Aeronomic Model of Hydrogen-Helium Upper Atmospheres of Hot Giant Exoplanets

The paper presents a one-dimensional aeronomic model of hydrogen-helium upper atmospheres of hot giant exoplanets based on the approximation of single-fluid multicomponent hydrodynamics. Chemical reactions and heating-cooling processes are taken into account. Typical cases of a hot Jupiter and a warm Neptune are considered as an example of the application of the model. Calculations were carried out for various values of the gas pressure at the photometric radius of a planet. In the solutions obtained, the transonic planetary wind is formed, which leads to a hydrodynamic outflow of the atmosphere with mass loss rates of about 3.5X10(10) and 3.7X10(9) g/s for a hot Jupiter and a warm Neptune, respectively. At the same time, the outer layers of the atmosphere of a hot Jupiter become completely ionized, while the atmosphere of a warm Neptune mainly consists of neutral gas. In some variants of the hot Jupiter model, instability develops in the deep layers of the atmosphere, which may result in the formation of a specific cloud layer.