“Weather” Variability Of Close-in Extrasolar Giant Planets

Astrophysics, abstract
astro-ph/0210499

From: Kristen Menou <km5yj@astsun.astro.virginia.edu>

Date: Tue, 22 Oct 2002 21:25:11 GMT   (15kb)

“Weather” Variability Of Close-in Extrasolar Giant Planets

Shallow-water numerical simulations show that the atmospheric circulation of
the close-in extrasolar giant planet (EGP) HD 209458b is characterized by
moving circumpolar vortices and few bands/jets (in contrast with ~10 bands/jets
and absence of polar vortices on Jupiter and Saturn). The large spatial scales
of moving circulation structures on HD 209458b may generate detectable
variability of the planet’s atmospheric signatures. In this Letter, we
generalize these results to other close-in EGPs, by noting that shallow-water
dynamics is essentially specified by the values of the Rossby (Ro) and Burger
(Bu) dimensionless numbers. The range of likely values of Ro (~ 0.01 – 10) and
Bu (~ 1 – 200) for the atmospheric flow of known close-in EGPs indicates that
their circulation should be qualitatively similar to that of HD 209458b. This
results mostly from the slow rotation of these tidally-synchronized planets.

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