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Jupiter’s low-altitude auroral zones: Fields, particles, plasma waves, and density depletions
  • +18
  • Ali H. Sulaiman,
  • Frederic Allegrini,
  • George Clark,
  • Randy Gladstone,
  • Stavros Kotsiaros,
  • William S Kurth,
  • Barry H. Mauk,
  • Jamey R. Szalay,
  • Fran Bagenal,
  • Bertrand Bonfond,
  • John E. P. Connerney,
  • Robert Wilkes Ebert,
  • Sadie Suzanne Elliott,
  • Daniel J Gershman,
  • George Blair Hospodarsky,
  • Vincent Hue,
  • Robert L. Lysak,
  • Adam Masters,
  • Ondrej Santolik,
  • Joachim Saur,
  • Scott J Bolton
Ali H. Sulaiman
University of Iowa

Corresponding Author:[email protected]

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Frederic Allegrini
Southwest Research Institute
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George Clark
Johns Hopkins University Applied Physics Laboratory
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Randy Gladstone
Southwest Research Institute
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Stavros Kotsiaros
NASA Goddard Space Flight Center
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William S Kurth
University of Iowa
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Barry H. Mauk
Johns Hopkins University
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Jamey R. Szalay
Princeton University
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Fran Bagenal
University of Colorado Boulder
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Bertrand Bonfond
Université de Liège
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John E. P. Connerney
NASA Goddard Space Flight Center
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Robert Wilkes Ebert
Southwest Research Institute
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Sadie Suzanne Elliott
University of Minnesota
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Daniel J Gershman
NASA Goddard Space Flight Center
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George Blair Hospodarsky
University of Iowa
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Vincent Hue
SWRI
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Robert L. Lysak
University of Minnesota
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Adam Masters
Imperial College London
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Ondrej Santolik
Department of Space Physics, Institute of Atmospheric Physics of the Czech Academy of Sciences
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Joachim Saur
University of Cologne
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Scott J Bolton
Southwest Research Institute
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Abstract

The Juno spacecraft’s polar orbits have enabled direct sampling of Jupiter’s low-altitude auroral field lines. While various datasets have identified unique features over Jupiter’s main aurora, they are yet to be analyzed altogether to determine how they can be reconciled and fit into the bigger picture of Jupiter’s auroral generation mechanisms. Jupiter’s main aurora has been classified into distinct “zones”, based on repeatable signatures found in energetic electron and proton spectra. We combine fields, particles, and plasma wave datasets to analyze Zone-I and Zone-II, which are suggested to carry the upward and downward field-aligned currents, respectively. We find Zone-I to have well-defined boundaries across all datasets. H+ and/or H3+ cyclotron waves are commonly observed in Zone-I in the presence of energetic upward H+ beams and downward energetic electron beams. Zone-II, on the other hand, does not have a clear poleward boundary with the polar cap, and its signatures are more sporadic. Large-amplitude solitary waves, which are reminiscent of those ubiquitous in Earth’s downward current region, are a key feature of Zone-II. Alfvénic fluctuations are most prominent in the diffuse aurora and are repeatedly found to diminish in Zone-I and Zone-II, likely due to dissipation, at higher altitudes, to energize auroral electrons. Finally, we identify sharp and well-defined electron density depletions, by up to two orders of magnitude, in Zone-I, and discuss their important implications for the development of parallel potentials, Alfvénic dissipation, and radio wave generation.