MID-TO-LOW LATITUDE H-3(+) EMISSION FROM JUPITER

We present measurements of the mid-to-low latitude H-3(+) emission fro m Jupiter, derived from a spectroscopic study of the planet carried ou t on the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, Hawai i, on May 3-5, 1993. The measurements indicate ionospheric H-3(+) temp eratures similar to 800 K and column densities of the order of 10(11) cm(-2). The emission levels depend strongly on latitude and longitude, but are generally of the order of 10(-1) erg s(-1) cm(-2), indicating that the cooling effect of H-3(+) is a significant factor in the iono sphere. These emission levels also strongly suggest either that aurora lly produced H(3)(+)is being transported to nonauroral latitudes or th at sources in addition to solar EUV are required to produce the ionisa tion and excitation energy necessary to account for the observed H-3() emission. This view is supported by comparing the emission profiles as a function of latitude with those obtained from a jovian global cir culation model which has auroral electron precipitation and solar EUV as ionisation inputs. The spatial distribution of H-3(+) emission sugg ests that this ion may be a useful probe of Jupiter's magnetic field a t subauroral latitudes. (C) 1997 Academic Press.