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

Abstract

Large-scale electrical currents and Alfvénic 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 Alfvénic 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 Alfvénic wave power could be an important source in driving Jupiter's aurorae, as theoretically predicted.