The Influence of Io's 2015 Volcanic Activity on Jupiter's Magnetospheric Dynamics

Abstract Embedded deep inside the huge magnetosphere of Jupiter, the moon Io has active volcanos. Jovian magnetospheric dynamics are driven by the expulsion of Iogenic plasma in the strongly magnetized, fast‐rotating system and should vary in response to Io's volcanic activity. In early 2015 when various observations indicated an increase in volcanic activity, the EXCEED instrument onboard the Hisaki spacecraft continuously observed the Jovian magnetosphere via the aurora emission and the emission from the Io plasma torus. The plasma diagnosis of the enhanced Io plasma torus spectrum along with a physical chemistry model for deducing plasma parameters revealed a higher plasma density and a 2–4 times faster radial flow as compared with a volcanically quiet period. Aurora emissions reflecting midmagnetospheric activities showed multiple highly elevated brightness peaks about a month later. Long‐term and continuous monitoring by Hisaki enabled the first comprehensive observations of the Jovian magnetosphere in response to Io's enhanced volcanic activity.