Atmospheric circulation and tides of "51 Pegasus b-like" planets

Adam Showman, T. Guillot

Research output: Contribution to journalArticle

333 Citations (Scopus)

Abstract

We examine the properties of the atmospheres of extrasolar giant planets at orbital distances smaller than 0.1 AU from their stars. We show that these "51 Peg b-like" planets are rapidly synchronized by tidal interactions, but that small departures from synchronous rotation can occur because of fluid-dynamical torques within these planets. Previous radiative-transfer and evolution models of such planets assume a homogeneous atmosphere. Nevertheless, we show using simple arguments that, at the photosphere, the day-night temperature difference and characteristic wind speeds may reach ∼500 K, and ∼2 km s-1, respectively. Substantial departures from chemical equilibrium are expected. The cloud coverage depends sensitively on the dynamics; clouds could exist predominantly either on the dayside or nightside, depending on the circulation regime. Radiative-transfer models that assume homogeneous conditions are therefore inadequate in describing the atmospheric properties of 51 Peg b-like planets. We present preliminary three-dimensional, nonlinear simulations of the atmospheric circulation of HD 209458b that indicate plausible patterns for the circulation and generally agree with our simpler estimates. Furthermore, we show that kinetic energy production in the atmosphere can lead to the deposition of substantial energy in the interior, with crucial consequences for the evolution of these planets. Future measurements of reflected and thermally-emitted radiation from these planets will help test our ideas.

Original languageEnglish (US)
Pages (from-to)166-180
Number of pages15
JournalAstronomy and Astrophysics
Volume385
Issue number1
StatePublished - Apr 2002

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atmospheric tides
atmospheric tide
atmospheric circulation
planets
planet
atmospheres
radiative transfer
atmosphere
photosphere
torque
night
kinetic energy
chemical equilibrium
temperature gradients
wind velocity
stars
orbitals
fluid
fluids

Keywords

  • Planets and satellites: general
  • Stars: planetary systems

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Atmospheric circulation and tides of "51 Pegasus b-like" planets. / Showman, Adam; Guillot, T.

In: Astronomy and Astrophysics, Vol. 385, No. 1, 04.2002, p. 166-180.

Research output: Contribution to journalArticle

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