Impact of Star Flare Activity on the Structure of the Hydrogen–Helium Upper Atmosphere of Hot Jupiter

In the paper, the impact of a stellar flare on the upper atmosphere of hot Jupiter has been studied using 1D aeronomic model. The atmosphere has been assumed to have a hydrogen–helium chemical composition, and calculations have been carried out for hot Jupiter HD 209458b. We have examined single and repeated flares, in which the flux of hard UV radiation has increased by 10, 100, and 1000 times compared to the quiescent state of the star. The active phase of the dynamic response of the atmosphere has lasted 12–15 h after the flare, and the characteristic period of relaxation to the initial state has been about a day. From the obtained results, it follows that the flare activity of solar-type stars has not had a significant effect on the evolution of the planetary atmospheres of hot Jupiters. However, the interpretation of transit observations of the disturbed atmospheres of hot Jupiters will make it possible to separate from each other the observational effects associated with the interaction of stellar flares and coronal mass ejections with the upper atmospheres and envelopes of these planets. This will make it possible to determine more accurately the parameters of the stellar wind and coronal mass ejections of solar-type parent stars.