HR: 1330h
AN: P12A-1049    [PDF]
TI: Monitoring Jupiter's Atmosphere for Tidal Oscillations
AU: * Houben, H
EM: houben@humbabe.arc.nasa.gov
AF: Bay Area Environmental Research Institute, 560 Third Street West, Sonoma, CA 95476 United States
AU: Mosqueira, I
EM: mosqueir@cosmic.arc.nasa.gov
AF: SETI Institute, 2035 Landings Drive, Mountain View, CA 94043 United States
AU: Showman, A
EM: showman@lpl.arizona.edu
AF: University of Arizona, Lunar and Planetary Lab., Tucson, AZ 85721 United States
AU: Young, R E
EM: Richard.E.Young@nasa.gov
AF: NASA Ames Research Center, MS 245-3, Moffett Field, CA 94035 United States
AB: Tidal dissipation in Jupiter is the ultimate source of the energy that powers Io's volcanism and may also be an important cause of heating in Europa and Ganymede. However, the mechanism of jovian tidal dissipation is still unknown. In general, there are two possibilities that can work in a fluid planet: 1) some viscous process in the interior of the planet (although eddy viscosity due to convective overturning can be excluded because of the large mismatch between the tidal period and the convective eddy timescale); or 2) the generation of inertia-gravity waves (a natural consequence of tidal forcing in any stably stratified fluid) that propagate to the upper atmosphere before breaking. Our calculations rule out the possibility that a stable, resonant, ducting layer in the atmosphere or outer envelope of Jupiter would result in large wave amplitudes and dissipate enough energy to account for a longterm average tidal dissipation factor (Q) of $10^5$. But, we cannot exclude the possibility that a stable layer (perhaps due to composition gradients) in the deep interior would have this effect. The resulting energy flux ($\sim 10^{21}$ erg/s) would be an important factor in the thermospheric heat balance. Thus, by monitoring Jupiter's atmosphere to determine the amplitude of the tidal wave response, JIMO would contribute to the understanding of the longterm orbital and thermal evolution of the Galilean satellites, while also shedding light on Jupiter's interior structure and upper atmospheric heat balance. Even a negative result would be valuable. Although global jovian atmospheric oscillations have been difficult to observe, the fact that we know the tidal frequencies and wavenumbers exactly will make it possible to add even random or opportunistic observations in phase to enhance the desired signal. We estimate that the waves will have a temperature amplitude less than 1 K, but a horizontal wind amplitude of up to 10 m/s at the 100 mbar level of the atmosphere.
DE: 5707 Atmospheres--structure and dynamics
DE: 5770 Tidal forces
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting