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 debri s introduced into Jupiter's stratosphere by the impact of Comet Shoemaker-L evy 9. Impact debris was transported rapidly equatorward by stratospheric w inds from the impact latitude at -45 degrees to at least -20 degrees during the 3.2-year period covered by the observations. We use the observations t o test the formulation of mixing and transport in two-dimensional (latitude height) models for the jovian stratosphere. Two different models for the t ransport are considered. In the first model, advection by the residual circ ulation of West et al. (1992, Icarus 100, 245-259) is taken to be the sole transport mechanism. We find that this circulation advects the debris slowl y poleward, in disagreement with the observations. In the second model, hor izontal diffusive transport by large-scale quasi-geostrophic eddies is also included. The horizontal eddy diffusion coefficients (K-yy) are derived fr om a map of annual-average Eliassen-Palm flux divergence produced by West e t al. (1992). Introduction of the derived K-yy into the dynamical model cau ses a rapid spreading of the debris in both the equatorward and the polewar d directions. We find that the predicted rate of equatorward spreading of t he impact debris optical depth is in good agreement with that derived from the observations. We conclude that our derived eddy K-yy provides a useful first-order description of zonal mean eddy transport at mid-latitudes in th e southern hemisphere of Jupiter's stratosphere. (C) 1999 Academic Press.