Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 2G021

Influence of the interaction between stellar wind plasma and upper atmospheres on the evolution of the exoplanet

Kislyakova, Kristina (Space Research Institute, Austrian Academy of Sciences, Graz, Austria)
Lammer, Helmut (Space Research Institute, Austrian Academy of Sciences, Graz, Austria)
Erkaev, Nikolai (Institute of Computational Modelling, Siberian Division of Russian Academy of Sciences, Krasnoyarsk, Russian Federation)
Holmström, Mats (Swedish Institute of Space Physics, Kiruna, Sweden)
Odert, Petra (Space Research Institute, Austrian Academy of Sciences, Graz, Austria; Institute for Physics, University of Graz, Austria)
Khodachenko, Maxim (Space Research Institute, Austrian Academy of Sciences, Graz, Austria)
Kulikov, Yuri (Polar Geophysical Institute, Russian Academy of Sciences, Murmansk, Russian Federation)
Güdel, Manuel (Institute for Astrophysics, University of Vienna, Austria)

Interaction between stellar wind plasma and the upper atmosphere of the exoplanets plays a significant role in their evolution. Together with the present or absent planetary dynamo, evolving stellar radiation and wind conditions influence the intensity of the interaction processes. The most intensive interaction is expected in systems of non- or weakly magnetized planets which are located close to an active host star. The influence of the star can be divided in two main aspects: high radiation level in the XUV branch (extreme ultraviolet and soft X-ray) causes the expansion and heating of the upper atmosphere leading in some cases even to the blow-off state. During blow-off the atmosphere is not hydrostatic anymore and expands upwards, undergoing extremely strong thermal escape. The second aspect consists in non-thermal erosion processes: even if the atmosphere is still hydrostatic, fast and dense stellar wind of a young active star may erode it effectively leading to ionization and subsequent ion escape, especially strong if the planet’s magnetic field is weak or the exosphere expands above the magnetopause. In the presented investigation both, thermal escape and non-thermal ion pickup together with attendant processes are studied. Escape rates, their dependence on various conditions and change during the system’s history are determined. As an example we consider a hypothetical Earth-like planet and a ”Super-Earth” both located in the habitable zone of an M dwarf (Gliese 436 is taken as a proxy).

Click here to view poster PDF