Broadband Energization of Superthermal Electrons in Jupiter’s Inner Magnetosphere

The Juno spacecraft in a polar orbit around Jupiter has observed broadband electron energization signatures at high latitudes (Mauk et al., 2017, https://doi.org/10.1038/nature23648). We investigate the origin of this energization by simulating the propagation of dispersive Alfvén waves from the Io...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2022-08, Vol.127 (8), p.n/a
Main Authors: Coffin, Drew, Damiano, Peter, Delamere, Peter, Johnson, Jay, Ng, Chung‐Sang
Format: Article
Language:English
Subjects:
Alfven waves
Amplitudes
Auroral emissions
Auroras
Broadband
dispersive Alfvén waves
electron acceleration
Electron beams
Energy budget
Energy flux
Hot electrons
Initial conditions
Ionosphere
Jupiter
Jupiter probes
kinetic simulation
Magnetic fields
Magnetohydrodynamic waves
magnetosphere
Particle energy
Perturbation
Planetary atmospheres
Planetary magnetospheres
Planets
Polar orbits
Populations
Simulation
Spacecraft
Toruses
Transverse waves
Wave propagation
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Summary:The Juno spacecraft in a polar orbit around Jupiter has observed broadband electron energization signatures at high latitudes (Mauk et al., 2017, https://doi.org/10.1038/nature23648). We investigate the origin of this energization by simulating the propagation of dispersive Alfvén waves from the Io plasma torus to high latitudes. These waves may be triggered by mechanisms such as the moon‐magnetosphere interaction or inflows from radial transport. We build on the initial hybrid gyrofluid‐kinetic electron simulation of Damiano et al. (2019, https://doi.org/10.1029/2018gl081219) to further quantify electron energization by Alfvénic waves, and investigate this process as a local source mechanism for observed broadband superthermal electron populations. We find that the magnitude of energization increases with the wave amplitude, while decreasing the radial wavelength reduces the high‐latitude wave and particle energy flux. Over the examined range of initial conditions we successfully generate broadband electron populations consistent with Juno observations (Mauk et al., 2017, http://doi.org/10.1038/nature23648; Szalay et al., 2018, https://doi.org/10.1029/2018je005752), that contribute to both precipitating populations and those that form trans‐hemispheric beams. Our energized electron distributions are consistent with observed superthermal populations critical for the torus energy budget (Bagenal & Delamere, 2011, https://doi.org/10.1029/2010ja016294) and Io‐related auroral emission. Plain Language Summary The Juno spacecraft, orbiting Jupiter, has observed energized electrons displaying a broad spectrum of energies close to the planet's poles. We seek an explanation for these energetic electrons by simulating Alfvén waves (transverse waves analogous to waves on a string) generated in Jupiter's magnetosphere. These waves carry energy originating from flow‐induced disturbances in the Io plasma torus to the planet's ionosphere, traveling along magnetic field lines. We find that close to the planet's ionosphere, Alfvén waves accelerate electrons in a manner consistent with the Juno observations. These energized particles then can move along the field line, either into the planet's atmosphere with key consequences for aurora, or down to the torus and beyond to produce the observed hot electron population required to explain the torus energy budget. We vary the amplitude of our initial Alfvén wave‐producing perturbations to show that a stronger wave results in st
ISSN:2169-9380
2169-9402
DOI:10.1029/2022JA030528