The role of H-3(+) in planetary atmospheres

Spectroscopic studies of the upper atmospheres of the giant planets using i nfrared wavelengths sensitive to the H-3(+) molecular ion show that this sp ecies plays a critical role in determining the physical conditions there. F or Jupiter, we propose that the recently detected H-3(+) electrojet holds t he key to the mechanism by which the equatorial plasma sheet is kept, in (p artial) co-rotation with the planet, and that this mechanism also provides a previously unconsidered source of energy that helps explain why the jovia n thermosphere is considerably hotter than expected. For Saturn, we show th at the H-3(+) auroral emission is ca. 1% of that of Jupiter because of the lower ionospheric/thermospheric temperature and the lower flux of ionizing particles precipitated there it is probably unnecessary to invoke additiona l chemistry in the auroral/polar regions. For Uranus, we report further evi dence that its emission intensity is controlled by the cycle of solar activ ity. And we propose that H-3(+) emission may just be detectable using curre nt technology from some of the giant extra-solar planets that have been det ected orbiting nearby stars, such as Tau Bootes.