The Atmospheric Wind of Hot Exoplanets and its Manifestations in Observations: from Energy Estimates to 3D MHD Models

The studies of close-orbit gaseous exoplanets—hot Jupiters and warm Neptunes—are reviewed. Transit spectral observations of the Hubble Space Telescope stimulated the numerical modeling of these objects. The supersonic outflow of the upper atmosphere of hot exoplanets and its interaction with the stellar plasma flow is a newly-discovered phenomenon in plasma physics and astrophysics that pools photo- and plasma-chemistry, collision-induced gas-dynamics, and collisionless space plasma. Starting from 2003, the modeling of physical processes in this field has considerably developed from simple quasi-empiric analytical formulas to global three-dimensional magnetic hydrodynamic (3D MHD) codes. The attained level makes it possible to interpret the in-transit measurements in absorption lines of different elements and estimate the parameters of both the planetary atmospheres and the stellar plasma wind.