Challenging a Paradigm: Do We Need Active and Inactive Areas to Account for Near-Nuclear Jet Activity? |
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Authors: | Crifo J-F Rodionov A V Szegö K Fulle M |
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Institution: | (1) Service d'Aéronomie du CNRS, BP 3, F, 91371 Verriéres le Buisson Cedex, France;(2) Central Research Institute on Machine Building (TsNIIMASCH), Pionyerskaya St., 4, Korolev, Moscow Region, 141070, Russia;(3) KFKI Research Institute for Particles and Nuclear Physics, PO Box 49, H-1525 Budapest, Hungary;(4) Osservatorio Astronomico di Trieste, Via Tiepolo, 11, I-34131 Trieste, Italy |
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Abstract: | We briefly describe an advanced 3D gas dynamical model developed for the simulation of theenvironment of active cometary nuclei.
The model canhandle realistic nucleus shapes and alternative physical models for the gas and dust production mechanism.The
inner gas coma structure is computed by solving self-consistently(a) near to the surface the Boltzman Equation(b) outside
of it, Euler or Navier-Stokes equations.The dust distribution is computed from multifluid ``zero-temperature' Euler equations,extrapolated
with the help of a Keplerian fountain model.The evolution of the coma during the nucleus orbital and spin motion,is computed
as a succession of quasi-steady solutions. Earlier versions of the model using simple,``paedagogic' nuclei have demonstrated
that the surface orographyand the surface inhomogeneity contribute similarly to structuring the near-nucleusgas and dust coma,casting
a shadow on the automatic attribution of such structures to ``active areas'.The model was recently applied to comet P/Halley,
for whichthe nucleus shape is available. In the companion paper of this volume,we show that most near-nucleus dust structuresobserved
during the 1986 Halley flybys are reproduced, assuming that the nucleus is strictly homogeneous. Here, we investigate the
effect of shape perturbations and homogeneityperturbations. We show that the near nucleus gas coma structure is robust vis-a-vissuch
effects. In particular, a random distribution of active and inactive areaswould not affect considerably this structure, suggesting that such areas,even if present, could not be easily identified on images
of the coma. |
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Keywords: | Comets dust gas P/Halley structure |
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