31st Annual Meeting of the DPS, October 1999
Session 73. Outer Planet Physics I
Contributed Oral Parallel Session, Friday, October 15, 1999, 2:00-3:20pm, Sala Kursaal

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[73.07] Search for ionospheric winds in Jupiter from the H3+ emissions

J.P. Maillard (IAP, Paris), E. Lellouch (Obs. Meudon), H. Waite, Jr. (SWRI), B. B\'ezard, P. Drossart (Obs. Meudon), J.Y. Mandin, V. Dana (LPMA, Paris)

Between October 8 and 11, 1998, we observed the Northern and Southern auror= al regions of Jupiter in the \nu2 fundamental band of H3+ with the Fourier Transform Spectrometer at CFHT. In total, 15 spectra were recorded.=

The spectra, which covered the 2465--2580 cm-1 domain, were all acquired at a resolving power in the range 55000 to 75000. This high=

resolution, which corresponds to a 4--5.5 km s-1 velocity resolution, = was aimed at searching for ionospheric winds from measurements of Doppler shifts in the H3+ lines. In the brightest regions, up to 20 H3+ lines were detectable, but in practice, about ten lines were usable, including the strongest ones at 2509.075 and 2529.724 cm-1. The S/N ratio on these lines in the spectra set varies=

from 140 to 15, depending on the observed auroral regions. The spectra were=

acquired with a 2.5'' aperture successively centered on specific high latit= ude (57\circ--82\circ) points, either near central meridian or on the=

limbs. Systematic corrections include the topocentric velocity of Jupiter, = the rotational velocity of the target emitting regions, and known instrumental=

effects. The estimated accuracy is on the order of 1 km s-1, one major source o= f uncertainty coming from the pointing precision. Current results marginally =

indicate the presence of ~ 2 km -1 retrograde winds on the Jupite= r North and South Eastern limbs, and possibly a radial component of comparable amplitude on the central meridian. From this first analysis, the order of magnitude of the measured winds is=

consistent with the results of Rego et al. (Nature, 1999), hence excluding=

ionospheric Jovian winds at the altitude of H3+ formation faster than 3 km s-1.

The author(s) of this abstract have provided an email address for comments about the abstract: maillard@iap.fr

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