Mid-to-low latitude H⁺₃emission from Jupiter

We present measurements of the mid-to-low latitude H⁺₃emission from Jupiter, derived from a spectroscopic study of the planet carried out on the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea, Hawaii, on May 3-5, 1993. The measurements indicate ionospheric H⁺₃temperatures ~800 K and column densities of the order of 10¹¹cm^-2. The emission levels depend strongly on latitude and longitude, but are generally of the order of 10^-1erg s^-1cm^-2, indicating that the cooling effect of H⁺₃is a significant factor in the ionosphere. These emission levels also strongly suggest either that aurorally produced H⁺₃is being transported to nonauroral latitudes or that sources in addition to solar EUV are required to produce the ionisation and excitation energy necessary to account for the observed H⁺₃emission. This view is supported by comparing the emission profiles as a function of latitude with those obtained from a jovian global circulation model which has auroral electron precipitation and solar EUV as ionisation inputs. The spatial distribution of H⁺₃emission suggests that this ion may be a useful probe of Jupiter's magnetic field at subauroral latitudes.