Transport and Mixing in Jupiter's Stratosphere Inferred from Comet S-L9 Dust Migration

We use a series of 230-nm wavelength images acquired with the Hubble Space Telescope Wide Field and Planetary Camera 2 to trace the spreading of debris introduced into Jupiter's stratosphere by the impact of Comet Shoemaker-Levy 9. Impact debris was transported rapidly equatorward by stratospheric winds from the impact latitude at -45° to at least -20° during the 3.2-year period covered by the observations. We use the observations to test the formulation of mixing and transport in two-dimensional (latitude-height) models for the jovian stratosphere. Two different models for the transport are considered. In the first model, advection by the residual circulation of Westet al.(1992,Icarus100, 245-259) is taken to be the sole transport mechanism. We find that this circulation advects the debris slowly poleward, in disagreement with the observations. In the second model, horizontal diffusive transport by large-scale quasi-geostrophic eddies is also included. The horizontal eddy diffusion coefficients (K_yy) are derived from a map of annual-average Eliassen-Palm flux divergence produced by Westet al.(1992). Introduction of the derived K_yyinto the dynamical model causes a rapid spreading of the debris in both the equatorward and the poleward directions. We find that the predicted rate of equatorward spreading of the impact debris optical depth is in good agreement with that derived from the observations. We conclude that our derived eddy K_yyprovides a useful first-order description of zonal mean eddy transport at mid-latitudes in the southern hemisphere of Jupiter's stratosphere.