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. ImaiStavros Kotsiaros, D. J. McComas, A. Rymer, J. Westlake

*Corresponding author for this work

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Abstract

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
Article numbere2020GL090839
JournalGeophysical Research Letters
Volume47
Issue number24
ISSN0094-8276
DOIs
Publication statusPublished - 2020

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