Maïté Dumont

Jupiter's equatorward auroral features: possible signatures of magnetospheric injections

The present study investigates the characteristics of ultraviolet auroral features located equatorward of the main emission appearing in Hubble Space Telescope images of the northern and southern Jovian hemispheres obtained in 2000–2007. On average, one feature is observed every day, but several auroral structures are occasionally seen over a wide range of local times in the same image. Several properties of these features are analyzed, such as their location, emitted power, and lifetime. Additionally, we magnetically map the auroral features to the equatorial plane using the VIPAL model in order to compare their observed properties with those of magnetospheric injections detected by the Galileo spacecraft. The equatorward auroral features show up between the Io footpath and the main auroral emission, at all System III longitudes, in agreement with Galileo measurements. Moreover, we compare the magnetic flux associated with these features with estimates of the outgoing flux related to the radial transport of plasma in the Jovian magnetosphere, and we find that they could account for at least one third of this flux. This comparative study shows that the auroral features under study are most probably related to magnetospheric injections and thus sheds light on the processes involved in the magnetosphere-ionosphere dynamics.

Jupiter's Aurora Observed With HST During Juno Orbits 3 to 7

A large set of observations of Jupiters ultraviolet aurora was collected with the Hubble Space Telescope concurrently with the NASA‐Juno mission, during an eight‐month period, from 30 November 2016 to 18 July 2017. These Hubble observations cover Juno orbits 3 to 7 during which Juno in situ and remote sensing instruments, as well as other observatories, obtained a wealth of unprecedented information on Jupiters magnetosphere and the connection with its auroral ionosphere. Jupiters ultraviolet aurora is known to vary rapidly, with timescales ranging from seconds to one Jovian rotation. The main objective of the present study is to provide a simplified description of the global ultraviolet auroral morphology that can be used for comparison with other quantities, such as those obtained with Juno. This represents an entirely new approach from which logical connections between different morphologies may be inferred. For that purpose, we define three auroral subregions in which we evaluate the auroral emitted power as a function of time. In parallel, we define six auroral morphology families that allow us to quantify the variations of the spatial distribution of the auroral emission. These variations are associated with changes in the state of the Jovian magnetosphere, possibly influenced by Io and the Io plasma torus and by the conditions prevailing in the upstream interplanetary medium. This study shows that the auroral morphology evolved differently during the five ~2 week periods bracketing the times of Juno perijove (PJ03 to PJ07), suggesting that during these periods, the Jovian magnetosphere adopted various states.