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

Abstract

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 agree 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 et al. 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 et al. The portion of the vanguard ejected closer to the vertical falls back with high zcomponent 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.

Impact flux on Jupiter: From superbolides to large-scale collisions

“…The parameters in the EOS for our ice impactor are identical to those listed in Korycansky et al (2006). The Jovian atmosphere is modeled by a temperaturepressure profile that is adopted from Deming & Harrington (2001). The impactor is initially introduced at z = 150 km altitude (x 1 distances indicate along-track values, z values represent altitude above the 1 bar pressure level).…”

Jupiter’s stratospheric hydrocarbons and temperatures after the July 2009 impact from VLT infrared spectroscopy

“…Indeed, the 2009 plume may never have left the influence of frictional drag, and particulate trajectories cannot be regarded as truly unimpeded. Given that the shock front penetrated to at least 1 bar (from enhanced NH 3 over the impact streak, Fletcher et al 2010), the shallow entry angle implies that the rising plume would have needed to travel over much greater distances to reach the microbar pressures of the SL9 shock fronts (e.g., Deming & Harrington 2001), and would have been prone to greater frictional dissipation as it travelled through the collapsing entry column (Palotai, pers. comm.…”

“…Models of the comet Shoemaker Levy 9 impacts in 1994 (SL9, see Harrington et al 2004, and references therein) predict two sources of atmospheric heating: (a) kinetic energy in the heated entry channel from the incoming bolide, being disrupted and vaporised as it fell to its terminal depth; and (b) heating from the compression shock wave as the ballistic plume of material re-entered the atmosphere (Crawford 1996;Mac Low 1996;Deming & Harrington 2001). The material in the plume was a complex mixture of reprocessed material from the impactor, the unique chemical products from the shock heating of the jovian air and entrained jovian gases from the deeper troposphere (Lellouch 1996;Zahnle 1996).…”

Fragmentation modelling of the 2019 August impact on Jupiter

“…We use C D = 0.92 (Carter et al 2009), g = 24.0 m/s, R p = 70000 km as fixed constants for all test cases. The atmospheric density profile was constructed by solving the hydrostatic balance given the temperature-pressure profile adapted from Deming & Harrington (2001) (Fig 6a) and assuming a dry atmosphere with a constant molar mass of M atmo = 2.28. The corresponding density profile is shown in Fig 6b . By convention, h = 0 corresponds to the 1 bar pressure level.…”