An advanced physical model of cometary activity

Родионов, А. В.; Crifo, J. F.; Szegö, K.; Lagerros, J. S. V.; Fulle, M.

doi:10.1016/s0032-0633(02)00047-8

Cited by 54 publications

(35 citation statements)

References 50 publications

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“…We solve numerically the equations of motion of P/Halley's nucleus, taken to be an asymmetric rigid top, and taking into account the torque due to the gas rocket forces (Rodionov et al 2001), and the solar tidal torque (Schutz 1981). To compute the value of the torque due to outgassing, we solve the dirty ice sublimation equations at each point of the sunlit surface, with the assumption that the icy area fraction, that is the ratio between the dust and ice on the surface, is everywhere f = 0.6 (Crifo 1997).…”

Section: Nucleus Rotation Modelmentioning

confidence: 99%

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Dynamical effects of comet P/Halley gas production

Szegö

Crifo

Foldy

et al. 2001

A&A

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Abstract.We revisit the rotation of P/Halley taking into account the most essential observational constraints, as well as the external torques affecting the nucleus, in particular the outgassing torque. We solve the dirty ice sublimation equations at each point of the sunlit surface, using, for the first time, the surface shape derived from the 1986 flybys imaging data. We assume that the nuclear surface is homogeneous in composition, thus reducing the number of model free parameters to one only: the dust-to-ice ratio on the surface. Our derived rotation model is a short-axis mode; it is consistent both with the 1986 nucleus imaging data, with the estimated non gravitational force, and with the observed time variations of the nucleus production rates. The outgassing torque results in a significant variation of the angular momentum vector -for the assumed nucleus density of 0.5 g/cm 3 .

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Section: Nucleus Rotation Modelmentioning

confidence: 99%

“…Finally, the effect of the torque due to the outgassing of the nucleus and to the solar tide were seldom considered. In this brief report we revisit the rotation of the nucleus of comet P/Halley based on the approach of Crifo (1997) and Rodionov et al (2001), which takes into account these effects self-consistently.…”

Section: Introductionmentioning

confidence: 99%

Dynamical effects of comet P/Halley gas production

Szegö

Crifo

Foldy

et al. 2001

A&A

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“…The vacuum outflow of the molecules emitted by the nucleus is computed using the gasdynamical approach described in Rodionov et al (2002), except that the method of solutions here is more powerful than the one described there, as one true timedependent solutions is acquired (in lieu of a succession of steady state solutions). Thus, the time dependent tridimensional Euler Equations governing the gas outflow are solved by the shockcapturing Godunov method, using periodic boundary conditions for the integration over time.…”

Section: Molecular Outflow Modelmentioning

confidence: 99%

“…A gas is said to be in fluid regime, transition regime, or freemolecular regime, according to whether its velocity distribution is a Maxwellian, a first-order-distorted Maxwellian, or a nonMaxwellian function (see e.g., Rodionov et al 2002). If the hypersonic approximation holds, this distinction is immaterial to compute the pressure force from coma gas parameters.…”

Section: Validity Of the Present 3d+t Eulerian Solutionmentioning

confidence: 99%

An analysis of outgassing pressure forces on the Rosetta orbiter using realistic 3D+t coma simulations

Mysen¹,

Родионов

Crifo

2010

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A model for the interaction between a multicomponent Maxwellian atmosphere and a spacecraft is described. Multidimensional, time-dependent gasdynamical simulations of the gas coma around the recently reconstructed aspherical rotating nucleus of comet 67P/C-G is used to analyze the outgassing pressure forces on the ESA spacecraft Rosetta. The forces were in general found to be directed significantly away from the cometocentric position vector of the spacecraft. It was also found that in a maximum outgassing scenario at comet rendezvous, the outgassing pressure force exceeds the gravitational attraction from the nucleus in the cometocentric direction of the Sun. Furthermore, the highly non-spherical pressure field was found to undergo very large changes as the nucleus rotated. Still, it was possible to represent the mean pressure field experienced by Rosetta by a fairly simple model, which can be used for the determination of the comet mass and the so-called oblateness coefficient c 20 from the spacecraft Doppler signal. The oblateness coefficient represents a type of asphericity of the gravity field. The determination of the so-called triaxiality coefficient of the gravity field c 22 may require using the true pressure field instead of the mean pressure field.

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“…It is easy to show that these assumptions imply nonconservation of the flow momentum. This raises the question of which physical process(es) could produce such an effect hitherto never advocated in the outer coma (see e.g., Rodionov et al 2002).…”

Section: Introductionmentioning

confidence: 99%

First attempt at interpreting millimetric observations of CO in comet C/1995 O1 (Hale-Bopp) using 3D+t hydrodynamical coma simulations

Boissier¹,

Bockelée‐Morvan

Родионов

et al. 2010

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Context. Millimetre line observations of comet C/1995 O1 (Hale-Bopp) close to perihelion, completed using the IRAM Plateau de Bure Interferometer, have detected temporal variations in the CO J(2-1) 230 GHz line shape, and in the position of its maximum emission brightness within the field-of-view, whose heuristic analysis has suggested the presence in the coma of a slowly rotating spiral-shaped enhancement of the CO density. Aims. Here, we reanalyse these data using a physically consistent model of the coma. Methods. We consider a large, rotating, icy nucleus with an arbitrarily aspherical shape and an adhoc rotation mode, and compute its tridimensional, time-dependent ("3D+t") mixed CO + H 2 O coma, using a previously developed tridimensional hydrodynamical code (HDC). The line emission of CO is then computed using a molecular excitation and radiation transfer code (ERC). In the present, pioneering phase, the HDC and ERC both contain crude, and not thoroughly mutually consistent approximations. Several alternative CO surface flux distributions are considered, and the resulting CO 230 GHz line spectra and brightness maps are compared with observations. Results. We find that when an uniform surface flux of CO is assumed, the spiral structures created by the nucleus asphericity in the CO coma are too faint to account for the observational data, whereas we confirm earlier conclusions based on a heuristic approach that the assumption of an area of suitable dimensions and localization with increased CO flux leads to results in agreement with a large subset of (but not all) the data. This suggests that the true CO coma production map may be more complex than the presently assumed rather simple-minded one. Refined and mutually consistent HDC and ERC are needed for a more satisfactory interpretation of the present and any similar future data.

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An advanced physical model of cometary activity

Cited by 54 publications

References 50 publications

Dynamical effects of comet P/Halley gas production

Dynamical effects of comet P/Halley gas production

An analysis of outgassing pressure forces on the Rosetta orbiter using realistic 3D+t coma simulations

First attempt at interpreting millimetric observations of CO in comet C/1995 O1 (Hale-Bopp) using 3D+t hydrodynamical coma simulations

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