A micron-sized negatively charged particle in a complex plasma is typically surrounded by an ion stream. The latter is focused by the former and shapes the region of elevated ion concentration (ion wake). As a result, the interaction between dust particles in a complex plasma involves both a force governed by the screened interaction of the charges of the particles and additional parametric interactions. One is associated with attraction to the ion wake of a nearby particle and the other with a change of charge of a particle in the ion wake of another particle. This parametric interaction can be seen as an imaginary violation of Newton's third law and can lead to various types of instabilities in the ensemble of dust particles. In this work, individual particles with a diameter of $7.17\mu \text{m}$ move above a monolayer of $10.41\mu \text{m}$ particles in plasma sheath. The light particle temporarily becomes localized above one of the larger particles in the course of its movement. The resulting pairs perform finite, persistent motion. Three-dimensional analysis of this motion allows us to estimate the charges of the dust particles, measure the relative change in charge of the lower particle located in the ion wake under the upper particle, and quantitatively assess the attraction force exerted by the ion wake on the lower particle.

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• High-frequency & RF discharges in plasmas
• Dusty or complex plasma
• Low-temperature plasma
• Plasma sheaths & surfaces
• Strongly-coupled plasmas
• Electric & magnetic plasma measurements
• Imaging & optical processing