Models of the Shoemaker-Levy 9 Impacts. II. Radiative-Hydrodynamic Modeling of the Plume Splashback

We model the plume "splashback" phase of the Shoemaker-Levy 9 (SL9) collisions with Jupiter. We modified the ZEUS-3D hydrodynamic code to include radiative transport in the gray approximation and present validation tests. After initializing with a model Jovian atmosphere, we couple mass and momentum fluxes of SL9 plume material, as calculated by the ballistic Monte Carlo plume model of Paper I of this series. A strong and complex shock structure results. The shock temperatures produced by the model agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high-excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agrees with observations over a broad wavelength range (0.9-12 μm). Much of the complex structure of these light curves is a natural consequence of the temperature dependence of the Planck function and the plume velocity distribution. A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the "vanguard." Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the "third precursors" seen in the 2 μm light curves of the larger impacts and for hot methane emission at early times observed by Dinelli and coworkers. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3-4 μm by McGregor and coworkers. The portion of the vanguard ejected closer to the vertical falls back with high z-component velocities just after maximum light, producing CO emission and the "flare" seen at 0.9 μm. The model also produces secondary maxima ("bounces"), whose amplitudes and periods are in agreement with observations.