JOVIAN SYSTEM DATA ANALYSIS PROGRAM PROPOSAL SUMMARY

GENERAL SCIENTIFIC OBJECTIVES: The scientific objectives of the proposed research are to investigate a broad range of fundamental problems in atmospheric chemistry, dynamics, and radiation pertinent to the atmospheres of the giant planets, and their satellites. The goals are to understand the global structures of their composition, pressure, temperature, and winds. The proposed research will advance our knowledge of the giant planets and their satellites, provide interpretation of data acquired from Pioneer, Voyager, Galileo, Hubble Space Telescope (HST), and support planning for other missions to the outer planets.

SPECIFIC SCIENTIFIC OBJECTIVES: The proposed research will focus on gravity wave properties and effects in the Jupiter's upper atmosphere. The relevant data sets are those from the ASI instrument on the Galileo probe and the ionospheric electron density profiles obtained from radio occultations performed from the Galileo orbiter. The latter contain sharp ionization layers of sporadic E-layer character that gravity waves can produce. Gravity wave properties will be inferred from both data sets and their effects on the plasma and thermal structure of Jupiter's upper atmosphere will be modeled.

ACCOMPLISHMENTS: Heating Jupiter's thermosphere by viscous dissipation of upward propagating gravity waves was evaluated with correct formulations of total energy conservation and the total wave induced vertical energy flux. In contrast to the results of Young et al. (1997), our calculations, with their wave amplitudes and parameters, yield a maximum thermospheric temperature of T = 505 K at 680 km above the 1 bar level in comparison to the Galileo probe inferred temperature of T = 900 K and therefore gravity waves may not be solely responsible for the observed steep temperature gradient just above the homopause. The large sensible heat flux associated with dissipating gravity waves generates net heating of the lower regions and net cooling of the upper regions of wave dissipation due to energy redistribution. The transition from net heating to net cooling occurs at the level of constant wave amplitude. In regions of substantial wave dissipation the local cooling rate due to sensible heat flux divergence can exceed the local heating due to convergence of the Eliassen-Palm flux to produce 1) net cooling of and 2) a distinct temperature decrease (~ 45 K) in the topside thermosphere. To simulate Jupiter's thermospheric temperature profile inferred from the Galileo probe data with 1) gravity wave heating only, 2) 100% conversion of wave energy to internal energy, and 3) radiative cooling by H3+ near-IR emission ~ 0.1 erg cm-2 s-1, gravity waves must deposit their energy high in the thermosphere with peak heating occurring near ~ 1000 km and with near saturation amplitudes at and above these heights.

CITATIONS: Matcheva, K. I., and D. F. Strobel, Heating of Jupiter's thermosphere by dissipation of gravity wavs due to molecular viscosity and heat conduction, Icarus, submitted, 1998.