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P. Gaulme, B. Mosser (LESIA)
First studies about Jovian oscillations are due to Vorontsov et al. (1976). Attempts to observe them started in the late 1980's (Deming et al. 1989, Mosser et al. 1991). The micro-satellite Jovis and ground-based observations campaign such as SŸMPA (e.g Baglin et al. 1999) account for an accurate analysis of the cloud response to an acoustic wave. Therefore, the propagation of sound or gravity waves in the Jovian troposphere is revisited, in order to estimate their effect on the highest clouds layer.
From basic thermodynamics, the troposphere should be stratified in three major ice clouds layers: water-ammonia, ammonium-hydrosulfide and ammonia ice for the highest. The presence of ammonia ice clouds has been inferred from Kuiper in 1952, and was predicted to dominate the Jovian skies. However, they had been observed spectroscopically over less than one percent of the surface. This absence of spectral proof could come from a coating of ammonia particles from other substances (Baines et al. 2002).
In this work, we study the behaviour of a cloud submitted to a periodic pressure perturbation. We suppose a vertical wave propagating in a plane parallel atmosphere including an ammonia ice cloud layer. We determine the relation between the Lagrangian pressure perturbation and the variation of the fraction of solid ammonia. The linearized equations governing the evolution of the Eulerian pressure and density perturbed terms allows us to study how the propagation is altered by the clouds and how the clouds move with the wave. Finally, because a pressure perturbation modifies the fraction of solid ammonia, we estimate how much an ammonia crystal should grow or decrease and how the clouds albedo could change with the wave.
Baglin et al. 1999. BAAS 31, 813.
Baines et al. 2002. Icarus 159, 74.
Deming et al. 1989. Icarus 21, 943.
Kuiper 1952. The atmospheres of the Earth and Planets pp. 306-405. Univ. of Chicago Press, Chicago.
Mosser et al. 1991. A&A 251, 356.
Vorontsov et al. 1976. Icarus 27, 109.
The author(s) of this abstract have provided an email address for comments about the abstract: Patrick.Gaulme@obspm.fr
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.