Electrostatic modes in collisional complex plasmas under microgravity conditions.

A linear dispersion relation in a highly collisional complex plasma, including ion drift, was derived in the light of recent PKE-Nefedov wave experiment performed under microgravity conditions onboard the International Space Station. Two modifications of dust density waves with wave frequencies larger than the dust-neutral collision frequency were obtained. The relevance to the space observations was analyzed and a comparison of theory and observations was made for two different complex plasma domains formed by small and large microparticles. Good qualitative agreement is found between the measurements and the theoretical dispersion relations. This allows a determination of the basic complex plasma parameters.