Whistler Mode Waves Associated With Broadband Auroral Electron Precipitation at Jupiter

Abstract

Large amplitude electromagnetic plasma waves are observed simultaneously with intense fluxes of electrons precipitating on auroral field lines at Jupiter. Here we present plasma wave observations from the Juno Waves instrument obtained during an instance of very intense broadband electron precipitation observed by the Jupiter Energetic Particle Detector Instrument connecting to Jupiter's main auroral oval. The wave spectrum extends from 50 Hz to~10 kHz with peak-to-peak amplitudes of 10 nT in the magnetic channel and of~1 V/m in the electric channel, representing some of the most intense plasma waves observed by Juno. The E and B fields of these electromagnetic waves are correlated and have apparent polarization perpendicular to Jupiter's magnetic field with a downward Poynting flux. We conclude the plasma waves are whistler mode emissions with a possible admixture of ion-cyclotron or Alfvén waves and may be important in the broadband electron acceleration.Plain Language Summary Large amplitude whistler mode waves are found coincidently with intense fluxes of precipitating electrons across a broad energy range connecting to Jupiter's main auroral oval. The whistler mode waves are propagating downward, in the same direction as the precipitating electrons. The tight correspondence in time between the waves and the electrons strongly suggests an important interaction between the waves and electrons.

Six Pieces of Evidence Against the Corotation Enforcement Theory to Explain the Main Aurora at Jupiter

“…A closer examination of the energy transferred by Alfvén waves already showed some promising results, both theoretically (Saur et al., 2018) and observationally (Gershman et al., 2019). Moreover, other plasma waves (auroral hiss) have also been suggested as being important in the acceleration of energetic particles in Jupiter's polar region and may also be relevant for the MEs (e.g., Elliott et al., 2018; Kurth et al., 2018). Finally, it could also be of critical importance for magneto‐hydrodynamic simulations of the Jovian magnetosphere to focus on the Poynting flux and the contribution of Alfvén wave power rather than on the field‐aligned currents when comparing their outputs to auroral images in order to provide crucial insight in understanding the origin of the MEs.…”

Wave‐Particle Interactions Associated With Io's Auroral Footprint: Evidence of Alfvén, Ion Cyclotron, and Whistler Modes

“…More broadly, recent works have brought the role of Alfvén, as well as whistler-mode, waves to the fore by invoking their activity to explain the widely observed broadband, precipitating electron energy distributions and accelerated ion populations linked to Jupiter's main auroral emissions (Allegrini et al, 2017(Allegrini et al, , 2020Damiano et al, 2019;Elliott et al, 2020;Gershman et al, 2019;Kurth et al, 2018;Mauk et al, 2017aMauk et al, , 2017bMauk et al, , 2018.…”

Energy Flux and Characteristic Energy of Electrons Over Jupiter's Main Auroral Emission

“…It appears that the broad energy distributions (distributions that lack sharp peaks in energy) are the more common and dominant particle energy signature in the main auroral region (Allegrini et al, 2017; Clark et al, 2018; Mauk, Haggerty, Paranicas, Clark, Kollmann, Rymer, Mitchell et al (2017); Szalay et al, 2017, 2018). Several authors have suggested that these distributions are indicative of wave‐particle accelerations via, say, Alfvén or whistler mode waves (e.g., Elliott et al, 2018; Kurth et al, 2018; Saur et al, 2018).…”