RADIATIVE TRANSFER AND PHOTOCHEMISTRY IN THE UPPER ATMOSPHERE OF JUPITER

A direct finite difference numerical solution for the equation of radiative transfer is developed for use in planetary atmospheres. The procedure uses a plane-parallel atmosphere, and can treat partial frequency redistribution (for use in the radiative transfer of optically thick resonance lines), inhomogeneity, external or internal sources, and various boundary conditions. A program that utilizes this method is applied to the Lyman-(alpha) aurora, the reflected UV continuum from 1500 (ANGSTROM) to 1740 (ANGSTROM), and the resonantly-reflected He I 584 (ANGSTROM) line of Jupiter.; Detailed modeling of the reflected UV continuum as measured by the International Ultraviolet Explorer reveals the mixing ratios of C(,2)H(,2), C(,2)H(,6), and C(,4)H(,2) to be (1.0 (+OR-) 0.1) x 10('-7), (6.6 (+OR-) 5.3) x 10('-6), and (2.9 (+OR-) 2.0) x 10('-10), respectively in the pressure region between (TURN)3 and 40 mbar on Jupiter. Upper limits in this pressure region for the mixing ratios of C(,2)H(,4) and NH(,3) are; (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI); respectively. An upper limit to the optical depth of dust above the tropopause, assuming it is well mixed, is; (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI); and an upper limit on the dayglow emission by the Lyman bands of H(,2) is; (DIAGRAM, TABLE OR GRAPHIC OMITTED...PLEASE SEE DAI); kiloRayleighs. Study of the resonant scattering of the solar He I 584 (ANGSTROM) emission line by the upper Jovian atmosphere indicates that the homopause eddy diffusion coefficient was 1.3 x 10('6) cm('2) s('-1) (+OR-) 30% at the times of the Voyager encounters and (TURN) 1 x 10('8) cm('2) s('-1) during the Pioneer 10 encounter.; The above results are used as constraints for a one-dimensional photochemical-diffusive model of the hydrocarbon chemistry in Jupiter's upper atmosphere. It is shown that the amount of methane dissociation resulting from acetylene photochemistry is comparable to the amount that is due to direct photolysis. Profiles for the major observed hydrocarbon species are calculated and their sensitivity to eddy diffusion profile, chemistry, and solar UV flux is examined. It is shown that polyacetylene formation driven by acetylene photochemistry in the models presented here is capable of producing the observed abundance of Danielson dust in the Jovian stratosphere. Finally, the problems of auroral chemistry on Jupiter are briefly considered.