Ultralow-Frequency Waves in Driving Jovian Aurorae Revealed by Observations From HST and Juno

Large-scale electrical currents and Alfvenic waves are the two main drivers responsible for producing planetary aurorae. The relative contribution of each process is a central question in terrestrial auroral science, and poorly understood for other planets due to the relatively rare opportunity of in-situ spacecraft measurements. Here, we present observations of Jupiter's aurorae from the Hubble Space Telescope (HST) contemporaneous with Juno magnetometer measurements in the magnetosphere. For three successive days, we found that the magnetospheric ultralow-frequency (ULF) wave activity (with periods of 1-60 min) was correlated with auroral power. This was especially true for the Alfvenic modes. We further performed a statistical analysis based on HST visits during Juno's third and seventh orbit, which revealed a systematic correlation between ULF wave and auroral activity. Our results imply that Alfvenic wave power could be an important source in driving Jupiter's aurorae, as theoretically predicted. Plain Language Summary Jupiter has the most powerful aurora in our solar system, reflecting the intense energy dissipation in the largest planetary magnetosphere. It is still an open question on how auroral particles are accelerated at a planet. At Earth, there are two prestigious mechanisms for auroral acceleration, which are wave-particle interaction and electrical potential drop. Recent Juno observations have been shown direct evidence on both wave-particle interaction and electrical potential drop in the auroral region. However, the importance of wave-particle interaction on Jovian aurora still remains unclear. In this study, we reveal a systematic correlation between aurora and magnetospheric waves using the large campaign of Hubble Space Telescope during the NASA Juno mission. The results can significantly improve our understanding on wave-particle interaction in driving Jovian aurora.