Nonlinear dust acoustic waves in a plasma under microgravity conditions.

Nonlinear dust acoustic waves were investigated in a plasma under microgravity conditions, using the European Space Agency facility PK-4 on the International Space Station (ISS). A large three-dimensional cloud of dust particles was confined near a radio-frequency coil that powered a glow discharge in low-pressure neon gas. Low-frequency dust acoustic waves were spontaneously excited, due to the flowing ions in the plasma. The waves were nonlinear, with a large amplitude. Experimental spectra for dust particle motion were obtained, using the particle position data from an analysis of the images of the particle motion. Nonlinear phenomena are discussed, including nonsinusoidal waveform shape and indicator of wave synchronization. All authors acknowledge the joint ESA/Roscosmos ``Experiment Plasmakristall-4'' onboard the International Space Station. Work was partially supported by DLR Grant Nos. 50WM1441 and 50WM1742. Work at Iowa was supported by NASA-JPL subcontracts 1573629 and 1579454, and the NSF Award No. 1740379.