Are Dawn Storms Jupiter's auroral substorms?: Clues from the Juno mission

Identified as soon as we could acquire well resolved images of the UV auroras of Jupiter with the Hubble Space Telescope, Dawn Storms are among the brightest and most spectacular auroral events on Jupiter. Their name derives from the fact that the brightest part of the sequence always takes place on the dawn side of the main auroral oval. However, recent and unprecedented observations from the Juno spacecraft, which acquires views of the aurorae from the poles and has access to the night side of the aurorae, showed us the process actually starts on the night side and continues on the dusk side (and possibly even beyond) as the planet rotates. As the number of observations increases, a pattern starts to emerge, with an initiation with faint midnight spots, then beads on the main emissions, then an
spectacular expansion and brightening of the dawn arc with an latitudinal emission void, followed the formation of a longitudinal gap the appearance of large scale injection signatures. We also noted that most dawn storms are non-isolated, meaning that they often occur in sequences separated by a few hours, and that some dawn storms do not fully develop (pseudo-dawn-storms). These morphological characteristics as well as in situ measurements carried out in the magnetosphere indicate that Dawn Storms are the auroral signatures of large scale reconfigurations of the magnetotail. While the accumulation of mass an energy in the Jovian magnetotail is related to internal processes (essentially Io’s volcanism and Jupiter’s rotation), the explosive reconfigurations of the magnetosphere which follows it bears many similarities with the terrestrial substorms, indicating that similar physics is at play.