High-energy particles

In the Jovian magnetosphere, electrons, protons, and heavier ions are accelerated to energies well above 10 MeV. These energetic particles constitute a valuable diagnostic tool for studying magnetospheric processes and produce the Jovian radio emissions. In the inner magnetosphere, both the electron and proton fluxes with energies above 1 MeV build up to ~ 10 8 per cm 2 s and constitute a major radiation hazard to spacecraft passing through this region. Surprisingly, high fluxes of energetic oxygen and sulfur (> 7 MeV/nuc) are also found in the inner magnetosphere. Of particular interest are the interactions of these particles with the inner Jovian moons and with the Io plasma torus. Throughout much of the middle magnetosphere and magnetospheric tail, highest fluxes are found in the plasma sheet, which coincides closely with the tilted dipole equator out to 45 R j (Jupiter radii). This plasma sheet has not been identified beyond 45 R j in the subsolar hemisphere; however, on the night side, it extends to 200 R j . On the day side, fluxes near the equator are relatively independent of distance (15 to 45 R J ) and fall into the range 10 4 to 10 per cm 2 s each for protons and electrons above ~ 1 MeV. In the predawn direction, proton and electron fluxes decrease by three orders of magnitude from 20 to 90 R j (10 5 to 10 2 per cm 2 s) and then remain relatively constant to the boundary layer near the magnetopause.