Complex/Dusty Plasmas in Space*

Dust particles, once they are reaching sizes of micrometers, they are strongly affected by gravity. In complex/dusty plasmas experiments they sediment towards the lower electrode where the charged dust particles can be levitated by a strong electric field. This allows the investigation of 2-dimensional dusty plasmas in a very inhomogeneous region. To investigate the interaction of dust in the homogeneous environment of the bulk plasma, microgravity experiments are performed and complement the research on the ground. More than two decades continuous dusty plasma research has been performed in the PK-program on the ISS (PK stands for PlasmaKristall = plasma crystal). Fundamental topics have been investigated like charging, ion drag, or wave propagation. But also new topics arose, which were only possible to investigate under microgravity conditions, like phase separation or lane formation in binary dust particle mixtures, or electrorheological plasmas. While on the one side these results are important in understanding dusty plasmas in general, the systems formed under microgravity are also important as a model system of classical condensed matter allowing the observation of dynamical, strong coupling phenomena on the most fundamental – the kinetic level.

In this presentation recent results from the PK-4 laboratory on the ISS will be combined with the knowledge gained from the facilities PKE-Nefedov (2001-2005 on the ISS) and PK-3 Plus (2006-2013 on the ISS) to overview complex/dusty plasma research under microgravity conditions. In the outlook future perspectives of low gravity research will be discussed and the next facility for the ISS – the Complex Plasma Facility COMPACT, a multi-user and multi-purpose facility – will be presented.