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1st Adiabatic Invariants and Phase Space Densities for the Jovian Electron and Proton Radiation Belts-Galileo and GIRE3 Estimates
  • Henry Berry Garrett,
  • Insoo Jun
Henry Berry Garrett
California Institute of Technology
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Insoo Jun
Jet Propulsion Lab (NASA)

Corresponding Author:insoo.jun@jpl.nasa.gov

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The fluxes and phase space densities for a fixed 1st adiabatic invariant for high energy electrons and protons provide important inputs for various scientific studies for determining the physics of particle diffusion and energization. This study provides estimates of the 1st adiabatic invariant and phase space density based on the complete and large data base available from the Energetic Particle Detector (EPD) on Galileo for the jovian environment. To be specific, 10 minute averages of the high energy electron and proton data are used to compute differential flux spectra versus energy for L=~8 - 25 over the Galileo mission. These spectra provide estimates of the differential fluxes and phase space density for constant 1st adiabatic invariants between 102 to 105 MeV/G. As would be expected, the electron and proton fluxes and phase space densities generally trend lower as the planet is approached. The results indicate that, whereas the overall trends for each orbit are consistent, detailed orbit to orbit variations can be observed. Galileo orbit C22 is presented as a specific example of deviations from the mean downward trend. To validate the Galileo results and extend the findings into L=3, the GIRE3 model was also used to compute the fluxes and phase space densities for constant 1st adiabatic invariant versus L-shell. Comparison between GIRE3 and EPD demonstrates that the model adequately reproduces the EPD data trends and they consistently show additional variations near Io. This provides proof that the GIRE3 is a useful starting point for diffusion analyses and similar studies.