Radio occultation of Jupiter's ring: Bounds on optical depth and particle size and a comparison with infrared and optical results

The Jovian ring is not detectable in Voyager 1 radio occultation data, setting the bounds on its optical thickness of 2 × 10 −4 and 5 × 10 −4 at 13‐ and 3.6‐cm wavelengths, respectively. Comparison of results at radio, infrared, and optical wavelengths suggests a population density that either falls more rapidly than the inverse square of the linear size or is sharply bounded in maximum particle size. A fragmentation power law, ∼ a p for a min < a < a max , where a is the particle radius, and power index p between −3 and −4 lead to a minimum size estimate a min ≃1–2 µm. A specific model which is consistent with all observations consists of a power law distribution of lossless or very slightly absorbent Mie scatterers with refractive index near 1.62, power law index p approximately −3.5, and a minimum particle size or about 1.5 µm. In this model the upper size limit a max is not critical, provided that it is greater than about 4 µm.