Exploitable results Numerical simulation of cometary surface phenomena Physical processes taking place inside and immediately above the surface of a cometary nucleus have been investigated. In particular, the influence of surface roughness (gaps, caverns, and pore structure on various size scales) on the gas emission of a comet were modeled in some detail. Basic assumptions for the modeling were two currently debated scenarios regarding the structure of a comet nucleus: the dirty iceball (F. Whipple) and the icy dirtball (H.U. Keller) model. In the latter case the formation of long cohesive channels with nonvolatile walls (where the sublimated gases flow through) is possible, while in the former case the emission of gases comes from caverns with icy bottom and walls. The evolution of the shape of the gas-emitting icy surface in response to heating by the sun was modeled by two different methods: (i) Analytical integration of the relevant equations (hereby being restricted to simple geometries, as e.g. rectangular boxes) and (ii) Monte Carlo simulations. The latter method is much more general and allows investigation of arbitrary configurations. A further problem area addressed was the structure and evolution of the Knudsen layer immediately above the active cometary nucleus. Direct Monte Carlo simulations show how the distribution function after a sudden change (e.g. blow-off of a dust mantle) relaxes towards a new equilibrium. Wyszukiwanie danych OpenAIRE... Podczas wyszukiwania danych OpenAIRE wystąpił błąd Brak wyników
