We define the spatial clustering of X-rays within Jupiter’s northern auroral regions by classifying their distributions into ‘X-ray auroral structures’. Using data from Chandra during Juno’s main mission observations (24 May 2016 – 8 September 2019), we define five X-ray structures based on their ionospheric location and calculate the distribution of auroral photons. The morphology and ionospheric location of these structures allow us to explore the possibility of numerous X-ray auroral magnetospheric drivers. We compare these distributions to Hubble Space Telescope (HST)and Juno (Waves and MAG) data, and a 1D solar wind propagation model to infer the state of Jupiter’s magnetosphere. Our results suggest that the five sub-classes of ‘X-ray structures’ fall under two broad morphologies: fully polar and low latitude emissions. Visibility modelling of each structure suggests the non-uniformity of the photon distributions across the Chandra intervals are likely associated with the switching on/off of magnetospheric drivers as opposed to geometrical effects. The combination of ultraviolet (UV) and X-ray morphological structures is a powerful tool to elucidate the behaviour of both electrons and ions and their link to solar wind/magnetospheric conditions in the absence of an upstream solar monitor.

Dawn storms are among the brightest events in the Jovian aurorae. Up to now, they had only been observed from Earth-based observatories, only showing the Sun-facing side of the planet. Here we show for the first time global views of the phenomenon, from its initiation to its end and from the nightside of the aurora onto the dayside. Based on Juno's first 20 orbits, some patterns now emerge. Small short-lived spots are often seen for a couple of hours before the main emission starts to brighten and evolve from a straight arc to a more irregular one in the midnight sector. As the whole feature rotates dawn-ward, the arc then separates into two arcs with a central initially void region that is progressively filled with emissions. A gap in longitude then often forms before the whole feature dims. Finally, it transforms into an equatorward-moving patch of auroral emissions associated with plasma injection signatures. Some dawn storms remain weak and never fully develop. We also found cases of successive dawn storms within a few hours. Dawn storm thus share many fundamental features with the auroral signatures of the substorms at Earth. These findings demonstrate that, whatever their sources, mass and energy do not always circulate smoothly in planetary magnetospheres. Instead they often accumulate until the magnetospheres reconfigure and generate substorm-like responses in the planetary aurorae, although the temporal and spatial scales are different for different planets.

Quasi-periodic variations of a few to several days are observed in the energetic plasma and magnetic dipolarization in Jupiter’s magnetosphere. Variation in the plasma mass flux related to Io’s volcanic activity is proposed as a candidate of the variety of the period. Using a long-term monitoring of Jupiter by the Earth-orbiting space telescope Hisaki, we analyzed the quasi-periodic variation seen in the auroral power integrated over the northern pole for 2014–2016, which included monitoring Io’s volcanically active period in 2015 and the solar wind near Jupiter during Juno’s approach in 2016. Quasi-periodic variation with periods of 0.8–8 days was detected. The difference between the periodicities during volcanically active and quiet periods is not significant. Our dataset suggests that a difference of period between this volcanically active and quiet conditions is below 1.25 days. This is consistent with the expected difference estimated from a proposed relationship based on a theoretical model applied to the plasma variation of this volcanic event. The periodicity does not show a clear correlation with the auroral power, central meridional longitude, or Io phase angle. The periodic variation is continuously observed in addition to the auroral modulation due to solar wind variation. Furthermore, Hisaki auroral data sometimes shows particularly intense auroral bursts of emissions lasting <10h. We find that these bursts coincide with peaks of the periodic variations. Moreover, the occurrence of these bursts increases during the volcanically active period. This auroral observation links parts of previous observations to give a global view of Jupiter’s magnetospheric dynamics.