Characterizing exoplanet upper atmosphere-plasma environments by observations and modelling techniques
Space Research Institute
Austrian Academy of Sciences
For the analyzing of stellar plasma flows around planetary magnetospheres Energetic Neutral Atom (ENA) imaging have become an important remote-sensing tool in planetary science. ENAs are produced whenever solar- or stellar wind protons interact via charge exchange with a neutral particle from an upper atmosphere of a planetary body so that their signals constrain both, ion distributions and neutral gas densities. In this study ENA-observations and data interpretations of hydrogen-cloud observations in UV Lyman-α absorption around hydrogen-rich exoplanet HD 209458b is presented. It is discussed how these observations together with numerical models can be used for the study of the upper atmosphere structure of planets, the planetâ€™s magnetospheric shape and information on stellar wind properties. Futher study results are presented showing that our proposed technique can also be applied to terrestrial exoplanets within orbits of M-stars. Detailed analysis of future observations of hydrogen clouds around Earth-type exoplanets will also enhance our understanding how the atmospheres of terrestrial planets evolved during the extreme phase of the young Sun/young stars.