Properties of electrons accelerated by the Ganymede-magnetosphere interaction: survey of Juno high-latitude observations
Journal of Geophysical Research: Space Physics(2024)
摘要
The encounter between the Jovian co-rotating plasma and Ganymede gives rise
to electromagnetic waves that propagate along the magnetic field lines and
accelerate particles by resonant or non-resonant wave-particle interaction.
They ultimately precipitate into Jupiter's atmosphere and trigger auroral
emissions. In this study, we use Juno/JADE, Juno/UVS data, and magnetic field
line tracing to characterize the properties of electrons accelerated by the
Ganymede-magnetosphere interaction in the far-field region. We show that the
precipitating energy flux exhibits an exponential decay as a function of
downtail distance from the moon, with an e-folding value of 29,
consistent with previous UV observations from the Hubble Space Telescope (HST).
We characterize the electron energy distributions and show that two
distributions exist. Electrons creating the Main Alfvén Wing (MAW) spot and
the auroral tail always have broadband distribution and a mean characteristic
energy of 2.2 keV while in the region connected to the Transhemispheric
Electron Beam (TEB) spot the electrons are distributed non-monotonically, with
a higher characteristic energy above 10 keV. Based on the observation of
bidirectional electron beams, we suggest that Juno was located within the
acceleration region during the 11 observations reported. We thus estimate that
the acceleration region is extended, at least, between an altitude of 0.5 and
1.3 Jupiter radius above the 1-bar surface. Finally, we estimate the size of
the interaction region in the Ganymede orbital plane using far-field
measurements. These observations provide important insights for the study of
particle acceleration processes involved in moon-magnetosphere interactions.
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