On the Temperature of the Jovian Thermosphere

Abstract

A theoretical study is made to assess the importance of the solar EUV flux in the thermal energy balance of the Jovian thermosphere. A global averaged vertical temperature contrast in the thermosphere of 15K is calculated and the mesopause is located at a particle density of 5?1013 cm?3. Thus, the upper atmosphere of Jupiter is approximately isothermal. At the mesopause IR cooling by C3H2 is an order of magnitude more important than IR cooling by CH4. Only the location of the mesopause is a sensitive function of the IR cooling agent in the upper atmosphere. The exospheric temperature depends principally on the mesopause temperature and the solar flux. Eddy heat transport plays a negligible role in the thermal energy balance of the Jovian thermosphere. For the thermospheres of Saturn and Titan the global averaged vertical temperature contrasts are estimated to be ?10K and 90K, respectively, if their compositions are similar to Jupiter's and the same physics is applicable.