Articles | Volume 33, issue 10
Ann. Geophys., 33, 1211–1219, 2015
Ann. Geophys., 33, 1211–1219, 2015

Regular paper 01 Oct 2015

Regular paper | 01 Oct 2015

The far-ultraviolet main auroral emission at Jupiter – Part 2: Vertical emission profile

B. Bonfond1,*, J. Gustin1, J.-C. Gérard1, D. Grodent1, A. Radioti1, B. Palmaerts2,1, S. V. Badman3, K. K. Khurana4, and C. Tao5 B. Bonfond et al.
  • 1Laboratoire de Physique Atmosphérique et Planétaire, Université de Liège, Allée du 6 Août, 19c, 4000 Liège, Belgium
  • 2Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
  • 3Lancaster University, Department of Physics, Lancaster, UK
  • 4University of California, Los Angeles, Los Angeles, California, USA
  • 5Institut de Recherche en Astrophysique et Planétologie, Toulouse, France
  • *Invited contribution by B. Bonfond, recipient of the EGU Division Outstanding Young Scientists Award 2015.

Abstract. The aurorae at Jupiter are made up of many different features associated with a variety of generation mechanisms. The main auroral emission, also known as the main oval, is the most prominent of them as it accounts for approximately half of the total power emitted by the aurorae in the ultraviolet range. The energy of the precipitating electrons is a crucial parameter to characterize the processes at play which give rise to these auroral emissions, and the altitude of the emissions directly depends on this energy. Here we make use of far-UV (FUV) images acquired with the Advanced Camera for Surveys on board the Hubble Space Telescope and spectra acquired with the Space Telescope Imaging 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-dusk sector by Galileo in the visible domain. However, a detailed analysis of the effect of hydrocarbon absorption, including both simulations and FUV spectral observations, indicates that FUV apparent vertical profiles should be considered with caution, as these observations are not incompatible with an emission peak located at 250 km. The analysis also calls for spectral observations to be carried out with an optimized geometry in order to remove observational ambiguities.

Short summary
Early models of the main auroral emission at Jupiter assumed axisymmetry, but significant local time variability is obvious on any image of the Jovian aurorae. Here we use far-UV images from the Hubble Space Telescope to further characterize these variations on a statistical basis. We show that the dusk side sector is ~3 times brighter than the dawn side, and we suggest that such an asymmetry could be the result of a partial ring current in the nightside magnetosphere.