A self-consistent model of the Jovian auroral thermal structure

A one-dimensional (1-D) model coupling a two-stream electron transport mode l of energy deposition with a 1-D thermal conduction model has been develop ed. It is applied to investigate the links between auroral heat input and t he vertical temperature of Jupiter's upper atmosphere. Two energy distribut ions meant to reproduce the emissions of a diffuse and a discrete aurora ar e used to evaluate the importance of the energy spectrum of the incident el ectrons for the thermal balance of Jupiter's auroral thermosphere. The valu es of observable quantities such as the altitude of the H-2 emission peak, thermal infrared (LR), ultraviolet (UV) emissions, and temperatures associa ted with various optical signatures are used to constrain the parameters of these distributions. It is shown that the high-energy component of these e nergy distributions heats a region of the homosphere between 10(-4) and 10( -6) bar and mainly controls the H-2 temperature and the far-UV (FUV) emissi on. A 3-keV soft electron component is necessary to heat the region directl y above the homopause, between 10(-6) and 10(-9) bar. It has a large influe nce on the H-2 and H-3(+) temperatures and on the H-3(+) near-IR(NIR) emiss ion. It is used in conjunction with a weak 100 eV component which is respon sible for heating the thermosphere, from 10(-9) to 10(-12) bar and exerts a control on the exospheric temperature. The calculated temperatures, UV, an d IR emissions suggest that the model probably misses a nonparticle heat so urce in the 10(-5) bar region, that is expected to balance the strong hydro carbon cooling. Sensitivity tests are performed to evaluate the importance of the parameters of the energy distributions. They show that the FUV color ratio increases with the characteristic energy (or high-energy cutoff) of the high-energy component, while the H-2 rovibrational temperature varies i nversely. A trade-off is therefore necessary for these two parameters to si multaneously meet their observational constraints. Further tests demonstrat e the essential thermostatic role played by H-3(+), which regulates the net heating in the thermosphere. An increased eddy diffusion reproduces the ef fect of a possible auroral upwelling of methane but gives rise to an H-2 te mperature smaller than the observed value.