The Jovian ionosphere

The Jovian ionosphere has been modeled for both auroral and non-auroral regions in this dissertation. The model utilizes updated data on chemical reactions of ion chemistry among ions in the ionosphere, photo-process cross sections for major neutrals and hydrocarbons, and electron impact cross sections for major neutrals in the Jovian upper atmosphere. The absorption of solar ultraviolet flux between 846 and 1116 A by H{dollar}sb2{dollar} has been calculated at high resolution, which results in previously-ignored ionization of hydrocarbons near the methane homopause by strong solar UV emission lines and the continuum flux in the wings of the H{dollar}sb2{dollar} lines. The non-auroral model shows that the Jovian ionosphere at mid-latitudes should have a hydrocarbon ion layer at lower altitudes, which may correspond to the E region in the terrestrial ionosphere.; In the auroral model, a multi-stream transport code is employed for the precipitation of 10 keV electrons into the Jovian upper atmosphere. An upper atmosphere model for auroral regions is constructed from the mid-latitude neutral atmosphere model derived from the Voyager data, modified with higher temperatures based on ground-based infrared observations of the auroral regions. It is found from the auroral model that vibrationally excited H{dollar}sb2{dollar} affects the vibrational distribution of H{dollar}sbsp{lcub}3{rcub}{lcub}+{rcub}{dollar} that can be probed by infrared emission spectra. Results of the auroral model include densities of major ions as well as vibrational distributions of H{dollar}sb2{dollar} and H{dollar}sbsp{lcub}3{rcub}{lcub}+{rcub}{dollar} as functions of altitude for the case of precipitation of 10 keV electrons with an energy flux of 1 erg cm{dollar}sp{lcub}-2{rcub}{dollar}s{dollar}sp{lcub}-1{rcub}{dollar}. The computed column densities of H{dollar}sbsp{lcub}3{rcub}{lcub}+{rcub}(vsb1 = 0,vsb2 = 1){dollar} and H{dollar}sbsp{lcub}3{rcub}{lcub}+{rcub}(vsb1 = 0,vsb2 = 2){dollar} are consistent with the infrared observations of H{dollar}sbsp{lcub}3{rcub}{lcub}+{rcub}{dollar}. Finally we investigate the time variation of ion densities in response to electron precipitation in the auroral regions. We find that the electron densities from the time-dependent auroral model could differ by up to an order of magnitude from those of steady-state models depending on the time scale of variations in the precipitating energy flux.