Hourly Periodic Variations of Ultralow-Frequency (ULF) Waves in Jupiter's Magnetosheath

Abstract

Periodic variations are widely identified in the Jovian system, varying from 10 s of seconds to several days or even longer. These processes are strongly influenced by solar wind conditions, planetary rotation and Io's volcanic activity. Ultralow-frequency (ULF) waves at 10 s of minutes, which are the typical time scale of field-line resonance, are considered as a crucial process in driving the Jovian energy circulation. The longer time-scale periodicities are likely associated with global mass circulation. In this study, we focus on multihour variations of the ULF wave energy, which are difficult to identify within the magnetosphere due to the rapid planetary rotation modulation. Using the magnetic field observations from Juno and Galileo in Jupiter's magnetosheath, we found multiple significant multihour periodicities, widely distributed from 2 to 10 hr, peaked at different values from case to case. The most common periodicities were between 3 and 5 hr, existing in both the dawn and dusk sides. These common periodicities are likely associated with the energy transport from the inside to the magnetosheath.