Observational studies of comets frequently investigate the dust coma, including its basic shape and morphology. A simple means of quantifying one coma property is to measure the radial surface brightness profile and extract its slope, and because it is easy to measure, this value has been presented in many papers. Unfortunately, the effects of different coma mechanisms on the radial profile are not well understood, so interpretations of the result are usually stated in generalities as compared to the canonical coma model of a nucleus producing a steady-state dust outflow that exhibits a constant slope of -1. Differences from this value are said to indicate variations from the standard model, which can be caused by temporal changes in dust production, radiation pressure, or alteration of the physical characteristics of the grains (fragmentation, sublimation, changes in optical properties, etc.).We are using a Monte-Carlo model of cometary comae to explore how different mechanisms affect the morphology of the coma and the shape and slope of the radial surface brightness profiles. We can generate artificial comet comae under a large variety of circumstances to characterize their appearance and measure the radial profiles in each case. Averaged radial profiles, as well as profiles in specific directions, are used to explore the signatures of the various mechanisms and results are compiled for a representative sample of viewing geometries. The ultimate goal of this study is to identify the characteristics that are unique to each mechanism acting on the coma and to quantify the radial profile measurements so that the results can be used by other investigators as a diagnostic tool for interpreting their own observational data. We will present the early results of this study and discuss the characteristics that are found. This work is funded by the NASA Planetary Atmospheres program grant NNG05GP58G.
AAS/Division for Planetary Sciences Meeting Abstracts #39
- Pub Date:
- October 2007