Birte Salome Klug

• Up to hundreds of tons of cosmic material enter the Earth’s atmosphere every day, where incoming interplanetary solids of suitable size and speed ablate at altitudes above 80 km. Subsequent recombination and polymerization of the vaporized material and further agglomeration is thought to form nanometer-sized aerosols, which are denoted as meteoric smoke particles (MSP). At the appropriate altitude between 82 and 85 km, mesospheric ice clouds, so-called noctilucent clouds (NLC), occur. Till now, the nature of condensation nuclei for the formation of NLC elements has not been conclusively explained. However, existing studies suppose that MSP can serve as possible ice condensation nuclei, but experimental evidence is lacking heretofore. To gain further insights into high atmosphere processes, in-situ measurements to collect cloud elements (as impactions on substrates, with subsequent physico-chemical analyses) are required. However, measurements at such altitudes are complex and cost-intensive and are only possible by means of sounding rockets, which is why only a sparse measurement database is available. The aim of this study is the mathematical and numerical modeling of the impaction processes coupled to the fluid dynamics to support the development of an inertia-based probe collector mounted on a sounding rocket. Compressible Navier-Stokes equations are numerically solved to analyze the supersonic flow field with Mach numbers of 1.31 and 1.75 at 85 km altitude around the instrument module of the sounding rocket under various flight attitudes. Flow patterns are investigated for the arrangement, orientation, and aerodynamic design of the collectors. Simulations of particle trajectories based on Newton’s second law under the consideration of the Stoke’s drag and Brownian force in the near-field of the collectors under consideration of different flight attitudes and particle number concentrations in a supersonic flow confirm the effectivity of the particle collection by the developed design of the collectors. Simulation results show that impactions on the designated collector surfaces are highly probable. Subsequent physico-chemical analyses of the collected particulate material may provide observational evidence for the presumed presence of MSP as well as information on the morphology and chemical composition. Consequently, their presence in the sample can confirm the hypothesis of the role of MSP as condensation nuclei for mesospheric ice particles.