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V. Tenishev, M. Combi (AOSS/U. Michigan), B. Davidsson (ESTEC, Noordwyck)
The cometary atmosphere is a unique phenomenon in the solar system. It represents a highly extended dusty gas cloud covering a huge range of physical conditions varying from fluid to collisionless at different locations within the coma and at different times. Kinetic methods, as opposed to fluid, are the most universally suitable tools for simulating processes in cometary comae.
Comet 67P/Churyumov-Gerasimenko is the target of the Rosetta mission, making development of dusty-gas coma models of great practical importance. A multi-species dusty-gas model has been developed that is based on the Direct Simulation Monte Carlo (DSMC) approach. The model was utilized to study the coma of comet 67P/Churyumov-Gerasimenko over a range of conditions from the very tenuous conditions after Rosetta encounter time when all instruments are turned on (r = 3.25 AU and Q = 1024 s-1) to more active conditions near perihelion (r=1.29 AU and Q = 5 x 1027 s-1). An analysis of 2D-axisymmetric dust and gas distributions within the coma emanating from a realistic nucleus-surface boundary description extending out to 1 million km is described. The nucleus is modeled as a sphere, homogeneously covered by a porous ice-dust mixture, which sublimates according to local illumination conditions. A thermophysical nucleus model including processes such as layer energy absorption, volume sublimation/recondensation and internal transport of heat and mass is used to calculate local production rates, scaled to yield the total values mentioned above.
Partial support for this work was provided by NASA grant NAG5-13239 from the Planetary Atmospheres program, grants NAG5-13404 and NAG5-9464 from the Applied Information Systems Research program, as well as by the International Space Science Institute.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.