Coronal Mass Ejections (CMEs) may play a crucial role for non-thermal atmospheric mass loss of hot Jupiters which are located between 0.02 – 0.045 AU. In a recent study by Lammer et al. (2009) the authors found that non-thermal stellar plasma induced H+ pick up erosion of a non- or weakly magnetized “Hot Jupiter” is most likely negligible if such a planet interacts with the ordinary stellar wind or average CMEs. Due to a large stellar EUV flux, extended ionospheres are produced. The ion pressure in these ionospheres is strong enough, so the stellar wind and CME ram pressure can be balanced at distances of a few planetary radii, resulting in negligible atmospheric erosion rates over evolutionary time scales. Fast CMEs however, cannot be balanced by the planetary ion pressure at orbital distances between 0.02–0.1 AU. During such collisions “Hot Jupiters” may experience high non-thermal escape rates.
Future research on fast CME interaction with “Hot Jupiters” will help us to understand if such extreme events are behind the phenomenon that no gas giants with masses < 1.0MJup are discovered so far at orbital distances ≤ 0.035 AU. Finally we conclude that the results of our study show that the discovery of transiting exoplanets at orbital distances ≤ 0.015 AU and ground-based follow-up mass determinations together with theoretical mass loss studies can bring reliable information on the statistics of remaining cores of shrinked gas giants.
