboard the International Space Station. The analysis focuses on experiments where gas pressure and current were varied to achieve different plasma conditions, which in turn affect the structural properties of the dust clouds. We analyze videos from a central region of the cloud as well as 3D-scans of the entire cloud. Positions of the particles in each video frame are obtained using particle tracking software, and then used to calculate pair correlation functions that show the probability of finding a particle a certain distance away from another particle. The obtained pair correlations reveal differences in the mean interparticle separation as a function of location in the cloud, gas pressure, and discharge current. We find that particles tend to organize in filamentary structures at the small scales, while forming nested spheroid shells at large scales. While particles within filaments are strongly coupled, suggesting crystalline order, the interaction of particles across filaments is liquid-like. These results provide evidence that the structures observed in the PK-4 have unique liquid crystalline properties.