Gas kinetics and dust dynamics in low-density comet comae

Details Gas kinetics and dust dynamics in low-density comet comae Gas kinetics and dust dynamics in low-density comet comae

Nov 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010icar..210..455d&link_type=abstract

Icarus, Volume 210, Issue 1, p. 455-471.

Physics

3

Scientific paper

Extensive regions of low-density cometary comae are characterized by important deviations from the Maxwell-Boltzmann velocity distribution, i.e. breakdown of thermodynamic equilibrium. The consequences of this on the shapes of emission and absorption lines, and for the acceleration of solid bodies due to gas drag, have rarely been investigated. These problems are studied here to aid in the development of future coma models, and in preparation for observations of Comet 67P/Churyumov-Gerasimenko from the ESA Rosetta spacecraft. Two topics in particular, related to Rosetta, are preparation for in situ observations of water, carbon monoxide, ammonia, and methanol emission lines by the mm/sub-mm spectrometer MIRO, as well as gas drag forces on dust grains and on the Rosetta spacecraft itself. Direct Simulation Monte Carlo (DSMC) modeling of H2O/CO mixtures in spherically symmetric geometries at various heliocentric distances are used to study the evolution of the (generally non-Maxwellian) velocity distribution function throughout the coma. Such distribution functions are then used to calculate Doppler broadening profiles and drag forces. It is found that deviation from thermodynamic equilibrium indeed is commonplace, and already at 2.5 AU from the Sun the entire comet coma displays manifestations of such breakdown, e.g., non-equal partitioning of energy between kinetic and rotational modes, causing substantial differences between translational and rotational temperatures. We exemplify how deviations from thermodynamic equilibrium affect the properties of Doppler broadened line profiles. Upper limits on the size of liftable dust grains as well as terminal grain velocities are presented. Furthermore, it is demonstrated that the drag-to-gravity force ratio is likely to decrease with decreasing cometocentric distance, which may be of relevance both for Rosetta and for the lander probe Philae.

Affiliated with

Also associated with

No associations

Rating

Gas kinetics and dust dynamics in low-density comet comae does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Gas kinetics and dust dynamics in low-density comet comae, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas kinetics and dust dynamics in low-density comet comae will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1487843