The Voyager 2 Ultraviolet Spectrometer measured the emission intensity of the He resonance line at 584 Å to be 0.34‐0.15+0.2 R on the day side of Neptune. Our calculations of the He 584 Å intensity at Neptune using partial frequency redistribution and inhomogeneous atmospheric models show that the product of the volume mixing ratio (mole fraction), fHe, and the eddy diffusion coefficient at the homopause, Kh, is fHeKh = 107 cm2 s−1 with upper and lower bounds to the uncertainty of about a factor of 3 and 9, respectively. If fHe is taken as the current Infrared Interferometer Spectrometer working value, fHe = 0.19, then Kh = 5×107 cm2 s−1 with a similar uncertainty. This range of K overlaps that obtained from analysis of the hydrocarbon distributions on Neptune (Broadfoot et al., 1989).
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)