The aurorae at Jupiter are made up of many different features associated witha variety of generation mechanisms. The main auroral emission, also known asthe main oval, is the most prominent of them as it accounts for approximatelyhalf of the total power emitted by the aurorae in the ultraviolet range. Theenergy of the precipitating electrons is a crucial parameter to characterizethe processes at play which give rise to these auroral emissions, and thealtitude of the emissions directly depends on this energy. Here we make useof far-UV (FUV) images acquired with the Advanced Camera for Surveys on boardthe Hubble Space Telescope and spectra acquired with the Space TelescopeImaging Spectrograph to measure the vertical profile of the main emissions.The altitude of the brightness peak as seen above the limb is ~ 400 km,which is significantly higher than the 250 km measured in the post-dusksector by Galileo in the visible domain. However, a detailed analysis of theeffect of hydrocarbon absorption, including both simulations and FUV spectralobservations, indicates that FUV apparent vertical profiles should beconsidered with caution, as these observations are not incompatible with anemission peak located at 250 km. The analysis also calls for spectralobservations to be carried out with an optimized geometry in order to removeobservational ambiguities.
展开▼
