“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 to ~10 bands/jets and the absence of polar vortices on cloud-top 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 (~10-2 to 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.

[1]  P. Rhines.  Waves and turbulence on a beta-plane , 1975, Journal of Fluid Mechanics.

[2]  L. Polvani,et al.  The Morphogenesis of Bands and Zonal Winds in the Atmospheres on the Giant Outer Planets , 1996, Science.

[3]  I. Baraffe,et al.  Theory of Low-Mass Stars and Substellar Objects , 2000 .

[4]  Zucker,et al.  The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458. , 2000, The Astrophysical journal.

[5]  J. Holton.  Geophysical fluid dynamics. , 1983, Science.

[6]  S. Seager,et al.  Extrasolar Giant Planets under Strong Stellar Irradiation , 1998 .

[7]  L. Polvani,et al.  The emergence of jets and vortices in freely evolving, shallow-water turbulence on a sphere , 1996 .

[8]  David Charbonneau,et al.  Hubble Space Telescope Time-Series Photometry of the Transiting Planet of HD?209458 , 2001 .

[9]  T. Brown.  Transmission Spectra as Diagnostics of Extrasolar Giant Planet Atmospheres , 2001, astro-ph/0101307.

[10]  Sara Seager,et al.  The Changing Face of the Extrasolar Giant Planet HD 209458b , 2002, astro-ph/0209227.

[11]  J. Holton.  An introduction to dynamic meteorology , 2004 .

[12]  R. Gilliland,et al.  Detection of an Extrasolar Planet Atmosphere , 2001, astro-ph/0111544.

[13]  Adam Burrows,et al.  ALBEDO AND REFLECTION SPECTRA OF EXTRASOLAR GIANT PLANETS , 1999 .

[14]  木村 竜治,et al.  J. Pedlosky: Geophysical Fluid Dynamics, Springer-Verlag, New York and Heidelberg, 1979, xii+624ページ, 23.5×15.5cm, $39.8. , 1981 .

[15]  Marley,et al.  On the Radii of Close-in Giant Planets , 2000, The Astrophysical journal.

[16]  Tristan Guillot,et al.  Astronomy and Astrophysics Evolution of " 51 Peg B-like " Planets , 2001 .

[17]  J. Pedlosky.  Geophysical Fluid Dynamics , 1979 .

[18]  T. Brown,et al.  Detection of Planetary Transits Across a Sun-like Star , 1999, The Astrophysical journal.

[19]  Princeton,et al.  Theoretical Transmission Spectra during Extrasolar Giant Planet Transits , 1999, astro-ph/9912241.

[20]  R. P. Butler,et al.  A Transiting “51 Peg-like” Planet , 2000, The Astrophysical journal.

[21]  Tristan Guillot,et al.  Atmospheric circulation and tides of ``51 Pegasus b-like'' planets , 2002 .

[22]  S. Seager,et al.  PHOTOMETRIC LIGHT CURVES AND POLARIZATION OF CLOSE-IN EXTRASOLAR GIANT PLANETS , 2000 .

[23]  S. Jha,et al.  Multicolor Observations of a Planetary Transit of HD 209458 , 2000, astro-ph/0007245.