The Streaming Instability, Photophoresis and Planetesimal Formation at the Inner Edge of Protoplanetary Disks

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State of the art scenarios of planet and planetesimal formation are based on the evolution of small particles in dense disks of gas and dust. The particles evolve in size and are supposed to be concentrated in pressure bumps or instabilities only to collapse by gravity, eventually. However, even though these processes are considered as being most fundamental, the concentration and instabilities have never been verified experimentally. Therefore, for the first time, the formation of over dense clouds of particles in a gaseous environment under the influence of stellar radiation and the formation of streaming instabilities will be simulated in a combination of laboratory experiments and numerical simulations. This scenario is focused on the pre-planetary evolution at the inner edge of protoplanetary disks. In the laboratory experiments particle clouds in a thin gas environment will be generated. The size evolution as well as the density distribution of the cloud in forming streaming instabilities will be determined. The same experiment will be carried out numerically. Based on the results the evolution of dust at the inner edge of protoplanetary disks up to planetesimals will be simulated. This way, combining both, experiment and theory, current ideas of planet formation are verified in general and models for the formation of planetesimals at the edges of protoplanetary disks are developed more specifically, for which no predictions exist so far.