TY  - GEN
A1  - Seiß, Martin
A1  - Spahn, Frank
T1  - Hydrodynamics of Saturn’s dense rings
T2  - Postprints der Universität Potsdam : Postprint Mathematisch Naturwissenschaftliche Reihe
N2  - The space missions Voyager and Cassini together with earthbound observations re-vealed a wealth of structures in Saturn’s rings. There are, for example, waves being excited at ring positions which are in orbital resonance with Saturn’s moons. Other structures can be assigned to embedded moons like empty gaps, moon induced wakes or S-shaped propeller features. Further-more, irregular radial structures are observed in the range from 10 meters until kilometers. Here some of these structures will be discussed in the frame of hydrodynamical modeling of Saturn’s dense rings. For this purpose we will characterize the physical properties of the ring particle ensemble by mean field quantities and point to the special behavior of the transport coefficients. We show that unperturbed rings can become unstable and how diffusion acts in the rings. Additionally, the alternative streamline formalism is introduced to describe perturbed regions of dense rings with applications to the wake damping and the dispersion relation of the density waves.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 574 
KW  - granular gas
KW  - instabilities
KW  - hydrodynamics
KW  - planetary rings
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413139
SP  - 191
EP  - 218
ER  - 
TY  - GEN
A1  - Sandin, Christer
A1  - Steffen, Matthias
A1  - Jacob, Ralf
A1  - Schönberner, Detlef
A1  - Rühling, Ute
A1  - Hamann, Wolf-Rainer
A1  - Todt, Helge Tobias
T1  - The role of heat conduction to the formation of [WC]-type planetary nebulae
T2  - Proceedings of the International Astronomical Union
N2  - X-ray observations of young Planetary Nebulæ (PNe) have revealed diffuse emission in extended regions around both H-rich and  H-deficient central stars. In order to also repro-duce physical properties of H-deficient objects, we have, at first, extended our time-dependent radiation-hydrodynamic models with heat conduction for such conditions. Here we present some of the important physical concepts, which determine how and when a hot wind-blown bubble forms. In this study we have had to consider the, largely unknown, evolution of the CSPN, the slow (AGB) wind, the fast hot-CSPN wind, and the chemical composition. The main conclusion of our work is that heat conduction is needed to explain X-ray properties of wind-blown bubbles also in H-deficient objects.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 582 
KW  - conduction
KW  - hydrodynamics
KW  - planetary nebulae: general
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-413702
SN  - 1866-8372
IS  - 582
SP  - 494
EP  - 495
ER  -