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SFB 963:  Astrophysikalische Strömungsinstabilität und Turbulenz

Fachliche Zuordnung Physik
Förderung Förderung von 2012 bis 2016
Projektkennung Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 187005812
 
Erstellungsjahr 2017

Zusammenfassung der Projektergebnisse

Flow Instabilities and Turbulence is a ubiquitous phenomenon in astrophysics. The overall purpose of the CRC Astrophysical Flow Instabilities and Turbulence therefore was to understand the role of complex fluid flows in the physics of astrophysical objects. A deeper understanding of fundamental questions like Why do stars have magnetic fields? How do stars, planets, and galaxies form? require better understanding of the underlying physical processes from a combination of the rapidly improving observational data, numerical simulations, and laboratory experiments. On a large variety of scales, from the dense interiors of stars and planets to the highly rarefied intergalactic medium, fluid flows are universally present in astrophysics. Although these flows occur under very different conditions, they share the basic property that they are, in general, highly disordered in space and time. Most astrophysical flows occur under conditions where the driving forces generate large fluctuations in velocity and pressure with important consequences for the transport of energy and mass. Turbulence is one of the key processes for the structure and evolution of a large variety of geophysical and astrophysical systems. This universality of astrophysical turbulence interlinks the physics of the interior of planets and stars with proto-planetary or galactic disks, as well as the gas outside of galaxies. For example, angular momentum transport by turbulence is a central question that must be answered to understand how galaxies and stars form, how proto-planetary disks evolve, or how differential rotation is established in stars and planets. Magnetic field amplification through turbulent dynamo processes is ubiquitous in planets, stars, and galaxies. This CRC took advantage of the unique collection of research institutions and researchers in Göttingen to combine cutting-edge ground-based and space-based observations with theoretical and experimental work. The physical conditions that prevail in many astrophysical systems are extreme and thus observations are challenging to interpret. Theoretical insight and improved numerical simulations are essential to understand the observations. A specific strength of this CRC is the construction and use of unique experimental facilities to test theories in accessible parameter regimes. During the duration of this CRC we made progress on the topics of planetary and stellar dynamos, stellar rotation, solar convection, turbulence in the solar wind, laboratory experiments relevant to planet formation, fundamental fluid dynamics, and high-redshift structure formation. Some examples are the following: New helioseismic measurements imply that large-scale solar convective flows are much weaker than predicted by both theory and simulations (A01). Project A02 investigated in detail the coronal mass ejections (CME) and the CME-driven shocks can be detected in remote-sensing observations by coronagraphs and heliospheric imagers. The heliosphere as a gigantic plasma turbulence experiment was exploited, which explored the unique opportunity through in-situ measurements (CLUSTER) and modeling efforts (A03). Realistic simulations of magnetoconvection have been extended to simulate near-surface convection on stars on the lower main sequence. These simulations, when coupled with line formation calculations, will help with the interpretation of observations, including those from a new catalog of stellar activity observations (A04, A16). Among other topics, the dissipation in rocky planets for strong tidal forcing was investigated in A05. The transition to turbulence has been investigated in comparative laboratory and numerical experiments, based on a newly built Rayleigh–Bénard convection experiment (A06), while the structure formation in protoplanetary disks was investigated in two experimental setups (A07). In A11, a code for high-precision numerical simulation of nonradial nonlinear stellar pulsations has been developed. For the first time it could be demonstrated that subgrid-scale turbulence influences the formation of supermassive black holes by enhancing the accretion rate and suppressing fragmentation (A12). In close collaboration to A12 and A15, the hydrodynamical interaction of young galaxies with the intergalactic medium in state-of-the-art numerical simulations. A15 developed groundbreaking models to tackle the problem of numerically unresolved turbulence and magnetic reconnection in the context of large eddy simulations and further developed a sub-grid scale model to involve MHD turbulence in the simulation of reconnecting current sheets. A16 and A17 led to the discovery of very strong magnetic fields in fastest rotating M dwarfs. This discovery allows us for the first time to observe a clear differences in generated magnetic field geometry and strength between two distinct dynamo states operating in interiors of cool stars. On the modeling side the formation of starspots in self-consistent dynamo models could be obtained for the first time(A17). Substantial progress has been made on the detection and measurement of rotation periods in stars from the Kepler observations (A18).

Projektbezogene Publikationen (Auswahl)

 
 

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