SODIUM VELOCITIES AND SOURCES IN HALE-BOPP

We use spatially resolved high-resolution spectra of the 5890 and 5896 Angstrom sodium D lines in the nuclear regions of Comet Hale-Bopp to determine the sources of cometary sodium. Comparison of the data to a Monte Carlo model of sodium dynamics suggests that the intensities and velocities of sodium in HaleBopp can be explained if 55% of the obser ved sodium is produced at the nucleus, the remaining 45% is produced i n an extended source, and the sodium is accelerated by solar radiation pressure. Observations of H2O+ in Hale-Bopp and subsequent modeling o f a plasma-derived sodium source show that this source produces sodium at higher velocities than those observed; any contribution from such a source must be small. The combined nucleus and extended sources of s odium which fit our data best would create a sodium tail at a scale 10 0 times larger than that of these observations identical in morphology and velocity to that observed in Hale-Bopp. (C) 1998 Academic Press.