First Adiabatic Invariants and Phase Space Densities for the Jovian Electron and Proton Radiation Belts—Galileo and GIRE3 Estimates

Abstract

AbstractThe fluxes and phase space densities for a fixed first 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 first 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 min averages of the high‐energy electron and proton data are used to compute differential flux spectra versus energy between L = 8 and 25 over the mission. These spectra provide estimates of the differential fluxes and phase space density for constant first adiabatic invariants between 102 and 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 an 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 first 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.