Energetic Proton Acceleration Associated With Io's Footprint Tail

G. Clark, B. H. Mauk, P. Kollmann, J. R. Szalay, A. H. Sulaiman, D. J. Gershman, J. Saur, S. Janser, K. Garcia-Sage, T. Greathouse, C. Paranicas, F. Allegrini, F. Bagenal, S. J. Bolton, J. E.P. Connerney, R. W. Ebert, G. Hospodarsky, D. Haggerty, V. Hue, M. ImaiS. Kotsiaros, D. J. McComas, A. Rymer, J. Westlake

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Observations of energetic charged particles associated with Io's footprint (IFP) tail, and likely within or very near the Main Alfvén Wing, during Juno's 12th perijove (PJ) crossing show evidence of intense proton acceleration by wave-particle heating. Measurements made by Juno/JEDI reveal proton characteristics that include pitch angle distributions concentrated along the upward loss cone, broad energy distributions that span ~50 keV to 1 MeV, highly structured temporal/spatial variations in the particle intensities, and energy fluxes as high as ~100 mW/m2. Simultaneous measurements of the plasma waves and magnetic field suggest the presence of ion cyclotron waves and transverse Alfvénic fluctuations. We interpret the proton observations as upgoing conics likely accelerated via resonant interactions with ion cyclotron waves. These observations represent the first measurements of ion conics associated with moon-magnetosphere interactions, suggesting energetic ion acceleration plays a more important role in the IFP tail region than previously considered.

Original languageEnglish (US)
Article numbere2020GL090839
JournalGeophysical Research Letters
Issue number24
StatePublished - Dec 28 2020

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


  • Juno
  • Jupiter
  • aurora
  • ion conics
  • proton acceleration
  • wave-particle interactions


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