Surveying Quasi-Periodic Ultra-Low-Frequency Waves in the Jovian Magnetosphere

Ultra-low-frequency (ULF) pulsations of unknown origin have been observed throughout Jupiter's magnetosphere since the Pioneer era. The enormous Jovian magnetospheric cavity is capable of supporting magnetohydrodynamic (MHD) waves of periods of order tens of minutes, which may be responsible. Previous studies of such pulsations are scattered between different datasets (magnetic field, particle burst, radio and auroral electromagnetic emission intensity) and often focus on individual case studies, leaving the spatial distribution, era dependence and driving mechanism(s) of these waves an ongoing mystery. We present a global heritage survey of ULF waves using magnetometer data from the Galileo spacecraft and several near-equatorial flyby missions. We found several-hundred wave events consisting of wave packets parallel or transverse to the mean magnetic field, interpreted as fast-mode or Alfvénic MHD wave activity, respectively. Parallel and transverse events were often coincident in space and time, which may be evidence of global Alfvénic resonances of the magnetic field known as field-line-resonances. We found that 15-, 30- and 40-minute periods dominate the Jovian ULF wave spectrum, in agreement with the dominant "magic frequencies" often reported in existing literature. Events occurred predominately in the outer magnetosphere close to the magnetopause, or in the magnetotail, supporting hypotheses that ULF wave power may be driven by Kelvin-Helmholtz instabilities and other large-scale compressive perturbations on the magnetopause. ULF waves have been shown to play an important role in magnetospheric dynamics in the terrestrial magnetosphere via several wave-particle interaction mechanisms. We will discuss how these results inform the scope of potential ULF MHD wave driving mechanisms, and to what extent ULF waves influence magnetospheric dynamics at Jupiter.