CHANGING FACE OF THE EXTRASOLAR GIANT PLANET, HD 209458b

High-resolution atmospheric flow simulations of the tidally-locked extrasolar giant planet, HD209458b, show large-scale spatio-temporal variability. This is in contrast to the simple, permanent day/night (i.e., hot/cold) picture. The planet’s global circulation is characterized by a polar vortex in motion around each pole and a banded structure corresponding to ∼3 broad zonal (east-west) jets. For very strong jets, the circulation-induced temperature difference between moving hot and cold regions can reach up to ∼1000 K, suggesting that atmospheric variability could be observed in the planet’s spectral and photometric signatures. subject headings: planetary systems – planets and satellites: general – stars: atmospheres – turbulence