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E. Garcia-Melendo (Esteve Duran Obs. Foundation, Seva, Spain), A. Sánchez-Lavega (U. Pais Vasco, Bilbao, Spain), T. E. Dowling (U. Louisville)
In 1990 a disturbance developed in the strongest Jovian jet located at ~24ºN (Sanchez-Lavega et al., Icarus, Vol 94, 92-97, 1991). At the onset of the disturbance, two bright spots, most probably clouds of convective origin with an initial length scale ~6000 km, appeared on the peak of the 24ºN jet stream. Over the next weeks and to the west of these high albedo features, chains of low albedo spots developed showing a regular dark/light pattern, suggesting a trailing wave disturbance. After the dark spot outbreak seven anticyclonic vortices, located a few tenths of degree to the south of the 24ºN jet, survived for a period of 10 years (Garcia-Melendo et al., Icarus, Vol 146, 514-524, 2000). In order to try to understand the origin and evolution of all the observed phenomena and morphology in that region of Jupiter, computer simulations were carried out using the Explicit Planetary Isentropic Coordinate (EPIC) model (Dowling, Icarus, Vol 132, 221-238, 1998). Different vertical temperature and wind profiles, down to the 6 bar altitude level, were tested in order to simulate the observed disturbance behavior. We found that when the jet has the highest speed of 180 m/s, slightly increasing in depth, a Gaussian heat pulse simulating the bright spot outbreak is able to generate, during the first four weeks, a low frequency wave disturbance which propagates in the upstream direction with respect to the jet stream peak velocity, as observed in the real 1990 disturbance, evolving finally into the observed chain of anticyclonic vortices. The low frequency of the resulting waves in our simulations implies these are Rossby waves. Results also indicate that the trailing chains of dark features progressively merge to form the long-lived vortices that have the observed size and aspect ratio, and move at the observed velocity
This work was supported by the Spanish MCYT PNAYA 2000-0932, by Grupos UPV/EHU, and by the Esteve Duran Observatory Foundation in Seva. It also made use of the computing facilities at CESCA in Barcelona.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.