John Caldwell

H3(+) fundamental band in Jupiter's auroral zones at high resolution from 2400 to 2900 inverse centimeters

Following the previous detection of H3(+) in the southern auroral zone of Jupiter from its 2nu2 band, a search was made for the fundamental at 4 microns. Up to 42 lines of this band were detected in emission, at high resolution, on the auroral spot of each hemisphere. A rotational temperature was derived for the southern and northern zones, respectively, of 1000 + or - 40K and 835 + or - 50 K. The intensity of the lines was on the average two times stronger in the south than in the north. The 2nu2 band, which was sought in the north only on this occasion, was not detectable. A purely thermal mechanism for the H3(+) production is implied. Spatial extension and temporal variability of the excitation is discussed. 20 refs.

Semi-annual oscillations in Saturn's low-latitude stratospheric temperatures.

Observations of oscillations of temperature and wind in planetary atmospheres provide a means of generalizing models for atmospheric dynamics in a diverse set of planets in the Solar System and elsewhere. An equatorial oscillation similar to one in the Earth’s atmosphere has been discovered in Jupiter. Here we report the existence of similar oscillations in Saturn’s atmosphere, from an analysis of over two decades of spatially resolved observations of its 7.8-μm methane and 12.2-μm ethane stratospheric emissions, where we compare zonal-mean stratospheric brightness temperatures at planetographic latitudes of 3.6° and 15.5° in both the northern and the southern hemispheres. These results support the interpretation of vertical and meridional variability of temperatures in Saturn’s stratosphere as a manifestation of a wave phenomenon similar to that on the Earth and in Jupiter. The period of this oscillation is 14.8u2009±u20091.2 terrestrial years, roughly half of Saturn’s year, suggesting the influence of seasonal forcing, as is the case with the Earth’s semi-annual oscillation.

Line-resolved spectroscopy of the Jovian H3+ auroral emission at 3.5 micrometers

High-resolution line-resolved spectra of the auroral regions of Jupiter at 3.5 μm have been obtained in 1992 March at the Canada-France-Hawaii Telescope. From the width of H 3 + lines, a translational temperature of 1150 K±60 K is measured, quite comparable to the rotational temperature of 1250 K±70 K measured from the relative intensities of the same lines. These measurements confirm that the rotational temperatures previously measured on Jupiter from 2 and 4 μm rovibrational bands of H 3 + are consistent with a high kinetic temperature of the ionosphere