Activity of comets: Gas Transport in the Near-Surface Porous Layers of a Cometary NucleusReportar como inadecuado

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* Corresponding author 1 MPS - Max Planck Institute for Solar System Research 2 Technische Universität Braunschweig Braunschweig 3 UvA - University of Amsterdam Amsterdam

Abstract : ►Knudsen-s formula widely used in cometary research is of limited accuracy for modeling the gas transport through short dust channel. As an alternative, Clausing-s formula is suggested, accurately describing the kinetics of transport through a single cylindrical capillary. ► Accurate statistical calculations are performed for media formed either by ballistic deposition RDB of test particles or by random filling of a control volume RSP. The medium permeability and the return flow of re-condensed molecules are estimated for the different model parameters. The permeability depends on the medium porosity in a nonlinear way. ► We preserve the overall structure of Clausing-s formula and introduce the effective radius of the capillary is an unknown function of porosity. The explicit form of this functional dependence is derived from a nonlinear approximation based on statistical modeling results. ► The retrieved algebraic expression allows us to accurately calculate the permeability of layers whose thickness and porosity vary in the range of values expected for the near-surface regions of a cometary nucleus. The simplicity of this approach makes it practical to include the block that describes the transport of gas in the overall thermal model of a cometary nucleus.

Mots-clés : Comets Nucleus Gas Dust

Autor: Yuri V. Skorov - Rik Van Lieshout - Jürgen Blum - Horst U. Keller -



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