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E. Raynaud, P. Drossart, B. Sicardy (DESPA, Obs. Paris-Meudon), W.B. Hubbard (LPL, Univ. of Arizona), K. Matcheva, T. Widemann (DESPA,Obs. Paris-Meudon), P. Bastien, R. Doyon, D. Nadeau (Phys. Dpt, Univ. of Montreal)
On October, 10th 1999, the northern polar region of Jupiter occulted the bright Hipparcos star HIP 9369 (K=6.7). We observed this occultation in the near IR, at 0.9, 2.2 and 2.4 \mum, from 4 different locations in North and South America (Mount Megantic Observatory in Canada, Kitt Peak and Catalina Observatories in Arizona, and VLT in Chile). The four lightcurves show strong peaks during ingress and egress that are interpreted as fluctuations in the temperature profiles, possibly caused by gravity wave propagation in the planet atmosphere. The comparison of the three North-American curves show striking similarities, especially for Catalina and Kitt Peak curves, which are located only 30km apart projected on the Jovian limb.
We perform a time-analysis of the ingress and egress curves, using a continuous wavelet decomposition of the signal and we study the correlations between the curves from each observatory at different scales. We find very good correlations between Kitt Peak and Catalina curves for several different groups of peaks in the immersion lightcurves, which we interpret as signatures of several gravity waves packets propagating in Jupiter's atmosphere. From the time lags between the peaks, the directions of propagation of these packets are also deduced. The power spectra of the lightcurves as a function of the decomposition scale can be estimated.
We then invert the lightcurves to obtain the temperature profiles and we apply a similar scale-altitude analysis to calculate the power spectra of these temperature profiles, that can be compared to the universal spectrum of gravity-wave driven temperature fluctuations (Smith et al., 1987, J.Atm.Sci., 44,1404-1410).