Strong whistler mode waves observed in the vicinity of Jupiter\u2019s moons

Y Y Shprits,D A Gurnett,M De Soria-Santacruz,A Y Drozdov,J D Menietti,E E Woodfield,T F Averkamp,C Paranicas,R B Horne,H Garrett,J B Groene

doi:10.1038/s41467-018-05431-x

Abstract

Understanding of wave environments is critical for the understanding of how particles are accelerated and lost in space. This study shows that in the vicinity of Europa and Ganymede, that respectively have induced and internal magnetic fields, chorus wave power is significantly increased. The observed enhancements are persistent and exceed median values of wave activity by up to 6 orders of magnitude for Ganymede. Produced waves may have a pronounced effect on the acceleration and loss of particles in the Jovian magnetosphere and other astrophysical objects. The generated waves are capable of significantly modifying the energetic particle environment, accelerating particles to very high energies, or producing depletions in phase space density. Observations of Jupiter’s magnetosphere provide a unique opportunity to observe how objects with an internal magnetic field can interact with particles trapped in magnetic fields of larger scale objects.

Highlights

Understanding of wave environments is critical for the understanding of how particles are accelerated and lost in space
While the dynamics of the magnetosphere of Earth are driven by the solar wind, the Jovian magnetosphere is believed to be internally driven by the interchange instability which results from the loading of hot plasma from volcanic eruptions on Io
In the magnetosphere of Saturn, strong waves were observed in the vicinity of Rhea[10] and Enceladus[20]

Summary

Introduction

Understanding of wave environments is critical for the understanding of how particles are accelerated and lost in space. This study shows that in the vicinity of Europa and Ganymede, that respectively have induced and internal magnetic fields, chorus wave power is significantly increased. Observations of Jupiter’s wave and particle environments near the moons allows us to directly observe how smaller magnetized or magnetically active objects interact with larger scale magnetospheric systems, and to understand the physics behind these interactions. Moons can cause loss of particles due to sweeping and absorption effects[9], but can produce a strong loss by generating waves that scatter particles in pitch angle[10]. Our current study shows that induced waves ~1 nT in wave amplitude are strong enough to produce significant modifications to the wave and particle environment. Induced waves may either scatter particles and produce strong pitch angle diffusion[11,12], or cause acceleration to relativistic or ultra-relativistic energies

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Results

Conclusion