µASC observations of Jovian energetic electrons interaction with Europa moon

Abstract

Since Juno’s orbit insertion, the attitude reference for the MAG investigation onboard Juno, the micro Advanced Stellar Compass (µASC), and as a part of its additional functionality, continuously measures high energy electron fluxes in Jupiter’s magnetosphere. The µASC camera head unit (CHU) sensitivity to electrons with kinetic energy greater than 15 MeV and protons with energies >80MeV, provides a means of in-situ mapping of electron fluxes sampled during 47 Juno orbits.The focus of this study are events observed when Juno is traversing M-shell of the Galilean moon, Europa, which shows distinctly different signature from that the other moons.We present µASC observations of energetic electrons interaction with Europa moon. Europa generates a wake, that affect the high energy electron driftshell, by scattering electrons into the loss-cone. The wake is then dissolved and these interactions are observed around 20° down tail. On the upstream side, the energetic drift shell is free from hard radiation as Europa acts as an obstacle for the energetic electrons. This assymetry result in a lower electon density on the upstream side resulting in an E-field filling in the e- population from surrounding driftshells in less than 10°.