Analysis of Raman scattered LY‐α emissions from the atmosphere of Uranus

A line at 1280 Å, due to Raman scattering of solar Lyman alpha (Ly‐α) in the atmosphere of Uranus, has been detected by the Voyager Ultraviolet Spectrometer. The measured intensity of 40 ± 20 R implies that 200 R to 500 R of the measured 1500 R Ly‐α intensity at the sub‐solar point is due to Rayleigh scattering of the solar line. The presence of Rayleigh and Raman scattering at 1216 Å suggests that the Uranian atmosphere is largely devoid of absorbing hydrocarbons above the 0.5 mbar level. The most natural explanation of this depletion is very weak vertical mixing equivalent to an eddy coefficient on the order of 200 cm² s⁻¹ between 0.5 mbar and 100 mbar.