AN EXTENDED SOURCE FOR CN JETS IN COMET P-HALLEY

We examined radial intensity profiles of CN jets in comparison with th e diffuse, isotropic component of the CN coma of Comet P/Halley. All i mages were bias-subtracted, flat-fielded, and continuum-subtracted. We calculated the diffuse profiles by finding the azimuthal mean of the coma least contaminated by jets yielding profiles similar to those of vectorial and Haser models of simple photodissociation. We found the j et profiles by calculating a mean around a Gaussian-fitted center in r -theta space. There is an unmistakable difference between the profiles of the CN jets and the profiles of the diffuse CN. Spatial derivative s of these profiles, corrected for geometrical expansion, show that th e diffuse component is consistent with a simple photodissociation proc ess, but the jet component is not. The peak production of the jet prof ile occurs 6000 km from the nucleus at a heliocentric distance of 1.4 AU. Modeling of both components of the coma indicate results that are consistent with the diffuse CN photochemically produced, but the CN je ts need an additional extended source. We found that about one-half of the CN in the coma of Comet P/Halley originated from the jets, the re st from the diffuse component. These features, along with the width of the et being approximately constant, are consistent with a CHON grain origin for the jets. (C) 1994 Academic Press, Inc.