Juno In Situ Observations Above the Jovian Equatorial Ionosphere

P. W. Valek, F. Bagenal, R. W. Ebert, F. Allegrini, D. J. McComas, J. R. Szalay, R. J. Wilson, S. J. Bolton, J. E.P. Connerney

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5 Scopus citations


The arrival of Juno at Jupiter enables repeated in situ observations above the Jovian ionosphere. The low altitude and high velocity of Juno at perijove permits direct sampling of ionospheric ion populations. We present the first direct observations above the ionosphere made by the Jovian Auroral Distributions Experiment Ion sensor (JADE-I). When looking into the spacecraft ram direction, JADE-I can measure ion energy distributions to below 1 eV/q along with ion composition. We report observations from 17 Juno perijove passes. At these latitudes, the low energy ions consist of protons and heavier ions, protons being the dominant species. Heavy ions—primarily oxygen and sulfur likely originating from the magnetosphere—are seen each pass, but their intensity varies. Other trace light ions are observed during some of the perijoves: H3+ (6 of 17 perijoves), He+ (2 of 17 perijoves). Ionospheric ions are observed up to altitudes of ~7,000 km.

Original languageEnglish (US)
Article numbere2020GL087623
JournalGeophysical Research Letters
Issue number12
StatePublished - Jun 28 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


  • Jupiter
  • equatorial
  • in situ
  • ionosphere
  • ions


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