Hybrid simulations of stellar wind interaction with close-in extrasolar planets

Kurzfassung

A hybrid code has been used for three-dimensional simulations of the stellar wind interaction with the ionosphere of an Earth-sized close-in extrasolar planet. The hybrid code treats electrons as a massless, charge-neutralizing, adiabatic fluid while ions are treated as macroparticles. To study the effects of an expanding ionosphere, a consequence of an expanding atmosphere as for e.g. exoplanet HD 209458 b, we have compared the simulation results for an ordinary stationary ionosphere with the results for an expanding ionosphere. In both cases we can identify bow shock, magnetopause and ion-composition boundary. The expanding ionosphere pushes the bow shock and magnetopause upstream and increases the size of the entire interaction region, creating a large wake behind the planet dominated only by the expanding ionosphere.