AUTHOR=Clark G. , Szalay J. R. , Sulaiman A. H. , Saur J. , Kollmann P. , Mauk B. H. , Paranicas C. , Hue V. , Greathouse T. , Allegrini F. , Glocer A. , Garcia-Sage K. , Bolton S. 

TITLE=Energetic proton acceleration by EMIC waves in Io’s footprint tail

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2023.1016345

DOI=10.3389/fspas.2023.1016345

ISSN=2296-987X

ABSTRACT=In this contribution, we present a survey of energetic proton observations associated with Io’s footprint tail (FPT) and compare their signatures with in-situ measurements of the plasma waves and lower-energy electron environment. We find further supporting evidence that proton acceleration in Io’s FPT is likely a consequence of wave-particle interactions via electromagnetic ion cyclotron waves that are generated by precipitating electrons into Jupiter’s ionosphere. This idea was originally proposed by (Clark et al., 2020; Sulaiman et al., 2020) based on NASA’s Juno mission likely transiting Io’s Main Alfvén Wing (MAW) during its twelfth orbit (i.e., PJ12). Additionally, the analysis of > 50 keV protons presented here highlights important observational details about the Io-Jupiter interaction, such as: 1) proton acceleration in Io’s FPT is a persistent feature and the energy flux carried by the protons are highest at smaller Io-Alfvén tail distances; 2) energetic protons exhibit positive correlations to both plasma waves and < 100 keV/Q electrons; 3) during a small number of Io FPT crossings, the protons display finer spatial/temporal structure reminiscent of the electron observations reported by Szalay et al. (2018); and 4) the proton pitch angle distributions are characterized by two types: conic distributions in, or near, Io’s MAW and isotropic, elsewhere.