Numerical simulation of Juno JEDI's response to high energy electrons and protons at Jupiter

<p>The Jupiter Energetic Particle Detector Instrument (JEDI) on the Juno mission detects energetic electrons from the tens of keV to almost 1 MeV and energetic ions from the tens of keV to about 10 MeV or more. The population at higher energies, e.g., > 1 MeV electrons, while relatively small in number can add non-insignificant counts in the energy range JEDI is designed to detect as foreground. For example, a band is often seen in the electron spectrograms around 200 keV that is believed to be due to higher energy electrons that for various reasons only deposit a fraction of their energy in the detector. To apply a correction to this, Mauk et al. [JGR, 2018] have developed a procedure for correcting the JEDI-measured electron spectra contaminated with high-energy foreground electrons that penetrate the detector. Using this procedure, one can extract an energy spectrum from the tens of keV to 1 MeV that corrects for both penetrators and the loss of JEDI efficiency just below 1 MeV. The corrected spectra can also be extended above 1 MeV by making use of the penetrator counts, but uncertainties exist in creating a high-energy tail.  In addition, JEDI proton data may also be contaminated with ions. To extract accurate electron spectra that extend to high energies and understand the response to penetrating protons, one would need to better understand the response of the detector to those high-energy electrons and protons. Characterization of energetic particles above 1 MeV can enable a study of energetic particles’ dynamics and structure<strong> </strong>as a function of latitude and L-shell and help evaluate different theories for loss and acceleration mechanisms. It is also a critical step in reducing uncertainties in the Jovian radiation models, assisting in understanding Juno data, and impacting future missions to Jupiter.</p> <p>A series of comprehensive and realistic Geant4 simulations have been performed to obtain the Geometric Factors (GFs) of JEDI as functions of the energy and the angles of incoming electrons and protons at a breadth that is not feasible through laboratory measurements. The results of the simulations are presented in this paper. The GFs are used to convert the count rate measurements to more physically meaningful particle flux spectra. Here, we also show the long-term trend of thus-obtained electron and proton spectra during Juno’s PJ 1 to 24.  </p>