Speaker
Description
The evolution of planetary atmospheres is very much dependent on the environment of their host stars (e.g., stellar radiation, stellar wind, stellar flares and Coronal Mass Ejections (CMEs)). For close-in planets, the stellar radiation evaporates the planetary atmosphere as a form of supersonic planetary outflow due to photoionization. This planetary outflow further interacts with the stellar wind, which shapes up the planetary atmosphere (sometimes producing a comet-like structure) and its mass loss rate. Moreover, flares and CMEs from the star will also have a great impact on planetary evaporation. In this talk, I will discuss the effect of stellar wind, and the impact of flares and CMEs on the atmosphere of hot Jupiters using a self-consistent 3D radiation hydrodynamic model. Among all the considered stellar environments, we find that CMEs are very effective in eroding planetary atmospheres. We also calculate synthetic Lyman-alpha transit signatures and find that the flare alone cannot explain the observed high blue shifted velocities seen in the Lyman-alpha observation. The CME, however, leads to an increase in the velocity of the escaping atmosphere, enhancing the transit depth at high blue shifted velocities. Finally, I will also discuss the effect of the different orientations of the CME magnetic field on the atmospheric escape and corresponding transit signatures.
