Effect of the Star Extreme Radiation Flux on the Structure of the Hydrogen–Helium Upper Atmosphere of Hot Jupiter

In the paper, the structure of the hydrogen–helium upper atmosphere of hot Jupiter depending on the flux of extreme ultraviolet radiation from the host star has been studied. An aeronomic 1D model based on the approximation of single-fluid multicomponent hydrodynamics has been used for calculations. The numerical model has taken into account chemical reactions, heating-cooling processes, tidal action from the star, diffusion, and thermal conductivity. Calculations have been performed for hot Jupiter HD 209458b. In all the obtained solutions, a transonic planetary wind has been formed leading to a hydrodynamic outflow of the atmosphere. Taking into account the tidal force has led to increase the outflow of atmosphere by 2.5 times compared to the case, in which only the gravity of the planet has been considered. The dependence of the mass loss rate of the planet on the flux of extreme ultraviolet radiation has been found to be nonlinear. This may be due to a different dominant mechanism of conversion of absorbed radiant energy in the upper atmosphere within the limits of weak and strong ultraviolet fluxes.