Quasi-Periodic Variation of Jupiter's Aurora Compared with Magnetospheric Dynamics

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's northern aurora by the Earth-orbiting planetary 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 Juno's solar wind during its approaching phase 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 greater than 1.25 days is unlikely to exist between the volcanically active and quiet conditions. This is consistent with the expected difference estimated from a proposed relationship applied to the plasma variation of this volcanic event based on a theoretical model. 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. Auroral bursts with a typical duration of <10 h are seen sometimes at the peaks of the periodic variation. The burst power is positively correlated with the amplitude of the periodic variation, and the burst occurrence increases during the volcanically active period. This auroral observation links parts of previous observations to given a global view of Jupiter's magnetospheric dynamics.